viscosity experiment dependent variable

The SI unit of viscosity is the pascal second [Pa s], which has no special name. Despite its self-proclaimed title as an international system, the International System of Units has had little international impact on viscosity. The pascal second is more rare than it should be in scientific and technical writing today. The most common unit of viscosity is the dyne second per square centimeter [dyne s/cm 2 ], which is given the name poise [P] after the French physiologist Jean Poiseuille (1799–1869). Ten poise equal one pascal second [Pa s] making the centipoise [cP] and millipascal second  [mPa s] identical.

kinematic viscosity

There are actually two quantities that are called viscosity. The quantity defined above is sometimes called dynamic viscosity , absolute viscosity , or simple viscosity to distinguish it from the other quantity, but is usually just called viscosity. The other quantity called kinematic viscosity (represented by the Greek letter ν "nu") is the ratio of the viscosity of a fluid to its density.

Kinematic viscosity is a measure of the resistive flow of a fluid under the influence of gravity. It is frequently measured using a device called a capillary viscometer — basically a graduated can with a narrow tube at the bottom. When two fluids of equal volume are placed in identical capillary viscometers and allowed to flow under the influence of gravity, the more viscous fluid takes longer than the less viscous fluid to flow through the tube. Capillary viscometers will be discussed in more detail later in this section.

The SI unit of kinematic viscosity is the square meter per second [m 2 /s], which has no special name. This unit is so large that it is rarely used. A more common unit of kinematic viscosity is the square centimeter per second [cm 2 /s], which is given the name stokes [St] after the Irish mathematician and physicist George Stokes (1819–1903). One square meter per second is equal to ten thousand stokes.

Even this unit is a bit too large, so the most common unit is probably the square millimeter per second [mm 2 /s] or the centistokes [cSt]. One square meter per second is equal to one million centistokes.

The stokes is a rare example of a word in the English language where the singular and plural forms are identical. Fish is the most immediate example of a aword that behaves like this. 1 fish, 2 fish, red fish, blue fish; 1 stokes, 2 stokes, some stokes, few stokes.

factors affecting viscosity

This part needs to be reorganized.

Viscosity is first and foremost a function of material. The viscosity of water at 20 °C is 1.0020 millipascal seconds (which is conveniently close to one by coincidence alone). Most ordinary liquids have viscosities on the order of 1 to 1000 mPa s, while gases have viscosities on the order of 1 to 10 μPa s. Pastes, gels, emulsions, and other complex liquids are harder to summarize. Some fats like butter or margarine are so viscous that they seem more like soft solids than like flowing liquids. Molten glass is extremely viscous and approaches infinite viscosity as it solidifies. Since the process is not as well defined as true freezing, some believe (incorrectly) that glass may still flow even after it has completely cooled, but this is not the case. At ordinary temperatures, glasses are as solid as true solids.

From everyday experience, it should be common knowledge that viscosity varies with temperature. Honey and syrups can be made to flow more readily when heated. Engine oil and hydraulic fluids thicken appreciably on cold days and significantly affect the performance of cars and other machinery during the winter months. In general, the viscosity of a simple liquid decreases with increasing temperature. As temperature increases, the average speed of the molecules in a liquid increases and the amount of time they spend "in contact" with their nearest neighbors decreases. Thus, as temperature increases, the average intermolecular forces decrease. The actual manner in which the two quantities vary is nonlinear and changes abruptly when the liquid changes phase.

Viscosity is normally independent of pressure, but liquids under extreme pressure often experience an increase in viscosity. Since liquids are normally incompressible, an increase in pressure doesn't really bring the molecules significantly closer together. Simple models of molecular interactions won't work to explain this behavior and, to my knowledge, there is no generally accepted more complex model that does. The liquid phase is probably the least well understood of all the phases of matter.

While liquids get runnier as they get hotter, gases get thicker. (If one can imagine a "thick" gas.) The viscosity of gases increases as temperature increases and is approximately proportional to the square root of temperature. This is due to the increase in the frequency of intermolecular collisions at higher temperatures. Since most of the time the molecules in a gas are flying freely through the void, anything that increases the number of times one molecule is in contact with another will decrease the ability of the molecules as a whole to engage in the coordinated movement. The more these molecules collide with one another, the more disorganized their motion becomes. Physical models, advanced beyond the scope of this book, have been around for nearly a century that adequately explain the temperature dependence of viscosity in gases. Newer models do a better job than the older models. They also agree with the observation that the viscosity of gases is roughly independent of pressure and density. The gaseous phase is probably the best understood of all the phases of matter.

Since viscosity is so dependent on temperature, it shouldn't never be stated without it.

This is a pretty good model for liquids…

η =  Ae B / T

y  =  b  +  mx

Motor oil is like every other fluid in that its viscosity varies with temperature and pressure. Since the conditions under which most automobiles will be operated can be anticipated, the behavior of motor oil can be specified in advance. In the United States, the organization that sets the standards for the performance of motor oils is the Society of Automotive Engineers (SAE). The SAE numbering scheme describes the behavior of motor oils under low and high temperature conditions — conditions that correspond to starting and operating temperatures. The first number, which is always followed by the letter W for winter, describes the low temperature behavior of the oil at start up while the second number describes the high temperature behavior of the oil after the engine has been running for some time. Lower SAE numbers describe oils that are meant to be used under lower temperatures. Oils with low SAE numbers are generally runnier (less viscous) than oils with high SAE numbers, which tend to be thicker (more viscous).

For example, 10W‑40 oil would have a viscosity no greater than 7,000 mPa s in a cold engine crankcase even if its temperature should drop to −25 °C on a cold winter night and a viscosity no less than 2.9 mPa s in the high pressure parts of an engine near the point of overheating (150 °C).

capillary viscometer

The the mathematical expression describing the flow of fluids in circular tubes was determined by the French physician and physiologist Jean Poiseuille (1799–1869). Since it was also discovered independently by the German hydraulic engineer Gotthilf Hagen (1797–1884), it should be properly known as the Hagen-Poiseuille equation , but it is usually just called Poiseuille's equation . I will not derive it here (but I probably should someday). For non-turbulent, non-pulsatile fluid flow through a uniform straight pipe, the volume flow rate ( q m ) is…

• directly proportional to the pressure difference ( ∆ P ) between the ends of the tube
• inversely proportional to the length ( ℓ ) of the tube
• inversely proportional to the viscosity ( η ) of the fluid
• proportional to the fourth power of the radius ( r 4 ) of the tube

Solve for viscosity if that's what you want to know.

Capillary viscometer… keep writing… sorry this is incomplete.

falling sphere

The mathematical expression describing the viscous drag force on a sphere was determined by the 19th century British physicist George Stokes . I will not derive it here (but I probably should someday in the future).

R  = 6πη rv

The formula for the buoyant force on a sphere is accredited to the Ancient Greek engineer Archimedes of Syracuse , but equations weren't invented back then.

B  = ρ fluid gV displaced

The formula for weight had to be invented by someone, but I don't know who.

W  =  mg  = ρ object gV object

Let's combine all these things together for a sphere falling in a fluid. Weight points down, buoyancy points up, drag points up. After a while, the sphere will fall with constant velocity. When it does, all these forces cancel. When a sphere is falling through a fluid it is completely submerged, so there is only one volume to talk about — the volume of a sphere. Let's work through this.

And here we are.

Drop a sphere into a liquid. If you know the size and density of the sphere and the density of the liquid, you can determine the viscosity of the liquid. If you don't know the density of the liquid you can still determine the kinematic viscosity. If you don't know the density of the sphere, but you know its mass and radius, well then you can calculate its density.

non-newtonian fluids

Newton's equation relates shear stress and velocity gradient by means of a quantity called viscosity. A newtonian fluid is one in which the viscosity is just a number. A non-newtonian fluid is one in which the viscosity is a function of some mechanical variable like shear stress or time. Non-newtonian fluids that change over time are said to have a memory .

Some gels and pastes behave like a fluid when worked or agitated and then settle into a nearly solid state when at rest. Such materials are examples of shear-thinning fluids. House paint is a shear-thinning fluid and it's a good thing, too. Brushing, rolling, or spraying are means of temporarily applying shear stress. This reduces the paint's viscosity to the point where it can now flow out of the applicator and onto the wall or ceiling. Once this shear stress is removed the paint returns to its resting viscosity, which is so large that an appropriately thin layer behaves more like a solid than a liquid and the paint does not run or drip. Think about what it would be like to paint with water or honey for comparison. The former is always too runny and the latter is always too sticky.

Toothpaste is another example of a material whose viscosity decreases under stress. Toothpaste behaves like a solid while it sits at rest inside the tube. It will not flow out spontaneously when the cap is removed, but it will flow out when you put the squeeze on it. Now it ceases to behave like a solid and starts to act like a thick liquid. when it lands on your toothbrush, the stress is released and the toothpaste returns to a nearly solid state. You don't have to worry about it flowing off the brush as you raise it to your mouth.

Shear-thinning fluids can be classified into one of three general groups. A material that has a viscosity that decreases under shear stress but stays constant over time is said to be pseudoplastic . A material that has a viscosity that decreases under shear stress and then continues to decrease with time is said to be thixotropic . If the transition from high viscosity (nearly semisolid) to low viscosity (essentially liquid) takes place only after the shear stress exceeds some minimum value, the material is said to be a bingham plastic .

Materials that thicken when worked or agitated are called shear-thickening fluids . An example that is often shown in science classrooms is a paste made of cornstarch and water (mixed in the correct proportions). The resulting bizarre goo behaves like a liquid when squeezed slowly and an elastic solid when squeezed rapidly. Ambitious science demonstrators have filled tanks with the stuff and then run across it. As long as they move quickly the surface acts like a block of solid rubber, but the instant they stop moving the paste behaves like a liquid and the demonstrator winds up taking a cornstarch bath. The shear-thickening behavior makes it a difficult bath to get out of. The harder you work to get out, the harder the material pulls you back in. The only way to escape it is to move slowly.

Materials that turn nearly solid under stress are more than just a curiosity. They're ideal candidates for body armor and protective sports padding. A bulletproof vest or a kneepad made of of shear-thickening material would be supple and yielding to the mild stresses of ordinary body motions, but would turn rock hard in response to the traumatic stress imposed by a weapon or a fall to the ground.

Shear-thickening fluids are are also divided into two groups: those with a time-dependent viscosity (memory materials) and those with a time-independent viscosity (non-memory materials). If the increase in viscosity increases over time, the material is said to be rheopectic . If the increase is roughly directly proportional to the shear stress and does not change over time, the material is said to be dilatant .

With a bit of adjustment, Newton's equation can be written as a power law that handles the pseudoplastics and the dilantants — the Ostwald-de Waele equation …

where η the viscosity is replaced with k the flow consistency index [Pa s n ] and the velocity gradient is raised to some power n called the flow behavior index [dimensionless]. The latter number varies with the class of fluid.

A different modification to Newton's equation is needed to handle Bingham plastics — the Bingham equation …

where σ y is the yield stress [Pa] and η pl is the plastic viscosity [Pa s]. The former number separates Bingham plastics from newtonian fluids.

Combining the Ostwald-de Waele power law with the Bingham yield stress gives us the more general Herschel-Bulkley equation …

where again, σ y is the yield stress [Pa], k is the flow consistency index [Pa s n ], and n is the flow behavior index [dimensionless].

viscoelasticity

When a force ( F ) is applied to an object, one of four things can happen.

F  =  ma

This term is not interesting to us right now. We've already discussed this kind of behavior in earlier chapters. Mass ( m ) is resistance to acceleration ( a ), which is the second derivative of position ( x ). Let's move on to something new.

F  = − bv

This is the simplified model where drag is directly proportional to speed ( v ), the first derivative of position ( x ). We used this in terminal velocity problems just because it gave differential equations that were easy to solve. We also used it in the damped harmonic oscillator, again because it gave differential equations that were easy to solve (relatively easy, anyway). The proportionality constant ( b ) is often called the damping factor.

F  = − kx

The proportionality constant ( k ) is the spring constant. Position ( x ) is not the part of any derivative nor is it raised to any power.

F  = − f

That symbol f makes it look like we're discussing static friction. In fluids (non-newtonian fluids, to be specific) a term like this is associated with yield stress. Position ( x ) is not involved in any way.

Put everything together and state acceleration and velocity as derivatives of position.

This differential equation summarizes the possible behaviors of an object. The interesting thing is that it mixes up the behaviors of fluids and solids. The more interesting thing is that there are occasions when both behaviors will be present in one thing. Materials that both flow like fluids and deform like solids are said to be viscoelastic — an obvious mash-up of viscosity and elasticity. The study of materials with fluid and solid properties is called rheology , which comes from the Greek verb ρέω ( reo ), to flow.

What old book gave me this idea? What should I write next?

Foods generally exhibit what is called viscoelastic behaviour, whereby a mix of the characteristic elastic properties of solids and flow properties of liquids are both found to varying extents

• Cheese pull occurs when melting fats lubricate linked protein strands. The fats flow like a liquid and the proteins stretch like a solid.

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Viscosity Science Experiments

How to Find the Volume of a Penny

Viscosity is the thickness of a liquid or its resistance to flow. Fluids with lower viscosity are referred to as thin liquids and those with higher viscosity as thick liquids. Friction between the molecules in a liquid causes viscosity. Basic viscosity experiments compare the viscosity of different liquids, the shape of the drops of liquids of different thicknesses and the effects of temperature and sugar on viscosity.

Compare Viscosity

Experiments to compare the relative viscosities of different liquids involve timing the fall of an object through a cylinder of the liquid. Use a long, glass cylinder with measurements clearly marked on its side. Place a small wad of cotton or other soft material on the inside at the bottom of the cylinder to protect it. Fill it with water to the top mark and drop a steel ball bearing into the liquid. Time how long the bearing takes to drop to the bottom of the container. Replace the water with liquids of different thicknesses, such as corn syrup or a mixture of glycerin and water, and repeat the experiment. Relate the time taken for the bearing to descend to the thickness or viscosity of the liquid.

Shape of Drops

A property related to a liquid's viscosity is the shape of the drops that it forms. The hypothesis is that liquids of higher viscosity form drops with longer "tails" than lower viscosity liquids. Collect a selection of liquids of differing viscosity and put each of them in turn into a pipette. Place a sheet of graph paper behind the pipette and squeeze the pipette bulb so that a drop of liquid emerges. Take a photo of the drop. Compare the photos and relate the shape of the drop to the viscosity of the liquid.

Effect of Temperature

Temperature affects the viscosity of a liquid. Drill a hole in the bottom of a metal measuring cup, cover it and add 1 cup of water at 20 degrees Fahrenheit. Uncover the hole and time how long it takes for the water to empty from the cup. Repeat this with water heated to 30, 40 and 50 degrees Fahrenheit and compare the findings. To extend this experiment, repeat the entire procedure with a different liquid, such as milk or corn syrup.

Adding Sugar

You can test liquids to see if the viscosity of a liquid changes with the addition of sugar. Dissolve 1 ounce of sugar into 1 cup of water and pour it into a metal cup with a hole in the bottom. Uncover the hole and record how long it takes for all of the liquid to leave the cup. Repeat this with mixtures of water and 2 ounces, 3 ounces and so on of sugar. Compare the results to find that the sugar increases the viscosity of the water and reduces its rate of flow.

Related Articles

Homemade clear liquid plastic, how to use a protractor to measure a triangle, how to calculate volume of a rectangular prism, how to find the area of a triangular prism, how to read a refractometer, how to calculate flow rate with pipe size and pressure, food coloring experiments, how to calculate viscosity, science projects: how hot & cold water changes a balloon, how to calibrate a refractometer, how to read a weather swan barometer, how to convert api gravity to density, how to make a galilean thermometer, how to make crystals with epsom salt, how to build a water clock, chemistry projects for diffusion in liquids, how to standardize a ph meter, water bottle science experiments, how to calculate the wavelength of sound.

• Stanford University; A Simple Viscosity Test; Giresh Gooray
• All Science Fair Projects; Does the Viscosity of Liquids Affect the Shape of Droplets Abstract Stephanie Rotan

About the Author

Christina Ash has been writing since 1982, throughout her career as a computer consultant, anthropologist and small-business owner. She has published work in various business, technology, academia and popular books and journals. Ash has degrees in computer science, anthropology and science and technology studies from universities in England, Canada and the United States.

Photo Credits

Ableimages/Photodisc/Getty Images

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Discover and compare the viscosity of different liquids, from oil to water.

The viscosity of a liquid is another term for the thickness of a liquid. Thick treacle-like liquids are viscous; runny liquids like water are less viscous.

This experiment should take 20 minutes. 

• Eye protection, if desired
• Sealed tubes of different liquids (thermometer packing tubes are ideal)

Choose from:

• Cooking oil
• Washing up liquid
• Shampoo or bubble bath

Health, safety and technical notes

• Read our standard health and safety guidance .
• Wear eye protection if desired.
• Ethanol is highly flammable, see CLEAPSS Hazcard HC040a .
• Take one of the tubes provided.
• Ensure the bubble is at the top and the tube is held vertical.
• Quickly invert the tube and measure the time it takes for the bubble to reach the top.
• Repeat this measurement for all the samples
• Complete a table, as shown below.

Remind students to time each liquid using a consistent method – eg measure the time from inversion until the ‘bubble first hits the top’. 

• Which liquid is the most viscous?
• Which liquid is the least viscous?
• Design a different experiment for comparing the viscosity of liquids.

Viscosity - teacher notes

Viscosity - student sheet, additional information.

This practical is part of our  Classic chemistry experiments  collection.

• 11-14 years
• 14-16 years
• 16-18 years
• Practical experiments
• Properties of matter

Specification

• Boiling points, melting points, viscosity and solubility/miscibility in water are properties of substances that are affected by hydrogen bonding.
• 2. Develop and use models to describe the nature of matter; demonstrate how they provide a simple way to to account for the conservation of mass, changes of state, physical change, chemical change, mixtures, and their separation.

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• Open access
• Published: 01 October 2020

Experimental measurements and modelling of viscosity and density of calcium and potassium chlorides ternary solutions

• Mohammad Arshad 1 ,
• Ahmed Easa 2 ,
• Hazim Qiblawey 1 ,
• Mustafa Nasser 3 ,
• Abdelbaki Benamor 3 ,
• Rahul Bhosale 1 &
• Mohammad Al-Ghouti 4  

Scientific Reports volume  10 , Article number:  16312 ( 2020 ) Cite this article

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Metrics details

• Chemical engineering

Measured viscosity and density data for ternary aqueous solutions of CaCl 2 and KCl are presented at temperatures between 293 and 323 K with 5 K increment. A modified Jones–Dole was introduced by adding extra terms and proved to be suitable for modelling of the viscosity data. Goldsack and Franchetto, Hu and Exponential models are used to correlate the viscosity data, too. Al models are correlated as a function of temperature and concentration. All models had successfully predicted the viscosity with high precision reaching a maximum average absolute deviation (AAD) of less than 2.3%. The modified Jones–Dole showed the best results among other models. Viscosity of the ternary solution is higher than the viscosity of water by about 15% at low concentrations and reaches about 270% at the highest concentrations. The amount of CaCl 2 has more significant effect on the ternary mixture viscosity compared to KCl. This has created difficulty in measuring the viscosity and consequently the challenge in finding the different models parameters. Ternary solution densities were successfully correlate with Kumar’s model with AAD of less than 0.4%. Comparison of the ternary solution density and viscosity with the few available data literature showed a good agreement.

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Unraveling the phase diagram-ion transport relationship in aqueous electrolyte solutions and correlating conductivity with concentration and temperature by semi-empirical modeling

Introduction.

Transport properties data of electrolyte solution is required for design and operation of many industrial processes like crystallization, food processing and fertilizer production. Dynamic viscosity is one of the important thermo-physical properties. The measurement of aqueous solution viscosity is expensive and time-consuming, especially when more than one electrolyte is involved. Theoretical and experimental investigations of viscosity of electrolyte aqueous mixture have been subject of interest to many researchers 1 , 2 , 3 , 4 , 5 .

Reaching clean water resources is becoming more difficult due to the increase of population, urbanization and climate changes. Nontraditional water resources are needed in order to cover the human’s need of water. In the past two decades, desalination technology was practiced and proved to be a sustainable solution to fill this gap 6 , 7 . In desalination, feed of saline water with high concentrations of electrolyte solutions are used to get the fresh water. Energy is needed to separate the salts from water to get the fresh water stream. In addition to the fresh water stream, another by-product stream is generated with substantially higher electrolytes concentration than the feed. This stream is called concentrate or brine stream. Seawater is usually the feed stream and the brine disposal is returned back to the sea 8 . Due to more strict environmental regulations in returning the brine stream back to the see, new technologies are required to mitigate this impact 9 . Fractional crystallization is among them, where the different salts in seawater including sodium chloride, potassium chloride, magnesium chloride and calcium chloride are crystallized as solid crystal and sold as high quality salts in the market. Brine streams are introduced to evaporators to increase the concentration of the salts to a level where crystallization takes place in the crystallizers. Depending on salts solubility, crystallization will take place. Therefore, NaCl will crystallize first leaving the brine concentrated with the rest of the other salts to leave to the next crystallization stage and so on 10 , 11 .

Concentrate disposal with high concentration of electrolyte content of both KCl and CaCl 2 among them is not only limited to desalination processes 12 . Other industries sharing this stream are mining processes such as oil and potash industries, salt dome for the storage of hydrocarbons and rejected brine from solar ponds used for heat generation 13 , 14 , 15 . In this work, the concentrated stream which contains both KCl and CaCl 2 will be investigated for its viscosity and density.

To calculate dimensionless quantities like Reynolds, Schmidt and Sherwood numbers, which they are relevant to engineering design applications, viscosity and density data are required. Therefore, both viscosity and density are closely related and are of importance to estimate the pumping cost, pipeline sizing and design of the evaporators and crystallizers in the brine recovery process 16 , 17 .

Viscosity and density data for CaCl 2  + KCl + H 2 O is available only at 298 K 18 . In this work, viscosity and density data for CaCl 2  + KCl + H 2 O at temperature from 293.15 to 323.15 K are presented. The data were correlated using three known models in the literature and one modified equation. Models are developed as function of both concentration and temperature since most of the related industrial processes are running under a medium- or low-pressure environment. To the best of our knowledge such data have not been reported in the literature before.

Experimental

The used chemicals in this work are listed in Table 1 . All chemicals were used without further purification. Procedure used in this work is similar to the one followed in the previous work 18 . Briefly, stock solutions were prepared by dissolving weighed amounts of CaCl 2 and KCl in double distilled water with a resistivity of 18.2 mΩ cm under continuous stirring. Viscosity and density are measured for ternary solutions prepared from the stock solutions by dilution. A precise analytical balance with an accuracy of 0.0001 g from Kern (ABS220-4) was used to prepare all the ternary solutions (gravimetric method). Ternary solutions were left under gentle stirring for a while to be sure that there is no crystal formation and they stay clear. Appearance of any crystals is a sign that the mixture is supersaturated and the sample was excluded because supersaturation was reached. This was considered as the maximum concentration in this study. In all samples, water was supplied from a Millipore water system. Each salt in the prepared ternary solutions were denoted as i = 1 for KCl, i = 2 for CaCl 2 and i = 3 for H 2 O.

Calibrated Ubbelhode viscometer with a capillary diameter of 0.00053 m (capillary type 0a) from SCHOTT was used to measure the kinematic viscosities. The viscometer has been further calibrated with double de-ionized water. The transit time of the liquid meniscus through the capillary of the viscometer using stopwatch was used to measure the kinematic viscosity of a given solution. The time was measured with a precision of ± 0.01 s. Each measurement was repeated five times to ensure reproducibility of the data. A maximum deviation of 0.4% was observed in the measurements. Viscosity was measured within a temperature range between 293.15 and 323.15 K, with increment of 5 K. The range of the studied molality was between 0.5 and 4 mol kg −1 . Densities of the solutions were measured precisely using an Anton Paar DMA 4500M density meter with an oscillating U-tube sensor. Double de-ionized water and toluene were used for calibration purposes. The uncertainty in temperature measurements is estimated to be 0.02 K (k = 1).

Solutions prepared for viscosity measurements were used to determine their densities. The density measurement accuracy was 0.00005 g cm −3 and repeatability was 0.00001 g cm −3 . Equation ( 1 ) was used to calculate the dynamic viscosity;

k represents the constant of the viscometer provided by the manufacturer and t is the flow time in seconds. The temperature was controlled with a thermostated water circulator. The precision was ± 0.01 K. The dynamic viscosity measurements had uncertainty of 0.003 mPa s.

Results and discussion

Experimental data, comparison of experimental data with published data.

As mentioned, viscosity and density data of this ternary system are only available at 298 K. Very few studies were found to have the same concentration in order to be compared with the current study. Zhang et al. 19 presented closer concentrations. It was found that deviations are reasonable. Maximum deviation was found to be 5.8% for viscosity at m 1  = 3.0 mol kg −1 and m 2  = 1.0 mol kg −1 , other viscosity data showed deviations around 1%. Density values are closer to the published data with a maximum deviation 0.49% as density is straightforward function of concentrations. Comparison of densities and viscosities is presented in Table 2 .

Discussion on experimental data

Densities and viscosities of the ternary aqueous solutions of KCl and CaCl 2 are presented in Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 at the investigated molalities between 0.5 and 4 mol kg −1 . Analyzing the density data, it was found that both solutes contributes positively to the density as expected. Analyze the effect of both separately reveals that CaCl 2 has more significant effect on the density of the mixture. For example, referring to Table 3 , increase in molality of KCl ( m 1 ) from 0.5 to 1.0 mol kg −1 increases the density by 1.9%. On the other hand, same increase in molality of CaCl 2 increases the density by 3.80%. However, variation in viscosity depends on the solute molalities (m 1 and m 2 ) and does not follow one trend. Jones–Dole equation defined below helps in understanding trend of viscosity of electrolytes aqueous solution.

where m is the ion concentration in mol kg −1 , η is the viscosity of the solution, and η 0 is the viscosity of pure solvent. A is Falkenhagen coefficient, which is determined by ion–ion interactions and may be calculated analytically by Debye–Hückel theory. The B-coefficient is related to the strength of ion–solvent interactions. Ions with positive B-coefficients are classified as kosmotropes (structure maker) and negative B-coefficients as chaotropes (structure breaker). A structure make ion (+ve B value) is supposed to increase the viscosity while structure breaker (−ve value of B) will decrease the viscosity.

In Fig.  1 , viscosity of ternary solution is plotted at fixed molalities of CaCl 2 . At low concentration of CaCl 2 (m 2  = 0.5–1.0 mol kg −1 ), viscosity of the ternary solution decreases initially with increasing molality of KCl reaching a minimum value, and then starts increasing monotonically. Viscosity data taken from literature 20 of binary solution of KCl (m 2  = 0 mol kg −1 ) is also shown on the same figure . As it can be observed that viscosity of the binary solution also decreases initially to a minimum at around m 1  = 1.5 mol kg −1 and then starts increasing. This trend is attributed to structure breaking property of K + (negative value of Jones Dole B coefficient) in binary solution reported by many researchers 20 , 21 , 22 , 23 , 24 , 25 . At lower concentration (up to 1.0 mol kg −1 ) of CaCl 2 , addition of KCl affects the viscosity in a similar manner as the binary KCl solution. Hence, it can be assumed that structure of the ternary solution at low concentration of CaCl 2 is close to that of the binary KCl solution. It is very clear from Fig.  1 that extent of structure breaking property of KCl is diminishing; lower negative slope in decreasing region and higher positive slope in increasing region of viscosity as concentration of CaCl 2 increasing from zero to 1.0 mol kg −1 . Figure  1 shows a presentation of the trend of viscosity decrease and increase to clarify the idea and not finding the slope for the data points. Moving to higher concentration of CaCl 2 , initial decrease in viscosity is not observed with increase in KCl molality as at higher concentration solute–solute interaction is supposed to dominate. Viscosity of ternary solution increases with increase in KCl concentration for CaCl 2 concentration (m 2 ) more than 1.5 mol kg −1 as shown in Fig.  1 .

Viscosity of ternary aqueous solution of KCl ( m 1 ) and CaCl 2 ( m 2 ) at 293.15 K. Solid line to show trend only.

Variation of viscosity with KCl concentration (m 1 ) at different temperatures is presented in Fig.  2 . It can be seen that a minima is observed at lower temperatures up to 308.15 K but after this temperature viscosity increased as concentration of KCl increases. At higher temperature, structure-breaking property of K + reduces as water structure is destroyed. Jones–Dole coefficient B values for KCl is found to be negative at lower temperatures and positive at higher temperatures as presented in Table 10 . Temperature dependent structure breaking property of KCl and other similar electrolyte has been reported in literature and discussed in details 18 .

Viscosity of ternary aqueous solution of KCl ( m 1 ) and constant CaCl 2 ( m 2 ) = 0.5 mol kg −1 at different temperatures .

In the previous work 18 , viscosity data of the ternary solutions of NaCl and CaCl 2 were correlated by three models available in the literature; the mixing model (GF model) developed by Goldsack and Franchetto 5 , 26 , the exponential model and the extended Jones–Dole model 27 . The present work, viscosity data of the ternary aqueous solution of potassium chloride and calcium chloride are correlated and predicted by the above mentioned models in addition to Hue equation 28 and modified extended Jones Dole.

Four models are presented in this work; two are purely predictive (GF model and Hue model). They use data of corresponding binary system and then predict the viscosity of ternary solution. While the exponential model is purely empirical as model coefficients are calculated by fitting the experimental data. The fourth model proposed in Eq. (5) can be called semi empirical as it used A–F values of binary system but G value is calculated by correlating with experimental data.

MATLAB non-linear fit tool NLINFIT was used to find the model coefficient of all models reported in this work. NLINFIT function least squares to estimate the coefficients of a nonlinear regression function. Viscosity is the dependent variable while m 1 and m 2 are the independent variables. Initial guesses of the coefficients as input are required. NLINFIT returns the predicted values of the viscosity along with the estimated coefficients. NLPREDCI and NLPARCI tools in MATLAB are used to calculate the confidence intervals for the predicted values.

Modified extended Jones Dole model

Zhangh et al. 19 extended the Jones Dole equation (Eq.  2 ) to be applicable for ternary solutions. The method calculates the viscosity of ternary solution by simple additive rules as shown in Eq. ( 3 ).

where m is the concentration in mol kg −1 , subscript 1 and 2 are for the corresponding binary solutions. A and B values were taken from 22 , 29 and the other coefficients of the model are calculated by fitting binary data to the corresponding equation for binary mixture as below.

In the previous work 18 , it has been shown that Eq. ( 3 ) failed to predict the corresponding viscosity of ternary solutions especially at higher concentrations. Calculated viscosity by Eq. ( 3 ) was found to be much smaller than the experimental viscosity of the ternary solution and at higher concentration deviation goes up to − 15% for the ternary system of CaCl 2 and NaCl. The discrepancy was due to the ions interaction at higher concentrations. In dilute solutions, enough water is available to hydrate all ions but in concentrated ones, the interaction of ions becomes stronger and hence real concentration of one electrolyte should be more due to the competition of the electrolyte ions for the available water molecules. Therefore, the reason behind the discrepancy of viscosity predictions using Eq. ( 3 ) could be due to the large differences between hydrating abilities of Ca 2+ and Na + /K + , strong repulsion between Ca 2+ and Na + /K + and greater difference of size and shape of Ca 2+ and Na + /K + ions 19 . So in order to minimize the deviations, an extra term (G) is introduced in Eq. ( 3 ), which can be called ions interaction parameter. Similar models with interaction coefficient are reported in literature for viscosity of liquids mixtures and Interaction coefficient is found to be temperature dependent only 30 . The modified equation can be expressed as below

Application of the calculation method proposed in Eq. ( 5 ) can be summarized in the following steps.

Getting A–F values in Eq. ( 4 ) for binary solutions: Jones–Dole coefficients A and B values for a particular binary solution can be obtained from literature to be used in Eq. ( 5 ). Using these values of A and B, viscosity data of binary solution can be regressed to Eq. ( 4 ) to obtain D–F values.

Getting term G: Once values of A–F are obtained for both binary solutions, these values are inserted in Eq. ( 5 ) and thus only the term G remains unknown. G can be obtained by regressing the viscosity data of ternary solutions against Eq. ( 5 ).

The above-mentioned methodology was applied to the measured data of ternary aqueous solution of KCl + CaCl 2 . KCl binary viscosity were taken from collection of data by Laliberté 31 . The values of coefficients A–D in Eq. ( 4 ) was good enough to correlate experimental viscosity data. Zhangh et al. 19 used Eq. ( 4 ) to correlate the viscosity of KCl binary solution, but after investigation, it was found that dropping the terms E and F affected the AAD % only by 0.1%. Therefore, the last two terms in Eq. ( 4 ) were dropped from the viscosity calculation. The coefficients were presented in Table 10 and AAD% of binary experimental viscosity data correlated to Eq. ( 4 ) was included in Table 10 , too. Equation ( 6 ) was used to calculate the average absolute deviation ( AAD );

where n is the number of data points.

For CaCl 2 binary data taken from 32 , coefficients A–F in Eq. ( 4 ) were required to correlate viscosity data accurately. The coefficients are presented in the Table 11 along with the AAD% of binary experimental viscosity data correlated to Eq. ( 4 ). The AAD% in both Tables 10 and 11 are less than 0.5%.

Calculated values of A–F for the two binary systems were inserted in Eq. ( 5 ), which was regressed against measured viscosity values of ternary system using least square method. Optimized values of parameter G were obtained and presented in Table 12 and Fig.  3 . Values of G was found to be decreasing with increase in temperature which means that interaction of ions is weakening at higher temperature.

Variation of term G in Eq. ( 5 ) for the ternary systems KCl + CaCl 2  + H 2 O, NaCl + MgCl 2  + H 2 O and NaCl + CaCl 2  + H 2 O against temperature.

Viscosity of ternary system of KCl + CaCl 2  + H 2 O calculated by Eq. ( 5 ) to be found in column 4 in all Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 . Experimental and calculated data were compared and the standard deviation ( SD ) was calculated using Eqs. ( 7 ).

p represents the number of adjusted parameters. Values of SD and AAD are reported at the bottom of Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 . SD values were found to be varying from 0.0124 to 0.0255. AAD% was found to be less than 1.0% with maximum deviation of around 2.0% at high concentrations of both solutes as shown in Fig.  4 . In Fig.  5 , experimental data of viscosity and viscosity predicted by Eq. ( 5 ) were presented. Analyzing statistical data along with Figs.  4 and 5 it can be concluded that with the introduction of interaction parameter G in Eq. ( 5 ) is predicting the viscosity data of ternary solution very well compared to Eq. ( 3 ).

Percentage deviation for the calculated viscosity of ternary system of KCl + CaCl 2  + H 2 O by different models for experimental data at 303.15 K.

Experimental data and correlated values of viscosity of ternary aqueous solution of KCl ( m 1 ) and CaCl 2 ( m 2 ) at 313.15 K. Solid lines are for Eq. ( 5 ) and dotted line are Hu model, Eq. ( 8 ).

The proposed model (Eq.  5 ) was also validated against another well-known binary system; NaCl + CaCl 2  + H 2 O based on the published data of the ternary system 18 . A–E coefficient for the binary NaCl solution were reported in Table 13 . A–B values were taken from Aleksandrov et al. 33 and D–E coefficient values were obtained by regression of Eq. ( 4 ) to the viscosity data taken from Kestin et al. 34 . After fitting viscosity data of ternary NaCl + CaCl 2  + H 2 O the value of the empirical parameters in Eq. ( 5 ) was obtained. Values of G along with Absolute average deviation (AAD) between experimental and predicted values by Eq. ( 5 ) were also presented in Table 13 and Fig.  3 . It can be concluded that Eq. ( 5 ) successfully predicted the viscosity of ternary solution of NaCl + CaCl 2  + H 2 O as AAD were less than 2% for all temperatures. G values for the ternary system NaCl + CaCl 2  + H 2 O were found to be higher than that of KCl + CaCl 2  + H 2 O suggesting stronger interaction for the former compared to the later.

Calculation method proposed in Eq. ( 5 ) was validated against published data 27 . Viscosity of ternary mixtures KCl + CaCl 2  + H 2 O and NaCl + CaCl 2  + H 2 O was calculated by Eq. ( 5 ) at the concentrations reported in the published data 27 by using A–F and G values presented in Tables 11 , 12 and 13 and compared with the measured reported data. Calculated and published measured viscosity are found to be very close with AAD equal to 0.85% for KCl + CaCl 2  + H 2 O system and 1.17% for NaCl + CaCl 2  + H 2 O. Maximum deviation of 3.9% and 3.2% was found for the systems KCl + CaCl 2  + H 2 O and NaCl + CaCl 2  + H 2 O respectively. This comparison is presented in Fig.  6 , which confirms that Eq. ( 5 ) is highly accurate in predicting the viscosity data already presented in the literature.

Comparison of calculated viscosity using Eq. ( 5 ) for ternary system of KCl + CaCl 2  + H 2 O and published viscosity data 19 at 298.15 K.

Equation ( 5 ) was also successfully applied to regress ternary viscosity mixture NaCl + MgCl 2 published data 3 . Ternary data for this system are only available in the range of temperature 298.15–318.15 K and hence G values for these temperatures are reported in Table 12 along with AAD for experimental data and values obtained by Eq. ( 5 ).

So, the overall method proposed in Eq. ( 5 ) was validated for viscosity of three ternary systems; KCl + CaCl 2  + H 2 O, NaCl + CaCl 2  + H 2 O, and NaCl + CaCl 2  + H 2 O. G Coefficient, which is a measure of the overall deviation arising in additive methods of calculating viscosity of ternary solution (Eq.  3 ), is plotted against temperature in Fig.  3 . Ion interaction Coefficient G is found to be decreasing with temperature for all systems. To investigate further the G dependency on temperature, the following model is used to correlate it with temperature.

Optimized value of model coefficients of Eq. ( 8 ) are found to be; A = 5.04E−05, B = 1182.78, C = 110.90 for KCl + CaCl 2  + H2O, A = 0.00208, B = 254.06, C = 219.54 for NaCl + CaCl 2  + H 2 O and A = 0.003571, B = 249.02, C = 213.20. Therefore, it is clear that temperature dependence of G coefficients for all three systems follows the same trend (see Fig.  3 ). At a fixed temperature, different values of G for different ternary system suggest that it is governed by properties of cations present in that system. These properties of cations include the cation hydration extent, difference of shape and size, and repulsive forces. More ternary system should be investigated to find out which of the above factor(s) is/are significant in controlling the ion coefficient parameter.

Hu equation

Hu and Lee 35 has proposed simple predictive equation for viscosity of mixed electrolyte solution based on the absolute rate theory 36 and the equation of Patwardhan and Kumar 37 . Hu equation can be expressed as

where \(\eta_{i}^{o}\) is the viscosity of \(i\) binary solution having the same ionic strength as that of mixed solution, \(x_{i}^{o}\) is the mole fraction of \(i\) in binary solution( \(i\) -H 2 O) having the same ionic strength as that of mixed solution, \(x_{i}\) is the mole fraction of \(i\) in the binary solution ( \(i\) -H 2 O).

Measured values of ternary aqueous solution viscosity of KCl + CaCl 2 were used to test Eq. ( 9 ). The procedure is briefly summarized as follows 38 :

Fit the available data 19 , 32 of measured viscosity for binary solution by the following equations:

where \(\eta_{i}^{o}\) and \(m_{i}^{o}\) represent the viscosity and the molality of the binary aqueous solution. The optimum fit was obtained by varying \(A_{i}\) s until the values of \(\partial_{\eta ,i}\) is less than 10–4. \(\partial_{\eta ,i}\) is calculated according to Eq. ( 11 ).

The values of \(A_{i}\) obtained for binary solutions are shown in the Table 14 .

Determine the composition \({{m}_{i}}^{o}\) of the binary solutions with the same ionic strength as that of ternary solution of given molalities \(m_{i} (i = 1,2).\)

Compare predicted and measured data.

Comparison between experimental viscosity and predicted one were made by calculating average absolute deviation (AAD%) and standard deviation (SD) and reported in Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 . Maximum AAD and SD was found to be 1.31% and 0.0199 m Pa s respectively. Experimental data and calculated viscosity were plotted in Fig.  5 . The deviations in Fig.  4 suggest that Hue equation predicts the viscosity of ternary solution reasonably accurate.

Exponential model

Many researcher 27 , 39 , 40 , 41 have used the following semi-empirical exponential model and successfully correlated the model with the viscosity of sodium and calcium solution and sodium and magnesium solution at high concentrations of salts 18 .

where a , b 1 , b 2 , f 1 and f 2 are the model coefficients. In this work, Eq. ( 12 ) was correlated to the data presented in Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 at all studied temperatures.

The coefficients; b 1 , b 2 , f 1 and f 2 in Eq. ( 12 ) were found to be temperature independent and have constant values, but the coefficient a was found to be temperature dependent. The optimized values of b 1 , f 1 , b 2 and f 2 are 0.0302 ± 0.0055, − 0.0005 ± 0.0019, 0.2726 ± 0.0040 and 0.0132 ± 0.0018, respectively. Temperature dependence of parameter a in Eq. ( 12 ) was modeled by Eq. ( 13 ). Coefficient a values at different temperatures are presented in Table 15 .

where a 0 , a 1 and a 2 are adjustable parameters. The calculated values for the ternary KCl + CaCl 2  + H 2 O are 0.0302 ± 0.012, 557.1013 ± 138.7 and 132.9 ± 21.5 for a 0 , a 1 and a 2 respectively. Consequently, the final temperature dependent viscosity model can be expressed as follows.

Viscosity of the ternary solution calculated by Eq. ( 14 ) was compared with the measured viscosity of KCl + CaCl 2  + H 2 O in this work. The maximum value of AAD was found to be 1.63% at the temperature of 293.15 K, otherwise it is less. Percentage deviation plot as depicted in Fig.  4 against all the concentrations at the temperature of 303.15 K (as an example) suggest that maximum deviation was 1.87%. These statistical data above leads to the conclusion that Eq. ( 13 ) fits well the experimental data.

Goldsack and Frachetto model (GF model).

Many researcher has adapted a model based on absolute rate theory derived by Goldsack and Frachetto 23 to predict the viscosity of electrolyte mixtures 42 , 43 . The equation is as follows:

X 1 and X 2 are the mole fractions presented in the following two equations for a solution made of two electrolyte 1 and 2, while E and V are dimensionless free energy and volume parameters, subscript 1 and 2 are for the corresponding binary solutions.

Values of \(\nu {}_{1}\) and \(\nu_{2}\) are 2 and 3 respectively while E and V parameters of corresponding binary solution can be calculated by regressing the binary viscosity data against corresponding Goldsack and Frachetto viscosity model for binary solution as expressed in Eq. ( 18 ):

Electrolytes with a total of two ions (1:1 electrolyte) like NaCl, KCl and MgSO 4 , mole fraction of cations is calculated as:

Electrolytes with a total of three ions (1:2 electrolyte) like CaCl 2 , MgCl 2 and Ca(NO 3 ) 2 , mole fraction of cations can be calculated as:

Equations ( 15 ) to ( 20 ) were used to predict the viscosity of the ternary solutions of potassium and calcium chlorides.

Regressing the binary data for KCl 23 to Eqs. ( 18 ) and ( 19 ), E and V values were calculated and reported in Table 16 . E 2 and V 2 values that correspond for CaCl 2 binary data were taken from the work 18 . The calculated values were inserted into Eqs. ( 14 ) to ( 16 ) in order to predict the viscosity of ternary mixtures. Validity of GF model against KCl + CaCl 2  + H 2 O viscosity data was investigated by calculating AAD. Maximum AAD was found to be 2.3% at 318.15 K. A representative plot for percentage deviation between the measured and the calculated viscosities was shown in Fig.  4 . It suggests that at two points, deviation crosses 3.0% (3.7% and 3.3%) otherwise it is around 1.0% at other points.

Density modelling

Kumar 44 , 45 , 46 proposed a simple method to predict the density of ternary solution, which can be expressed as follow

where y j is the ionic strength fraction of the j th salt and can be written as

where M is the molecular weight and d is the density. The subscript j is salt in the electrolyte solution and d o is density of water.

Equation ( 21 ) was used to predict the density of ternary solution at the molarities investigated in this work. Calculation method for Eq. ( 20 ) are available in the literature 44 , 45 . Density values calculated by Eq. ( 21 ) at all studied temperature are presented in Tables 3 , 4 , 5 , 6 , 7 , 8 and 9 . AAD and SD were also calculated and found to be s ranging from 0.12 to 0.40 and from 0.0018 to 0.0056 g cm −3 respectively. Experimental density and density predicted by Eq. ( 21 ) was plotted in Fig.  7 . Figure  7 and statistical calculations advocate that Eq. ( 21 ) proposed by Kumar is accurate enough to predict the density of the ternary solution for the concentrations and temperatures range used in this study. This is true for the NaCl + CaCl 2  + H 2 O system as well 18 .

Plot of predicted values versus experimental data of density of ternary aqueous solution of KCl + CaCl 2  + H 2 O at 323.15 K.

Conclusions

Viscosity and density data for aqueous ternary system are still of interest for our industrial daily life applications. The measured data were compared with the available published data. The models used in this work were able to predict well the viscosity as function of both concentration and temperature and density of the specific system KCl + CaCl 2  + H 2 O studied in this work. The Calculation method proposed in this work (Eq.  5 ) has been compared to other investigated ternary aqueous solutions investigated in previous published work 18 ; NaCl + CaCl 2  + H 2 O and NaCl + MgCl 2  + H 2 O and reached the same conclusion.

The performance of the four models used in this work along with a representative plot of percentage deviations for all models is presented in Fig.  4 . The exponential model is showing the least deviation because it is purely empirical and depends only on quality experimental ternary data. AAD for Hu model is also very low, although it is a predictive model because this model uses the empirically calculated A’s coefficients of a polynomial fitted to binary data. On the other hand, G-F model is showing little higher deviations than other models, as it is predictive model and depends on how accurately E and V values are calculated by fitting binary data to an equation based on absolute rate theory. Overall, performance of the model proposed in Eq. ( 5 ) is excellent. This model has the special characteristic of being associated with very fundamental Jones–Dole viscosity model. It is highly recommended to be used and validated for other ternary systems.

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M.A. experimental data analysis and modelling part and contributed to the final manuscript. A.E. carried out the experiments. H.Q. conceived the original idea, supervised the project and contributed to the final manuscript. M.N. and A.B. have contributed to density measurement. R.B. and M.A. have contributed to the interpretation of the results and contributed to the final manuscript.

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Correspondence to Hazim Qiblawey .

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Arshad, M., Easa, A., Qiblawey, H. et al. Experimental measurements and modelling of viscosity and density of calcium and potassium chlorides ternary solutions. Sci Rep 10 , 16312 (2020). https://doi.org/10.1038/s41598-020-73484-4

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Published : 01 October 2020

DOI : https://doi.org/10.1038/s41598-020-73484-4

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Science Experiments

Viscosity of Liquids Science Experiment

Viscosity? If you’ve never heard this word before you might think it’s a new brand of kitchen cleaner! But of course, if it’s not a kitchen cleaner, what in the world is it?

We’ll help define viscosity in our easy to understand explanation of how it works below, but the goal of this experiment is to help kids ‘see’ viscosity in action.

Collect your materials, print out our detailed instructions, and watch our demonstration video to explore how the consistency of a liquid impacts objects.

JUMP TO SECTION: Instructions | Video Tutorial | How it Works

Supplies Needed

• 4 clear glass jars of the same size (we used pint-sized mason jars)
• Water (enough to fill one jar)
• Corn Syrup (enough to fill one jar)
• Cooking Oil (enough to fill one jar) We used Vegetable Oil, but any Cooking Oil will work.
• Honey (enough to fill one jar)

Viscosity of Liquids Science Lab Kit – Only $5

Use our easy Viscosity of Liquids Science Lab Kit to grab your students’ attention without the stress of planning!

It’s everything you need to  make science easy for teachers and fun for students  — using inexpensive materials you probably already have in your storage closet!

Viscosity of Liquids Science Experiment Instructions

Step 1 – Gather four clear glass jars and fill one with water, one with corn syrup, one with cooking oil (we used vegetable oil, but any cooking oil will work) and one with honey.

As you are pouring the liquids, take a moment to make observations. What do you notice as you pour the water into the glass? What about the corn syrup, the cooking oil and the honey? Did you notice anything different?

Do you think the liquid will impact what happens when a marble is placed into each jar? What do you think will happen? Write down your hypothesis (prediction) and then continue the experiment to test it out and to find out if you were correct.

Step 2 – Carefully drop one marble into each jar. Drop one marble at a time and observe what happens to the marble when it enters the liquid. You’ll notice right away that the marble behaves differently in each jar. Was your hypothesis correct? Do you know why some marbles sink to the bottom of the jar quickly and some marbles sink to the bottle of the jar slowly?

Find out the answer in the how does this experiment work section below. It also contains ideas on how you can expand on the experiment.

Viscosity of Liquids Science Experiment Video Tutorial

How Does the Science Experiment Work?

The question answered in this experiment is: how does the consistency of a liquid impact how long it will take for a marble to sink in a jar of that liquid? A unique property of liquids is something called viscosity.

Viscosity is a liquid’s resistance to flowing.

Viscosity depends on the size and shape of the particles that make the liquid, as well as the attraction between the particles. Liquids that have a LOW viscosity flow quickly (ie. water, rubbing alcohol, and vegetable oil). Liquids that have a HIGH viscosity flow slowly (ie. honey, corn syrup, and molasses). Viscosity can also be thought of as a measure of how “thick” a liquid is. The more viscous (or thick) a liquid is, the longer it will take for an object to move through the liquid.

In our experiment, the marbles took longer to sink when dropped into the jars filled with corn syrup and honey than they did when dropped into the jars filled with water and cooking oil. Therefore, we’ve shown that corn syrup and honey have a higher viscosity (or are more viscous) than water and cooking oil.

More Science Fun

• How long will it take? Expand on the experiment, by estimating how long it will take for the marble to sink to the bottom of the jar? Then set a timer and find out how close your estimate was. Tip: Timing the marble, works best when using liquids that have a high viscosity (ie. honey, corn syrup, and molasses).
• The Pouring Test – When you are finished dropping the marbles into the jars, try pouring the liquids one at a time into another jar. You will notice that it takes longer to pour out the Corn Syrup and Honey than it does to pour out the Water and Cooking Oil. This is because the viscosity of a liquid can also be observed by how slow (or fast) it takes to pour the liquid.
• How Does the Consistency of a Liquid Impact Magnetic Attraction – This experiment shows how the viscosity of a liquid impacts how fast (or slow) the objects move toward a magnet.

I hope you enjoyed the experiment. Here are some printable instructions:

Viscosity of a Liquid Experiment Science Experiment

• 4 clear glass jars of the same size (we used pint sized mason jars)
• Cooking Oil (enough to fill one jar)

Instructions

• Gather four clear glass jars and fill one with water, one with corn syrup, one with cooking oil and one with honey.
• Carefully drop one marble into each jar. Drop one marble at a time and observe what happens to the marble when it enters the liquid. Which marbles sink to the bottom of the jar quickly and which marbles sink to the bottle of the jar slowly.

Reader Interactions

December 13, 2017 at 5:00 pm

The honey and corn syrup has a higher density than the water and oil because ther are more particals in a certain amount of space making it slower for the marball to sink to the bottom.

April 28, 2019 at 1:51 pm

Some liquids are less dense. Some liquids are more dense. The denser liquids make the marbles flow slower. The less dense liquids (water and oil) make the marbles flow faster. The more dense liquids (honey and corn syrup) make the marbles flow slower.

September 17, 2019 at 7:37 am

Viscosity is a measure of a fluid’s resistance to flow. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion…… So it is to do with the size and shape of the molecule rather than the density. If you heat up a liquid the density will change slightly but the viscosity will change a lot.

August 22, 2020 at 12:33 am

Honey is much thicker than oil, so the process is a little slower than the marble goes to the bottom of the honey.

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FREE K-12 standards-aligned STEM

curriculum for educators everywhere!

Find more at TeachEngineering.org .

• TeachEngineering
• Measuring Viscosity

Hands-on Activity Measuring Viscosity

Grade Level: 9 (8-10)

Time Required: 1 hours 15 minutes

Expendable Cost/Group: US $1.00

Group Size: 3

Activity Dependency: Viscous Fluids

Subject Areas: Algebra, Biology, Chemistry, Measurement, Physical Science, Physics, Reasoning and Proof

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Engineers often design devices that transport fluids, use fluids for lubrication, or operate in environments that contain fluids. Thus, engineers must understand how fluids behave under various conditions. Understanding fluid behavior can help engineers to select the optimal fluids to operate in devices or to design devices that are able to successfully operate in environments that contain fluids.

After this activity, students should be able to:

• Measure the viscosity of a fluid.
• Describe a fluid as having "high" or "low" viscosity.

Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .

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Each group needs:

• graduated cylinder (the taller the better)
• marble or steel ball (must be half the diameter of the cylinder or smaller, and sink in the fluid being measured; the slower the ball sinks, the easier it is to measure the viscosity)
• Viscosity Activity Worksheet , one per person
• calculators
• Internet access, to research viscosities for one worksheet question

To share with the entire class:

• thick, somewhat clear household fluids, such as motor oil, corn syrup, pancake syrup, shampoo, liquid soap (perhaps a different fluid for each 1-2 groups), enough of each liquid to fill a graduated cylinder for each group that tests it
• scale, to measure the masses of graduated cylinders, with and without the liquids

Fluid mechanics is the study of how fluids react to forces. Fluid mechanics includes hydrodynamics, the study of force on liquids, and aerodynamics, the study of bodies moving through air. This encompasses a wide variety of applications. Can you think of any examples of engineering applications for which an understanding the behavior of fluids is important? (Listen to student ideas.) Environmental engineers use fluid mechanics to study pollution dispersion, forest fires, volcano behavior, weather patterns to aid in long-term weather forecasting, and oceanography. Mechanical engineers implement fluid mechanics when designing sports equipment such as golf balls, footballs, baseballs, road bikes and swimming gear. Bioengineers study medical conditions such as blood flow through an aneurysm. Aerospace engineers study gas turbines that launch space shuttles and civil engineers use fluid mechanics for dam design. Considering just these few examples of the wide variety of applications of fluid mechanics, you can see how fluid mechanics is important to understand for many types of engineering design in our world.

In this activity, we'll be measuring a property of fluids called viscosity. Viscosity describes how a fluid resists forces, or more specifically shear forces . Shear is the type of force that occurs when two objects slide parallel to one another. Since fluids are composed of many molecules that are all moving, these molecules exert a shear force on one another. Fluids with low viscosity have a low resistance to shear forces, and therefore the molecules flow quickly and are easy to move through. Can anyone name an example of a low-viscosity fluid? (Listen to student ideas.) One example is air! Another example is water. Fluids with high viscosity flow more slowly and are harder to move through. What are examples of high-viscosity fluids? (Listen to student ideas). One example of a high-viscosity fluid is honey.

Being able to re-arrange equations to find the unknowns is an important skill for engineers! In this activity, we will measure the viscosities of a few household fluids by dropping balls into them and measuring the terminal velocities.

Before the Activity

• Gather materials and make copies of the Viscosity Activity Worksheet .
• Be sure the ball sinks slowly enough in all of the fluids that a velocity measurement can be obtained. If the ball falls too quickly, it is hard to accurately start and stop the stopwatch.
• Divide the class into groups of three students each. Hand out the worksheets.

With the Students

• Have each group choose a fluid to measure the viscosity of (or assign each group a fluid).
• Have students calculate the density of the fluid.
• Weigh the empty graduated cylinder.
• Fill the cylinder with fluid, and record the volume.
• Weigh the full graduated cylinder. Subtract the mass of the empty graduated cylinder to determine the mass of the fluid.

Note: 1 cm 3 =1 ml.

• Have students measure the density of the sphere.
• Measure the radius of the ball. Record as r [cm].

Alternatively, place the sphere in a graduated cylinder half filled with water; the displacement of the water is equal to the volume of the sphere.

• Have students drop the ball into the fluid, timing the ball as it falls a measured distance.

(Note: Ideally students would wait for the ball to reach a constant velocity, however for this activity we assume the ball reaches terminal velocity very quickly, so that students can measure the time from when the ball enters the fluid until it reaches the cylinder bottom. For less-viscous, "thinner," fluids, this may be very quick).

where g is acceleration due to gravity (981 [cm/s 2 ]). The answer should be in units of kg/cm s, or mPa-s. For comparison, the viscosity of water is approximately 1 mPa-s.

• For accuracy, have students repeat the experiment and calculate an average viscosity.
• Have groups share, compare and discuss their results as a class by either writing the results in a table on the board or on a class overhead projector.

shear: A type of force that occurs when two objects slide parallel to one another.

terminal velocity: The point at which the force exerted by gravity on a falling object is equaled by a fluid's resistance to that force.

viscosity: A fluid's ability to resist forces.

Pre-Activity Assessment

Discussion Questions: Considering the fluids available for activity testing, ask students to estimate which liquid they think will have the highest viscosity. Which will have the lowest? Write their predictions on the board.

Activity Embedded Assessment

Worksheet : Have students complete the Viscosity Activity Worksheet during the activity. If time is limited, have them research online for viscosities of common household fluids (last question) as a homework assignment. Review their answers to gauge their comprehension of the subject matter.

Post-Activity Assessment

Graphing: Have students plot fluid density (independent) vs. viscosity (dependent). In addition, students could compare marbles of various diameters and describe patterns between fluid density and viscosity, and between fluid density and marble diamater. Students then determine if the model is linear, quadratic, or exponential; if linear, use the two-point method to determine the line of best fit.

Class Presentation: Have students share and discuss their measured/calculated viscosities with the class. Compare and discuss the class results with the predictions made before beginning the activity.

Safety Issues

• Do not allow students to drink the test fluids, especially after the fluids have been in contact with the graduated cylinders.
• After the activity, responsibly dispose of the used test fluids.
• Shampoo or dish soap may create a large amount of suds when cleaning the graduated cylinders.

If the marble falls too quickly through the fluid to obtain accurate timing, use a taller graduated cylinder or a lighter marble (or both!).

Viscosity changes with temperature! Have students measure the viscosity of a fluid at a few different temperatures and graph the viscosity (y-axis) vs. temperature (x-axis).

• For lower grades, just visually compare the times it takes the balls to fall through the fluids. Perhaps a viscosity race!
• For upper grades, try varying the temperature of a fluid (see the Activity Extension section).

tudents are introduced to the similarities and differences in the behaviors of elastic solids and viscous fluids. In addition, fluid material properties such as viscosity are introduced, along with the methods that engineers use to determine those physical properties.

Students are introduced to Pascal's law, Archimedes' principle and Bernoulli's principle. Fundamental definitions, equations, practice problems and engineering applications are supplied.

Students learn why engineers must understand tissue mechanics in order to design devices that will be implanted or used inside bodies, to study pathologies of tissues and how this alters tissue function, and to design prosthetics. Students learn about collagen, elastin and proteoglycans and their ro...

Contributors

Supporting program, acknowledgements.

The contents of these digital library curricula were developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

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Effects of temperature on viscosity of oil

Introduction: (initial observation).

Viscosity is one of the important physical properties of many fluid products. Consumers often care about the consistency of products that they buy. Any variation in the viscosity of a product from time to time can be an indication of unreliability of a product. For lubricants, motor oils, and cooking oils the viscosity is also sensitive to the temperature and varies in different temperatures. This can cause some other problems. For example, if you use a motor oil that becomes very viscose in cold weather, you will have trouble in starting the engine in winters. The effect of temperature on viscosity has been the subject of research by universities and manufacturers of lubricant oils for many years and has lead to the development of additives and materials that can control the viscosity of oil in different temperatures. The problem is that there are so many different oils and so many different applications. That is why research on viscosity and proposing solution is always a money making task for many consultant engineers. Such studies need to be done case by case and every case is different from others. In this project you will explore the effect of temperature on viscosity of an oil sample.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “ Ask Question ” button on the top of this page to send me a message.

If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.  

Project advisor

Also please visit Interactive Viscosity test Experiment while gathering information.

Information Gathering:

Some of the challenges in doing this science project are: _ How can we test the viscosity? _ What oils can be used for our tests? First think!

How would you measure the viscosity of an oil? Can you come up with your own method of testing, comparing, or measuring viscosity?

After thinking for a while, it is time to do some research. Search the net for “Measuring viscosity”, “Viscosity unit”, “viscosity defined” and “viscosity test”.

Notice that in this project you don’t need (or you don’t have) to measure the viscosity. You just need to compare it. However it is good if you also learn about measurement of viscosity and do some experiments about it.

Read me for more info…

Viscosity is a measurement of the flow properties of a product. In order to understand what viscosity is, you need to realize that it is the ratio of the shear force applied and the amount of resulting deformation. The deformation of the fluid is expressed as the rate of shear . Therefore, viscosity is the relationship between shearing stress and rate of shear.

In the simplest cases, like water or aqueous solutions, the shearing stress is directly proportional to the rate of shear. The proportionality constant is called the viscosity coefficient or the viscosity of the liquid. Fluids where the proportion is direct are called Newtonian .

The unit of measurement is the poise , which is dyne.sec.cm-2. Normal viscosities are expressed as centipoise, where 100 centipoise =1 poise.

So what does this all mean from a product developer’s perspective? Well if it’s a food or a beverage you’re developing, it means you need to consider the impact of the viscosity on the product itself and also on the processing of it.

Fluids, including finished beverages, are either Newtonian or Non-Newtonian. The simplest are the Newtonian ones, like water, dilute suspensions, aqueous solutions, and emulsions. The following are some common products and their viscosities.

Notice that viscosity is temperature dependent and typically decreases as the temperature rises.

Viscometers are of several types. The most often seen in food and beverage development are based on rotational viscometry; meaning they measure viscosity by sensing torque required to rotate a spindle at a constant speed while immersed in the fluid. The torque is proportional to the viscous drag on the spindle, and thus to the viscosity of the fluid.

The probe pictured above is used to measure viscosity. With the attachments shown to the left, this probe can be inserted into a flowing liquid while the gauge at the top, shown on the right-hand side of the probe, reads the fluid’s viscosity.

There are many ways to measure viscosity, including:

• attaching a torque wrench to a paddle and twisting it in a fluid.
• using a spring to push a rod into a fluid.
• seeing how fast a fluid pours through a hole.
• Seeing how fast a liquid pours through a funnel.
• Seeing how long it takes for a bubble to come up.

In our experiment we will use one of the oldest and easiest ways: we will simply see how fast a sphere falls through a fluid. The faster the sphere falls, the lower the viscosity. This makes sense: if the fluid has a high viscosity it strongly resists flow, so the sphere falls slowly. If the fluid has a low viscosity, it offers less resistance to flow, so the ball falls faster.

To compare the viscosity of different liquids or the viscosity of one liquid at different temperatures we can simply compare the falling time. However we can also go one step further and actually measure the viscosity.

The measurement involves determining the velocity of the falling sphere. This is accomplished by dropping each sphere through a measured distance of fluid and measuring how long it takes to traverse the distance. Thus, you know distance and time, so you also know velocity, which is distance/time.

The formula for determining the viscosity is impressive, decorated with Greek letters and a squared term, but simply amounts to multiplying some numbers and then dividing by some others:

delta p = difference in density between the sphere and the liquid in g/cm3

g = acceleration of gravity = 980 Cm/s2

a = radius of sphere (in Centimeters)

v = average velocity = d/t = (distance sphere falls in Centimeters)/(time it takes to fall in seconds) = Cm/s

The resulting Viscosity will be in g/Cm.s or Poise

This equation makes sense in that spheres that fall slowly have low velocities. This makes the denominator small, so the answer (viscosity) is large. Viscosity is measured in units of Pa s (Pascal seconds), which is a unit of pressure times a unit of time. This is not especially intuitive. How does it relate to flowing liquids? One way of looking at it is to realize that pressure is force per square area. This makes a little more sense: force applied to the fluid, acting for some length of time.

[ Note : our experiment uses kilograms, meters, and seconds, rather than grams, centimeters, and seconds. Viscosity can be measured in g-cm-s, with the resulting unit called the poise; 10 poise = 1 Pa s. You may prefer those units to kg-m-s because densities are the more familiar grams per cubic centimeters.]

The measurement should be repeated many times to arrive at a good average value, and, most important, to observe the scatter in the results. This allows an assessment of the uncertainty in the measurement. Using spheres of different radii and densities and measuring the viscosities of at least two liquids gives a good idea of this unusual physical property and the power of an equation to predict behavior.

If you want to calculate the viscosity, you will need to know some densities. You can calculate the densities yourself or find them, however the following are some densities that you might need.

Here are the viscosities of some other common substances:

100 Centipoise = 1 Poise 1 Centipoise = 1 mPa s (Millipascal Second) 1 Poise = 0.1 Pa s (Pascal Second) Centipoise = Centistoke x Density

Question/ Purpose:

The purpose of this project is to know the effects of temperature on viscosity of the oil.

Identify Variables:

The temperature is an independent variable. ( the one that we set or modify )

The viscosity of the oil is the dependent variable. ( It changes by changes in temperature )

Experiment Design:

In order to compare or measure the viscosity, we will drop a glass marble or a steel ball bearing in the oil and measure the time that it gets to the bottom. We will then modify the temperature of the oil and repeat the test again. We will record our observation data (falling time) in a table and analyze it to see the effect of temperature on viscosity. The following procedures include calculations for measurement of viscosity. If you just want to compare viscosities, simply skip the calculations and only include time in your tables. Also the following experiment assumes that you want to repeat each test 10 times and get the average. You may choose to do it less or more.

Your final results table may look like this:

You may go to higher temperatures as well. Just remember heated oil gets much hotter than boiling water and it is very dangerous. I recommend not to try temperatures over 100º C. You may use a meat thermometer or other types of kitchen thermometers or laboratory thermometers for measuring the temperature.

If you do measure all viscosities as described in the next experiment, enter the results in a table like this:

Experiment 1:

This experiment is to measure the viscosity of one oil at one temperature. We drop a ball and measure the time. Then use the drop time to calculate the viscosity.

Procedure : 1.Choose the spheres and the oil to use for this activity. Enter the data for these materials into the Viscosity “Data Table.” If necessary, measure the radius of the sphere (hint: it is easier to measure the diameter and divide by two).

2.Determine the density of a sphere by measuring its mass and calculating its volume [remember that volume = (4/3) pr3]. Enter the value in the data table.

3.Enter the density of the liquid you are using (about 920 kg/m3 for oils, 1000 for shampoos) in the data table as “Fluid density.”

4.Fill a cylinder with a liquid, up to about 5 cm from the top.

5.Mark with tape a convenient starting point about 2 cm below the surface of the liquid (which will allow the sphere to reach terminal velocity before you begin making measurements). You can use either the top or the bottom of the tape, but use the same points for each measurement you make when you drop the spheres (step 8). 6.Mark an ending point about 5 cm from the bottom.

7.Measure the distance between the starting and ending points, and enter the answer in the data table as “Fall distance.”

8.You need an assistant to hold a sphere just touching the liquid while you get ready to measure the time of fall with a stop watch. The timer says “Go,” and his or her assistant drops the ball. The timer begins timing when the ball crosses the start line and ends it when it crosses the end line. You can use either the top or the bottom of the tape, but use the same points you used for the distance measurement.

9.Enter the data into the data table.

10.When you have made all 10 measurements, calculate the velocity at which the ball fell from this equation: velocity = distance/time. Enter the velocity values into the data table.

11.Now calculate the viscosity from this equation:

delta p = difference in density between the sphere and the liquid

g = acceleration of gravity

a = radius of sphere

v = velocity

12.Average your results for each experiment.

Viscosity Data Table

v = velocity = d/t = (distance sphere falls)/(time of it takes to fall)

Materials and Equipment:

• Oil for test (How about olive oil?)
• Spheres of different densities
• graduated cylinders or other long tubes
• meter stick
• Viscosity “Data Table”
• Viscosity “Histogram”

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

If you do any calculations, write your calculations in this section of your report.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

Sample list of references/ bibliography.

http://www.pdlab.com/visc.htm

Engine oil and its viscosity

Massey, B S (1983) Mechanics of Fluids, fifth edition, ISBN 0442305524

Download free Viscosity- und Rheology E-book in English and German:

Introduction to Rheology by Gebhard Schramm in English language ( http://www.haake.de/info/Rheology_GSchr_E.pdf )

Einführung in die Rheologie von Gebhard Schramm in deutscher Sprache ( http://www.haake.de/info/Rheology_GSchr_D.pdf )

It is always important for students, parents and teachers to know a good source for science related equipment and supplies they need for their science activities. Please note that many online stores for science supplies are managed by MiniScience.

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Independent and Dependent Variables Examples

The independent and dependent variables are key to any scientific experiment, but how do you tell them apart? Here are the definitions of independent and dependent variables, examples of each type, and tips for telling them apart and graphing them.

Independent Variable

The independent variable is the factor the researcher changes or controls in an experiment. It is called independent because it does not depend on any other variable. The independent variable may be called the “controlled variable” because it is the one that is changed or controlled. This is different from the “ control variable ,” which is variable that is held constant so it won’t influence the outcome of the experiment.

Dependent Variable

The dependent variable is the factor that changes in response to the independent variable. It is the variable that you measure in an experiment. The dependent variable may be called the “responding variable.”

Examples of Independent and Dependent Variables

Here are several examples of independent and dependent variables in experiments:

• In a study to determine whether how long a student sleeps affects test scores, the independent variable is the length of time spent sleeping while the dependent variable is the test score.
• You want to know which brand of fertilizer is best for your plants. The brand of fertilizer is the independent variable. The health of the plants (height, amount and size of flowers and fruit, color) is the dependent variable.
• You want to compare brands of paper towels, to see which holds the most liquid. The independent variable is the brand of paper towel. The dependent variable is the volume of liquid absorbed by the paper towel.
• You suspect the amount of television a person watches is related to their age. Age is the independent variable. How many minutes or hours of television a person watches is the dependent variable.
• You think rising sea temperatures might affect the amount of algae in the water. The water temperature is the independent variable. The mass of algae is the dependent variable.
• In an experiment to determine how far people can see into the infrared part of the spectrum, the wavelength of light is the independent variable and whether the light is observed is the dependent variable.
• If you want to know whether caffeine affects your appetite, the presence/absence or amount of caffeine is the independent variable. Appetite is the dependent variable.
• You want to know which brand of microwave popcorn pops the best. The brand of popcorn is the independent variable. The number of popped kernels is the dependent variable. Of course, you could also measure the number of unpopped kernels instead.
• You want to determine whether a chemical is essential for rat nutrition, so you design an experiment. The presence/absence of the chemical is the independent variable. The health of the rat (whether it lives and reproduces) is the dependent variable. A follow-up experiment might determine how much of the chemical is needed. Here, the amount of chemical is the independent variable and the rat health is the dependent variable.

How to Tell the Independent and Dependent Variable Apart

If you’re having trouble identifying the independent and dependent variable, here are a few ways to tell them apart. First, remember the dependent variable depends on the independent variable. It helps to write out the variables as an if-then or cause-and-effect sentence that shows the independent variable causes an effect on the dependent variable. If you mix up the variables, the sentence won’t make sense. Example : The amount of eat (independent variable) affects how much you weigh (dependent variable).

This makes sense, but if you write the sentence the other way, you can tell it’s incorrect: Example : How much you weigh affects how much you eat. (Well, it could make sense, but you can see it’s an entirely different experiment.) If-then statements also work: Example : If you change the color of light (independent variable), then it affects plant growth (dependent variable). Switching the variables makes no sense: Example : If plant growth rate changes, then it affects the color of light. Sometimes you don’t control either variable, like when you gather data to see if there is a relationship between two factors. This can make identifying the variables a bit trickier, but establishing a logical cause and effect relationship helps: Example : If you increase age (independent variable), then average salary increases (dependent variable). If you switch them, the statement doesn’t make sense: Example : If you increase salary, then age increases.

How to Graph Independent and Dependent Variables

Plot or graph independent and dependent variables using the standard method. The independent variable is the x-axis, while the dependent variable is the y-axis. Remember the acronym DRY MIX to keep the variables straight: D = Dependent variable R = Responding variable/ Y = Graph on the y-axis or vertical axis M = Manipulated variable I = Independent variable X = Graph on the x-axis or horizontal axis

• Babbie, Earl R. (2009). The Practice of Social Research (12th ed.) Wadsworth Publishing. ISBN 0-495-59841-0.
• di Francia, G. Toraldo (1981). The Investigation of the Physical World . Cambridge University Press. ISBN 978-0-521-29925-1.
• Gauch, Hugh G. Jr. (2003). Scientific Method in Practice . Cambridge University Press. ISBN 978-0-521-01708-4.
• Popper, Karl R. (2003). Conjectures and Refutations: The Growth of Scientific Knowledge . Routledge. ISBN 0-415-28594-1.

Viscosity of Newtonian and non-Newtonian Fluids

Successful characterization of viscosity is key in determining if a fluid is Newtonian or non-Newtonian

VISCOSITY OF NEWTONIAN AND NON-NEWTONIAN FLUIDS

If you are on this site, you probably have a general idea about what is viscosity and how important it is in the development of any application that involves fluid flow. However, fluid characterization is far more deep and complex than what is usually expected. Each unique material has its own behavior when subjected to flow, deformation or stress. 

Depending on their viscosity behavior as a function of shear rate, stress, deformation history..., fluids are characterized as Newtonian or non-Newtonian.

Newtonian Fluids

Newtonian fluids are named after Sir Issac Newton (1642 - 1726) who described the flow behavior of fluids with a simple linear relation between shear stress [mPa] and shear rate [1/s]. This relationship is now known as Newton's Law of Viscosity, where the proportionality constant η is the viscosity [ mPa-s ] of the fluid:

Some examples of Newtonian fluids include water, organic solvents, and honey. For those fluids viscosity is only dependent on temperature. As a result, if we look at a plot of shear stress versus shear rate (See Figure 1) we can see a linear increase in stress with increasing shear rates, where the slope is given by the viscosity of the fluid. This means that the viscosity of Newtonian fluids will remain a constant (see Figure 2) no matter how fast they are forced to flow through a pipe or channel (i.e. viscosity is independent of the rate of shear). 

An exception to the rule is Bingham plastics, which are fluids that require a minimum stress to be applied before they flow. These are strictly non-Newtonian, but once the flow starts they behave essentially as Newtonian fluids (i.e. shear stress is linear with shear rate). A great example of this kind of behavior is mayonnaise. 

Newtonian fluids are normally comprised of small isotropic (symmetric in shape and properties) molecules that are not oriented by flow. However, it is also possible to have Newtonian behavior with large anisotropic molecules. For example, low concentration  protein or polymer solutions might display a constant viscosity regardless of shear rate. It is also possible for some samples to display Newtonian behavior at low shear rates with a plateau known as the zero shear viscosity region.  

Non-Newtonian Fluids

In reality   most fluids are non-Newtonian, which means that their viscosity is dependent on shear rate   (Shear Thinning or Thickening) or the deformation history (Thixotropic fluids). In contrast to Newtonian fluids, non-Newtonian fluids display either a non-linear relation between shear stress and shear rate (see Figure 1), have a yield stress, or   viscosity that is dependent on time or deformation history   (or a combination of all the above!).

A fluid is shear thickening if the viscosity of the fluid increases as the shear rate increases (see Figure 2). A common example of shear thickening fluids is a mixture of cornstarch and water. You have probably seen examples of this on TV or the internet, where people can run over this kind of solutions and yet, they will sink if they stand still.  Fluids are shear thinning if the viscosity decreases as the shear rate increases. Shear thinning fluids, also known as pseudo-plastics, are ubiquitous in industrial and biological processes. Common examples include ketchup, paints and blood. 

Non-Newtonian behavior of fluids can be caused by several factors, all of them related to structural reorganization of the fluid molecules due to flow. In polymer melts and solutions, it is the alignment of the highly anisotropic chains what results in a decreased viscosity. In colloids, it is the segregation of the different phases in the flow that causes a shear thinning behavior. 

Why Should I Care?

Fluid flow is highly dependent on the viscosity of fluids. At the same time for a non-Newtonian fluid, the viscosity is determined by the flow characteristics . Looking at Figure 3, you can observe three very different velocity profiles depending on the fluid behavior. For all these fluids, the shear rate at the walls (i.e. the slope of the velocity profile near the wall) is going to determine viscosity. Successful characterization of viscosity is key in determining if a fluid is Newtonian or non-Newtonian, and what range of shear rates needs to be considered for an specific application.  Many viscometers on the market measure index viscosity but often lack proper characterization of shear rate and absolute or true viscosity.  Absolute viscosity is one of the most important parameters in the development and modeling of applications that involve fluid flow. Therefore, proper characterization of viscosity must be carried out at a shear rate that is relevant to the specific process.   Learn more about RheoSense viscometers and how they allow measurements of true viscosity over a wide range of shear rates. 

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The viscosity of honey – experiment.

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The viscosity of honey ranges from runny to almost solid. In this experiment, you can compare the viscosity of several types of honey.

To compare the viscosity of different types of honey.

Honey, viscosity.

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August 27, 2015

Marble Race--in Liquid!

A kitchen science project by Science Buddies

By Science Buddies

Syrup or honey? Oil or water? Who will win in this liquid, marble-race challenge? Test the viscosity of common liquids around your house, and find out!

George Retseck

Key concepts Physics Friction Solids Liquids

Introduction Have you ever tried to squeeze honey or syrup out of a bottle at breakfast on a chilly winter morning? Do you notice that it's harder to do that than on a hot summer day? As the liquid gets colder, its viscosity, or resistance to flow, increases. Viscosity is a properly of liquids that can be very important in very different applications—from how the syrup flows out of your bottle to how blood flows through the human body to how lava flows out of a volcano. In this project you will learn a little bit about viscosity by holding a marble race!

Background You experience friction all around you. It is what allows your shoes to grip the floor so you don't slip and it's what makes your bike come to a stop when you squeeze the brakes. This type of friction is a force that resists motion between two solid objects. Liquids, however, have friction, too—not just against solids (for example, water against a drinking glass)—but also internal friction, the liquid against itself. This internal friction is called viscosity. Different liquids have different viscosities, which means some liquids flow more easily than others. You will notice this if you think about squirting water out of a bottle or squirt gun. Imagine how much harder that would be to do with cold syrup!

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There are several different ways scientists can measure the viscosity of a liquid. One method is called a "falling sphere viscometer," in which you drop a sphere (such as a marble) through a tube filled with liquid. By measuring how long it takes the marble to fall and how far it travels, you can figure out the liquid’s viscosity. You won't need to do any calculations in this activity—but you will get to "race" marbles by dropping them in different liquids. Will viscosity affect how fast the marbles fall? Try this project to find out!

About a dozen equal-size marbles

At least two equal-size tall, transparent drinking glasses (the taller the better)

Assorted liquids from around your kitchen you have permission to use, such as water, syrup, honey, molasses, olive oil, vegetable oil, etcetera

Strainer or colander

A flat surface that can have liquids (water, oil, etcetera) spilled on it—or protection (such as a large trash bag) for the surface

Optional: Extra bowls/containers and/or a funnel (for storing and reusing the liquids you use for the activity, if you do not want to throw them away)

Optional: Volunteer to help you see which marble hits the bottom first

Preparation

If you want to save and reuse the liquids you use from the activity, make sure you thoroughly wash your marbles and drinking glasses with soap and water, then dry them completely. This will assure they are clean and you do not get your liquids dirty.

Prepare a work space on your flat surface and ensure that it is ready for any accidental spills (of water, oil, etcetera).

Fill your two (or more) drinking glasses with each of your different liquids to the same height. (To avoid spilling when you drop the marbles in do not fill them all the way to the brim.)

Which liquid do you think has a higher viscosity? Can you tell when you pour them into the glasses? Do you think the marble will fall faster through one of the liquids?

Hold one marble in each hand, just above the surface of the liquid in each glass.

Watch the glasses closely. Be prepared to watch the bottom to see which marble hits first. If you have a volunteer, have them look at the glasses, too.

Let the marbles go at exactly the same time.

Observe which marble hits the bottom of the glass first.

Which marble won the "race"? Do your results match your prediction?

Repeat the activity with a few more marbles to see if you get the same results. (Use clean, dry marbles each time.)

If you have more than two different liquids, you can try racing marbles in other liquids to see what happens.

Through which liquid do the marbles fall the fastest? The slowest?

Extra: What happens if you drop different types of marbles (for example, steel marbles versus glass marbles) or different size marbles? Do the results of your races change?

Extra : What happens if you change the temperature of a liquid? Have an adult help you cool some syrup in the refrigerator and heat some on the stove or in the microwave. What happens if you do a race with cold versus warm syrup instead of room-temperature syrup? How does temperature affect the liquid’s viscosity? Is the temperature effect stronger on some liquids than it is for others?

[break] Observations and results When pouring your liquids, you might have noticed that some of them were "thicker" or harder to pour. These are the more viscous liquids. You can also think about what these liquids are like when you use them everyday. For example, what would happen if you poured water on pancakes? Would it flow slowly like syrup or spread out very quickly? What about if you tried to pour and drink a glass of syrup? Taste (and healthfulness) aside, would that be harder than drinking a glass of water?

You should have observed that the marbles fell more slowly through more viscous liquids (such as syrup) than through less viscous liquids (such as water). This is because the more viscous liquids have more resistance to flow, making it more difficult for the marble to travel through them. It might be hard to tell the difference between the results for some liquids, however—especially if your glasses are not very tall. This is why it is important to do multiple trials and have a volunteer help watch the marbles.

Cleanup If you want to keep the remaining liquids for future use, have an adult help you pour them back into storage containers. (Use the strainer to remove the marbles). Otherwise, have an adult help you dispose of the liquids properly. Be careful because pouring some viscous liquids (such as cooking oil) down the sink can clog the drain.

More to explore Race Your Marbles to Discover a Liquid's Viscosity , from Science Buddies What Is Viscosity? , from Princeton University It's a Solid… It's a Liquid… It's Oobleck! , from Scientific American Science Activities for All Ages! , from Science Buddies

This activity brought to you in partnership with Science Buddies

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Viscosity Experiment With Marbles

Learn about the viscosity of fluids with a simple viscosity experiment. Grab some marbles and determine which will fall to the bottom first. We love  science experiments  that are fun and easy to do!

What Is Viscosity?

Friction is a force that is created when there is motion between two solid objects. Liquids can also have friction. This internal friction is called viscosity .

All liquids have different viscosities, which means some liquids flow more easily than others. Viscosity is a physical property of fluids. The word viscous comes from the Latin word viscum, meaning sticky. It describes how fluids resist flow or how “thick” or “thin” they are.

Viscosity is affected by what the fluid is made of and the temperature of it. For example, water has a low viscosity, as it is “thin.” Hair gel is much more viscous than oil and significantly more than water!

Learn about the viscosity of fluids by having a marble race. Try this fun marble drop experiment below! You could even turn it into an easy viscosity science project.

• Clear glasses
• Various liquids (water, syrup, honey, oil)
• Ruler (optional)
• Printable Instructions (see below)

Instructions:

STEP 1: Fill your glasses with your various liquids. Make sure they are all filled to the same level.

Learn more about using the scientific method for kids.

STEP 2: Place your ruler on top of your glasses and then place the marbles on top.

STEP 3: Tip your ruler toward you to release all of the marbles into your glasses at the exact same time.

STEP 4: Watch closely to see which marble reaches the bottom of the glass first. Did you guess which marble would win?

Using The Scientific Method

The scientific method is a process or method of research. A problem is identified, information about the problem is gathered, a hypothesis or question is formulated from the information, and the hypothesis is tested with an experiment to prove or disprove its validity.

Sounds heavy… What in the world does that mean?!? It means you don’t need to try and solve the world’s biggest science questions! The scientific method is all about studying and learning things right around you.

As children develop practices that involve creating, gathering data evaluating, analyzing, and communicating, they can apply these critical thinking skills to any situation.

LEARN MORE HERE: Using The Scientific Method with Kids

Note: The use of the best Science and Engineering Practices is also relevant to the topic of using the scientific method. Read more here and see if it fits your science planning needs.

Helpful Science Resources

Here are a few resources that will help you introduce science more effectively to your kiddos or students. Then you can feel confident yourself when presenting materials. You’ll find helpful free printables throughout.

• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• 8 Science Books for Kids
• All About Scientists
• Science Supplies List
• Science Tools for Kids
• Join us in the Club

FREE printable viscosity science project!

More Fun Viscosity Experiments To Try

Kids can use common household materials to try more viscosity experiments!

1. Cornstarch and Water: Oobleck!

Mix cornstarch with water in a bowl until you get a gooey substance. Have the kids try to stir the mixture slowly and then quickly. Discuss how the mixture behaves differently at different speeds, demonstrating its non-Newtonian properties.

2. Honey and Syrup Races

Fill two identical containers with honey and syrup. Have the kids tip the containers simultaneously, observe, and discuss which one flows faster. This demonstrates the different viscosities of honey and syrup.

3. Oil and Water Exploration

Fill a transparent container with water and drop some cooking oil into it. Observe how the oil forms droplets and floats on the water due to its lower viscosity. Discuss why the oil and water don’t mix.

Extend this viscosity experiment with alka seltzer tables. See lava lamp experiment.

4. Bubble Fun with Dish Soap

Mix dish soap with water to create a bubble solution. Use different amounts of soap to create solutions with varying viscosities. Have the kids blow bubbles and observe how the size and stability of the bubbles change with different soap concentrations.

Check out more bubble science experiments kids will love!

5. Ketchup vs. Mustard Race

Fill two squeeze bottles, one with ketchup and the other with mustard. Have the kids squeeze both bottles onto a plate and observe and discuss which condiment has a higher viscosity.

6. Molasses Pouring

Pour molasses or honey onto a plate and observe its slow flow. Discuss how molasses has a higher viscosity compared to water.

7. Dropper Races

Fill two droppers with liquids of different viscosities, such as water and honey. Challenge the kids to squeeze the droppers and observe how fast the liquids come out. Discuss the differences in flow rate.

8. Hot and Cold Syrup

Heat one container of syrup and keep another at room temperature. Compare the viscosity of the warm and cold syrup by pouring them onto a plate. Discuss how temperature can affect viscosity.

More Fun Science Experiments

• Magic Milk Experiment
• Self Inflating Balloon Experiment
• Egg in Vinegar Experiment
• Mentos and Coke Experiment
• Pop Rocks Viscosity Experiment
• Water Density Experiment

Printable Science Projects For Kids

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