water candle and glass experiment

Getting the facts right

Besides pedagogy or psychology, it can be also relevant just to get the facts right. The Water-Candle experiment is an illustrative example. It is a situation where many different effects play together and where it is hard to figure out, which ones really matter. My own perspective about this experiment has shifted several times and comments of some who wrote me added valuable insight. Please look also towards the end of this page, where some interesting links are added and information like why the great Lavoisier himself replaced this experiment as it appeared to be too subtle.

Cover a burning candle with a pitcher so that the candle is in an air-tight room sealed by the water at the ground.

After some time, the candle dims and goes out. Just before the candle dies, the water level rises to almost 1/10 th of pitcher height. No air bubbles are seen. The water level stays up for many few minutes more.

: oxygen O and C H react. The burning produces water H O and carbon dioxide C O . For n=1, we balance the equation as follows: + C H = C O + 2 H O

There are two different effects. Both a chemical and a physical reasoning are needed to explain what we can see. Both and matter. The initial cancellation effect can confuse the observer. plays a role when the chemical equations are balanced.

Photos of the experiment

An exhibit of explanations

What do we learn, appendix: the chemical equation for general n.

O + x C H = y C O + z H O

(1+3 n) O + 2 C H = 2 n C O + (2+2n) H O

Appendix: the ideal gas equation

p V = N k T

Added March 20, 2011

Added September 26, 2011

What is happening in this experiment? When we ignite the candle, the hydrocarbon reacts with oxygen (in excess) to produce carbon dioxide and water. The burning sets an air current which gives dome shape to candle flame and it helps to get complete combustion at the bottom and the outer surface of the flame. The hot air and products of combustion rise up above the flame. As soon as the gas jar comes over the flame, the hot gases moving upward enter the jar and air inside the jar expands pushing some of the air out of the jar. This process goes unnoticed. As soon as the jar touches the water, the burning occurs in a closed environment. Further pressing the jar into water helps to retain the air in jar which is less in quantity than at room temperature and pressure. However, due to thermal expansion, the pressure is higher than atmospheric pressure which is balanced by pressure from the water. The burning of hydrocarbon in the jar produces about 30% more molecules of carbon dioxide and water than the molecules of oxygen consumed in the reaction (see below the title expected chemical reaction). The increased heat and number of molecules increases the pressure in side as a result if not careful some bubbles of gas will escape from the jar. Over the time the oxygen in the jar is reduced and conditions for burning are changed. Burning under reduced oxygen may not produce carbon dioxide rather carbon monoxide (very little). When the candle is put out, the temperature decreases followed by also a decrease in pressure due to condensation of water vapour and decreased quantity of air due to thermal expansion during the process of placing the jar on the candle. The overall situation is a decrease in pressure inside the jar as compared to atmospheric pressure. Therefore, despite water is heavier that air, it is pulled into the jar. How much water rises as a result of dissolving of carbon dioxide? Very little practically negligible during 30 - 40 minutes, the time the experiment usually takes for performing in a classroom situation. If the number of candles is increased in the jar, the heat produced is more therefore more air is likely to escape from the jar due to thermal expansion during the process of pacing the jar over them. Therefore, more water will rise in the jar with more candles. The nature and quantity of the products will depend upon the composition of candle material. However, it is assumed that combustion of saturated hydrocarbons is taking place during burning. C H (s) + (1.5n+0.5) O (g) = n CO (g) + (n+1) H O(g) For n=1, two moles of oxygen reacts with a mole of CH to produce three moles of product molecules. Assuming that supply of methane was controlled and it is stopped as soon as the flame is put out, otherwise there will be an explosion. The number of moles of the product molecules is 1.50 times that of oxygen. As n increases, the multiple factor decreases from 1.50 and approaches 1.0 at n = ? For n=30 (a typical paraffin wax), the factor will be 1.34. The overall understanding of the experiment is that all the oxygen is not used up (I have rested the presence of oxygen after the candle is put out in our laboratory using yellow phosphorus) and the consumption of oxygen does not create empty space rather the number of product molecules in the jar increases over that of the consumed oxygen. Thus giving rise to an increase in overall pressure in the jar (see above equation). Moreover, almost equal number of molecules of CO and H2 are produced. A quick rise of water in the jar after the candle is extinguished is mainly due to a decrease in pressure as a result of a decrease in amount of air in the jar due to thermal expansion during the process of placing the jar on the candles, bubbles escaping (if any) through the water and may be the condensation of the water vapour. The amount of condensation of water will depend upon the temperature difference between initial and final temperature of the air in the jar. Since air is above water, therefore saturated water vapour pressure is considered in the beginning of the experiment. Increase in temperature, during the candle burning, will make air unsaturated to accommodate additional water vapours especially produced as a product of burning. A decrease in temperature over time after the candle is off to the initial temperature will help water vapour to condense. This condensation will decrease the pressure inside the jar and will help water rise in the jar. The amount of water vapours condensed during a small change of temperature as usually occurs in this experiment may even be small to notice. The amount of CO dissolved in water is minimal in the 30-40 minutes during which experiment is conducted.

Added November 20, 2011

: theoretically, if you assume that the candles will burn up all the oxygen in the container, and assume the room is completely air tight and assume that both water and air incompressible, it does not matter. You will have the same water level at the end in both setups after the candles have burned out and the situation cooled down.

In real experiments, there are differences but they depend on the actual experiment:

Added January 23, 2012

Simo Tolvanan from Helsinki kindly informed me about the . explains things very well and also contains much history and references. This paper makes the story again interesting. It points to the fascinating story of Lavoisier, who first realized that the total does not change during this process and who noticed that only a fraction of the oxygen reacts before the candle goes out by demonstrating that a mouse still can breath afterwards. The authors of the article provide also The classical is compatible what is seen by everybody else and which matches the . The experiments demonstrate only a one percent increase. The authors conclude that bubbling and hot air trapping are responsible for the rising water. The setup for and the experiments are very different. In the later case, the candle burning is violent and the container is very long. Heavier CO (which the ignition already produces in the first moments) can kill the candle before much of the oxygen is out.

January 27 2012: the bubbling effect. Here is an illustration why many teachers report bubbles. If you place the pitcher flat on then bubbles escape initially. One can avoid this by tilting the glass first. We just want initially to have the same level of water and the same pressure inside and outside. The experiment starts then.
Candle experiment done carefully so that initially the water level inside is close to the water level outside.	Bubbles which escape.

Added February 5, 2013

had a great idea to modify the experiment. He wrote: The stoichiometry for coal is different than for paraffin. In the case of only carbon, one has and one would indeed expect that the volume would stay the same. Since the pressure decreases afterwards, this could indicate that indeed some air has gone out when the heat has expanded the inside. After cooling, the plastic wrap collapses.

Peter Dureen again: I think this is more indication that some hot air has left the container before it started to cool down. I have repeated the experiments also with different type of containers and seen also some air, as other teachers have observed too. Faraday had been a fantastic experimenter and assisted as a chemist before for a long time. Lavoisier was definitely a great pioneer in this context.

Added January 21, 2014

sent the following interesting thoughts: . What do you think of this? This is a pretty good simplification. It defuses well the myth that the oxygen is burned away. The reason why the myth persists because the rise of water matches the amount of oxygen in the air. again: O produced in burning the candle wick was wet and hard to relight. Thus I decided that there was no way that Lavoisier could have learned much from this particular experiment. So I managed to locate . Note that he abandons the candle and water experiment as having potential flaws. He moves to mercury instead, and lights the candle after the jar is in place. What he ends up on is this: "In the middle of a glass stand, was placed a small wax candle; and on the top of the wick was fixed a small piece of Kunckel's phosphorus. The stand was then placed in a basin of mercury and covered with a jar. I made a piece of iron wire red hot then passed it through the mercury set fire to the little piece of phosphorous and by this means the candle was lighted." What he found was that the heated air initially pushed the mercury down, but when everything had cooled, there was a tiny loss in the volume of air, 1/300th the volume. But then he reacted the air with a CO absorber and the volume was reduced by 1/10. In other words he claims that the total volume was virtually unchanged, but (assuming air is 1/5 oxygen) about 1/2 the oxygen was converted into CO (with an unspecified amount turned into water. He may not have realized water was a byproduct yet). The combustion of paraffin is C H + 38 O => 25 CO + 26 H O. Depending on what fraction of the water remains as vapor, one goes from 38n moles to between 25n and 51n moles of CO +H O of vapor (with the rest in condensed H2O). Now it could be by chance that the C O+H O vapor happened to be near 38n, but that would be just chance. In your opinion, what fraction of the H O condenses? This should depend on the temperature and the humidity already present in the room. If we believe the account of Lavoisier, it could indeed be that things pretty much balances out when done as described. This makes the experiment so interesting. There are various effects which play a role: physical like temporary heating and cooling as well as condensation as well as chemical due to the reaction of paraffin with stochiometric computations which depending on the type of paraffin is used. The experiment depends on the size of the container, the surrounding temperature, air humidity present as well as on the experimenter (lightening the candle, allowing air to escape initially for example through bubbles or due to the expansion while removing the lightener).

Added March 30, 2021

My answer:

Added January 28, 2024

My answer:

Posted on Last updated: December 8, 2021 By: Author Kim

Categories STEM Activities

Rising Water Experiment – Magic Water Science Experiment

Rising Water Experiment: a magic rising water science experiment.

Ages: Preschool , PreK , Kindergarten, Elementary
Difficulty: Easy
Learning: STEM , Air Pressure, Ideal Gas Law, Charles’s Law

Did you know you can make water rise without touching it?

Nope, it isn’t magic. It’s science. Surprisingly simple science in fact. This science experiment comes together in minutes, but it will captivate your children.

Here is how to do the raising water experiment, simple glass and candle STEM magic.

Text: Rising Water Experiment Science for Kids. Picture: Shallow dish with blue water, upside down glass with water rising into it

What's In This Post?

Supplies for your Glass and Candle Experiment

How to do the rising water experiment, the science, the chemical component, the physical component, the big picture, what should children take away from this science experiment, conservation of matter, charles’s law, ideal gas law, ask a question, magic water science experiment, free printable raising water experiment instructions, instructions, rising water experiment.

This experiment uses at-home materials and is fascinating! It does require adult help, but adults will love it too.

You only need a few items to make this magic water STEM experiment work. Here is what you need to gather up:

Glass or Jar
Small Votive Candle
Shallow Dish
Food Coloring (Optional)
Matches or Lighter

Before we even get started please remember that an adult needs to be present for this experiment. We are using fire, which can be dangerous, so be smart.

Step 1: Take a sallow dish and fill it with water. You want just enough to cover the bottom.

Step 2: If you want, add food coloring to the water. This just makes it easier to see and is fun, so totally optional.

Step 3: Place your small votive in the middle of the dish.

Step 4: Light the candle, then quickly place the empty glass over the flame, touching the water. Now wait while the candle burns out.

Step 5: Watch as the water rises up into the glass!

Left picture: shallow dish with blue water. Lit candle in center of dish with glass upside down on top. Right picture: candle has burnt out and water level within glass has risen up

The number one safety tip here is to be careful with the flame! This experiment must be done with adult supervision at the bare minimum. With younger children, like preschoolers, this needs to be an adult-led experiment.

This STEM activity also uses glass, so it is a good idea to be careful in case it falls or breaks.

Clean-up for this activity is pretty simple. Slowly lift the bottle off of the candle.

Once the bottle is off, gently blow the candle out. Let the candle cool (or have an adult get it), remove it from the dish, and dump the water down the drain. That’s it!

More must do activities!

Text: Easy and Fun Fireworks Experiment Science for Kids. Top Picture: Star cookie cutter with fireworks reaction bubbling up with glitter. Bottom Picture: Butterfly and star cookie cutters in a dish with fireworks baking soda and vinegar experiment with glitter bursting up

How the Rising Water Experiment Works

This is a pretty cool experiment, but it is important to talk about what actually makes this happen. It’s fun to say it is magic, but as my kids tell me, ‘It’s better. It’s science.’

There are two main components of this experiment that cause the water to rise, a physical component and a chemical component. These two components work together to make this experiment happen.

The candle burning creates a chemical reaction. The flame burns both the paraffin (candle wax) and the oxygen under the glass. This reaction uses up oxygen and creates water and carbon dioxide as a result. Twice as much oxygen is burned than carbon dioxide produced, so the volume of air in the glass decreases.

(Note the total amount of matter in the jar remains the same. Conservation of matter tells us this. But some molecules are larger than others and take up more space in terms of volume.)

Picture of general chemical reaction of burning a fuel. Fuel + oxygen yields carbon dioxide and water. Reaction is general and unbalanced, components are labeled

The physical component is why the water level in the glass doesn’t rise as soon as the candle is covered. The candle warms the air, and this increases the air volume inside the glass.

When the candle burns out (because all the oxygen is used up), the temperature cools quickly. This temperature decrease means the volume also decreases, which lets the water rise to fill up that space. This is called Charles’s Law.

Charles’s Law tells us that the ratio of volume to temperature must remain the same, so if one goes down the other goes down too.

Charles's Law. Picture of Charles's law equation of Volume 1 over Temperature 1 equaling Volume 2 over Temperature 2. V=Volume T=Temperature

These two parts of the experiment work together. Both the volume change and temperature also affect the pressure in the system we created. When temperature decreases (the physical component) and the size of the matter decreases (the chemical component), the pressure of the gas inside the glass decreases too.

This lower pressure inside means the water can rise as well. This is explained by the Ideal Gas Law.

The idea of air pressure can be a bit challenging for young children to understand. It isn’t something they can clearly see, so that makes sense. But they can understand something changing size, in other words when volume changes.

If the air inside the glass takes up less space, it makes sense for the water to fill in that space and rise inside the glass.

Ideal Gas Law Equation. PV=nRT. V=Volume, T=Temperature, n=Moles, P=Pressure, R=Ideal Gas Law Constant

I understand that we went over a lot of more complicated concepts here. (And don’t worry, I’ve listed the definitions for the terms below to help out.) Am I really expecting young kids to understand and retain all this?

No. I mean, it would be cool if they did. And some might. But realistically that is not the point of this kind of science. The purpose of giving these explanations is so that you as a caregiver can quickly get the reasoning behind this project and interpret it for your children.

It is helpful for your children to see these experiments. Even if they don’t fully understand the details, this experience is adding to their understanding of how the world around them works. It builds their science base.

Using the vocabulary helps kids as well. First, it gives new words which are always helpful for communication skills. But I think, more importantly, it demystifies science later in life. Science can feel like a whole new language as we get older, and that can be very intimidating. If we have been exposed to these terms though, it’s less scary. We might not know exactly what they mean but we know that we have heard them before. This helps kids feel like science belongs to them. Because it does.

Text: Rising Water Experiment Science for Kids. Top Picture: shallow dish with blue water, candle in the middle with empty glass upside down on top. Bottom picture: candle has burned out and water level in the glass has gone up

Helpful Definitions

Here are a few helpful definitions for the raising water experiment.

The conservation of matter law states that matter is not destroyed or created. It can change forms, but the total amount stays the same.

Charles’s Law tells us that the volume of a gas is directly proportional to the temperature of the gas. As the volume decreases, the temperature decreases, for example.

The Ideal Gas Law describes the conditions a gas is under and how those conditions will vary as compared to each other. The pressure of the gas multiplied by the volume will always equal the number of moles multiplied by the temperature and ideal gas law constant.

The Scientific Method

Since an adult is needed to run do this experiment with kids (fire safety!), it is a great time to talk through the scientific method! Here is a guideline of what that can look like with this STEM experiment.

(And don’t forget to learn all the life lessons that come along with the scientific method here: Beyond the Science- What Kids Are Really Learning .)

Ask your child, what do they think is going to happen when we put the glass on the candle? The key here is to listen and let them think it through. No answer is too far out there or wrong at this step.

The observation step is key throughout any experiment, but take a moment and look at their components. What do they notice about them? How do they normally behave? What do they already know about them?

Narrow down your potential answers and decide on one or a couple of outcomes you think are most likely. This is your hypothesis.

Time to run the experiment! Encourage your children to keep watching what is happening. (In this particular observation, sight is going to be the key thing to focus on. Some touch is possible, watching out for the flame of course. And you can encourage smell and hearing for practice.

What did they observe? Now is the time for them to tell you everything they can about what just happened.

This is where we form the conclusions and apply the information we learned. Do they think this will always happen? How did the results match or differ from their hypothesis?

Real experiments always lead to more questions. What does your child want to try next? What would they change in the experiment? Does more water in the dish change anything? Can they try to suck up all the water? Would adding a different liquid change the results?

Even if you aren’t able to complete any of their additional experiment ideas, it is a good idea to think of ways to explore more. Plus it is amazingly fun to hear all the ideas kids have.

Text: Rising Water Experiment Science for Kids! Picture: shallow dish with blue water. Small votive candle in the center of the dish with glass upside down on top. Water level within glass has risen

This is a great experiment to do over and over. It’s fast, cheap and full of fun learning. It’s a must-do!

Let’s find your next fun activity!

Links to: STEM activities for kids Text: STEM Picture: raincloud in a jar experiment

Raising Water Experiment

How to do the raising water experiment that will wow kids!

Food Coloring (optional)
Lighter or Matches
Fill your shallow dish with enough water to cover the bottom. Add food coloring. (optional)
Place your votive in the middle of the dish.
Light the votive candle.
Place the glass upside down over the candle.
Wait for the candle to burn out and watch the water rise!

This is a science experiment that needs adult supervision and help. It uses fire and needs an adult to be safe.

To clean up, gently pull the glass off the candle. Make sure the candle cools and the water can go down the drain.

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Text: Fireworks Experiment Science for Kids. Picture: Red star cookie cutter with chemical reaction creating bubbles with glitter bubbling up

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Rising Water Candle Experiment

August 30, 2024 by Sarah Leave a Comment

Get ready to amaze your little ones with a rising water candle experiment! This experiment not only looks super cool, but it’s also a wonderful way to introduce some basic scientific concepts like what a fire needs to burn, air pressure, and equilibrium. Best of all, you only need a few household items, so it’s perfect for a spontaneous afternoon science activity!

Celebrations Family Unit Study Bundle

This rising water experiment is one of the hands-on activities from Birthday School .

If you’ve never heard of Birthday School before, you’re in for a treat! Birthday School is the perfect unit study to dive into during your child’s birthday month. You’ll learn about fun birthday games, some delicious (and maybe not-so-delicious!) birthday foods, make a colorful present, and so much more. It’s a wonderful way to harness all of that birthday energy and inject some celebratory fun into your homeschool routine.

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You can grab ALL of these celebration family unit studies in the Celebrations Family Unit Study Bundle (such a clever name, I know). All celebrations are presented with a secular framework, focusing on the magic of the holidays without religion. We know you will love them every bit as much as your child as you build memories to last a lifetime!

Check out a sample and grab your copy right here: https://shop.howweelearn.com/products/celebrations-bundle

How to Perform the Rising Water Candle Experiment

Below, I’m going to share with you exactly how to set up and perform the rising water candle experiment, the science behind what’s happening, and an optional extension activity.

For this experiment, you will need:

shallow dish
tealight or small candle
glass jar or vase
lighter or match
food coloring (optional)

Rising Water Candle Experiment Instructions

1. Pour some water into a shallow dish so it’s about 1/2″ full. You could also mix in a couple of drops of food coloring into the water if you’d like.

2. Float a tealight on top of the water and carefully light it.

3. Next, you’re going to place a glass jar over the tealight. What do you think will happen? Make your predictions!

4. After you place the glass jar over the tealight, you’ll notice the flame goes out. You’ll also see the water slowly move up inside the jar, pushing the tealight up with it! How does this happen? Read on to find out!

What’s Happening in the Candle Experiment?

Let’s chat a bit about what’s happening in this experiment and why!

For a candle to burn, it needs three things:

a heat source,

The heat source is the fire from the lighter or match, the fuel is the candle wax, and the oxygen is in the air all around us.

You can make the flame go out by removing either the heat source, fuel, or oxygen:

If you blow on the flame, it will go out because you removed the heat.
If the wax runs out, the flame will go out because there is no more source.
Or, you can make the flame go out by removing the oxygen!

When you place the glass jar over the candle, the candle quickly uses up all of the available oxygen in the jar, then the flame goes out.

But why does the water get drawn into the jar?

The heat from the candle makes the air in the jar hot. Hot air takes up more space, increasing the pressure inside the glass jar. You may even see a few bubbles escaping from the bottom edge of your jar as some of this excess air tries to escape.

When the flame goes out, the air cools off again, lowering the pressure inside the glass jar. Now, the pressure outside of the jar is higher than the pressure inside the jar. This creates a vacuum, where the water gets drawn into the jar until the pressure inside and outside the jar is the same. This is called equilibrium!

Optional Rising Water Extension Activity

Now that you know how this rising water candle experiment works, you can try changing some of the variables and predicting what might happen!

What happens if you change:

the size of the jar?
the size of the candle?
how much water is in the dish?

Do you think changing any of these variables will affect how much water is drawn into the jar? Try it and find out!

When we tried two tea lights and a vase, it sucked up ALL of the water (and ended up submerging the tea lights). That particular combination got a lot of oohs and aahs from the kids—and from me!

I hope your children enjoyed this experiment and learned something new. Now, let’s keep that hands-on learning going all year long with the Celebrations Bundle! Grab your copy right here:

https://shop.howweelearn.com/collections/celebrations-family-unit-study-bundle

Thank you so much for reading, my friend!

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Rising Water Experiment

Light a fire under middle school science and heat it up! Place a burning candle in the water and watch what happens to the water. Explore how heat affects air pressure for an awesome middle school science experiment. This candle and rising water experiment is a great way to get the kiddos thinking about what is happening. We love simple science experiment s; this one is super fun and easy!

Candle in Water

This candle experiment is a great way to excite your kiddos about science! Who doesn’t love watching a candle? Remember, adult supervision is required, though! We love simple science experiment s; this one is super fun and easy!

This science experiment asks a few questions:

How is the candle flame affected by placing a jar over the candle?
What happens to the air pressure inside the jar when the candle goes out?

💡 Make sure to check out all our chemistry experiments and physics experiments !

Click here to get your free printable STEM activities pack!

Candle in a Jar Experiment

You need to change one variable if you want to extend this science experiment or use the scientific method for a science fair project .

EXTEND THE LEARNING: You could repeat the experiment with candles or jars of different sizes and observe the changes.

💡Learn more about the scientific method for kids here .

Middle School Science
Elementary Grades Science
Tea light candle
Bowl of water
Food coloring (optional)

Instructions:

STEP 1: Put about a half inch of water into a bowl or tray. Add food coloring to your water if you like.

STEP 2: Set a tea candle in the water and light it.

ADULT IS SUPERVISION REQUIRED!

STEP 3: Cover the candle with a glass, setting it in the bowl of water.

Now watch what happens! Do you notice what happens to the level of water under the jar?

Why Does the Water Rise?

Did you notice what happened to the candle and the water level? What’s happening?

The burning candle raises the air temperature under the jar, and it expands. The candle flame uses up all of the oxygen in the glass, and the candle goes out.

The air cools because the candle has gone out. This creates a vacuum that sucks up the water from the outside of the glass.

It then raises the candle up on the water that enters the inside of the glass.

What happens when you remove the jar or glass? Did you hear a pop or popping sound? You most likely listened to this because the air pressure created a vacuum seal, and by lifting the jar, you broke the seal, resulting in the pop!

More Fun Science Experiments

Why not also try one of these easy science experiments below?

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

90+ classic science activities with journal pages, supply lists, set up and process, and science information. NEW! Activity-specific observation pages!
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Burning Candle in Rising Water Experiment w/ FREE Worksheet

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Get ready to WOW your kids with a super EASY science experiment for kids ! This simple rising water experiment uses common household items to demonstrate a couple scientifc principles such as fire and oxygen as well as air pressure for kids . This burning candle in water experiment is fun for preschool, pre-k, kindergarten, first grade, 2nd grade, 3rd grade, 4th grade, 5th grade, and 6th graders. Olders students will benefit using the free printable burning Candle in Water Experiment Worksheets as they explore why does the water rise in the candle experiment .

Rising Water Experiment

Have you ever looked through experiment ideas for kids on google, Facebook, or Pinterst and thought it looked cool, but were convinced it was too difficult and wouldn’t work. I get it! I have been there too! This rising water experiment is NOT one of those science experiments. This the burning candle experiment is actually super simple and uses common things you have in your kitchen already! So gather a few supplies and start learning with this air pressure experiment for preschoolers, kindergartners, grade 1, grade 2, grade 3, grade 4, grade 5, and grade 6 students. Whether you are a parent, teacher, or homeschooler – you will want to try this super neat candle experiment that is quick and easy. Plus there is a free science worksheet to help teach the scientific method with older elementary age students too.

Candle experiment

Start by scrolling to the bottom of the post, under the terms of use, and click on the text link that says >> Download <<. The science worksheet pdf file will open in a new window for you to save the freebie and print the template.

Burning Candle in Water Experiment

All you need to try this super cool science experiment are a few simple materials you probably already have on hand:

plate with raised rim ro bowl
ligther or matches
mason jar or glass
food coloring (we used blue to see it better)
playdough (optional for holding the candle in place)

The Burning Candle Experiment

Start out by putting the candle on plate or bowl with a lip. I suggest using a chunky tall candle so the water won’t overwhelm the candle and it has some stability. If you use a tall tapered candle, you may want some playdough to hold it in place.

Mason Jar Experiments

The amount of water used will really depend on the height of your candle and the lip on your bowl. But I’d say 1/2 cupr or so was right for us. We mixed our water with food coloring first and then poured it on the bottom of the dish.

I suggest filling out the pdf science worksheets at this point to help students make educated guesses or hypothesis!

Get ready to WOW your kids with a super EASY science experiment for kids! This simple rising water experiment uses common household items to demonstrate a couple scientifc principles such as fire and oxygen as well as air pressure for kids. This burning candle in water experiment is fun for preschool, pre-k, kindergarten, first grade, 2nd grade, 3rd grade, 4th grade, 5th grade, and 6th graders. Olders students will benefit using the free printable burning Candle in Water Experiment Worksheets as they explore why does the water rise in the candle experiment.

Burning Candle Rising Water Experiment

Please do a trial before you light it to make sure your candle will fit under the mason jar or glass. Light the candle and put a mason jar over the top of the candle.

WARNING: Fire is dangerous and this should only be done under the carefuly observation of a responsible adult. Please use common sense when completing this science activity.

Have students watch carefully. The candle will start lit, but won’t stay that way for long!

CAUTION: The glass will become hot to the touch. Please wait for it to cool down completely before touching; it should be handled by an adult with care.

Air Pressure for Kids

You will observe the candle going out, some bubbles forming around the bottom of the mason jar, and then the jar will begin filling up with water.

Why does the water rise in the candle experiment

The candle went out in the jar because it ran out of oxygen. Fire needs oxygen to live. When the oxygen ran out in the upside down mason jar the candle went out without us blowing on it. But something else happened when the candle was burning, the flame heated up the air inside the glass. The hot air expanded quickly and created higher air pressure inside the glass than outside the glass. To restore equilibrium, some of the high-pressure air inside escaped from under the glass. You may have seen tiny bubbles escaping from underneath the glass. When the flame extinguished, the air inside the glass began to cool down. Cooling air contracted, which in turn lowered the air pressure inside the glass.

The remainder of the blue water was sucked in to the mason jar.

Why does water rise in burning candle experiment

Why does the water rise in the candle experiment

Burning Candle in Water Experiment Worksheets

Students filled out the remaineder of the burgning cande in water experiment printable showing the results. After you explain what happened, ahve children write their conclusion.

Extensions Ideas:

Try using hot water or cold water instead of room temperature water; did it make a difference?
Use more or less water? Does that make a difference?
Use a larger candle or smaller candle; does the size of the candle matter?
What if you use multiple candles? Multiple candles would make the jar hotter and use up the oxygen quicker; did that make a difference?
Use milk or vinegar instead of water. Does the type of liquid change the outcome?
Will using a bottle with a more narrow neck change the results?

Have you ever heard of a lemon volcano? Kids are going to love this fun, creative,volcano experiment that screams summer! This simple lemon volcano experiment is perfect for curious kids from toddler, preschool, pre-k, kindergarten, first grade, 2nd grade, and 3rd graders too. All you need are a few simple materials to make some amazing erupting lemon volcanos!

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Looking for a fun summer activity for kids? You are going to love blowing colorful snake bubble. This sock bubbles activity is super simple and such an easy summer activity idea for toddlder, preschool, pre-k, kindergarten, first grade, 2nd grade, and 3rd graders too. It takes blowing bakcyard bubles to a new level making long, colorful snakes with a simple technique using a sock and a plastic bottle. You've got to try this bubble snake experiment.

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You start with a lighted candle on a plate of water. Cover it with glass and this is what happens.

Burning Candle Experiment With Water: Watch The Smokey Glass “Suck” Water In!

Cover a burning candle with glass and the surrounding water goes up inside the glass.

This burning candle experiment with water is pretty neat and one that will amaze many kids.

If you like quick experiments that you can do without buying a science kit for kids , this one is a good one to start with.

Before we move on, just a little reminder. This educational activity uses fire, so adult supervision is recommended.

With that out of the way, vamos a empezar! (Let’s start!)

oxygen, air pressure, candle experiments, water experiments

Doing This Experiment In The Gally Kids Headquarters!

As usual, we started this activity with colored water.

This is optional. But you get to see the water better when it’s a different color.

We chose red.

Then we followed the instructions which are all straightforward.

The first try wasn’t exactly a success as there was very little water that went into the glass.

We gave it another try and this time, it was a lot better. It was what we wanted and expected.

Then of course, we couldn’t stop there. We wanted to see if more water would get in if we put in another source of heat. So we put the lighted match in with the candle.

We change it up a little bit by adding another source of heat.. The result? amazing!

There didn’t seem to be much of a difference in the water level.

The smokey effect is pretty cool.

Step 3:Voila .. See the bubbles and the water gets "suck" in.

So we were happy with it.

Burning Candle Experiment With Water Materials

You will need:

water (colored ones are the best)

Burning Candle Experiment With Water Procedure

First, pour water into the plate.
Next, put the candle in the middle of the plate.
Then, light up the candle. Wait 30-seconds to 1 minute to make sure the candle is properly burning.
When it’s ready, cover the candle with the glass.
The candle will continue burning for a few seconds. But then when the candle turns off, this happens.
The water rises inside the glass!

Why Does The Water Rise In The Candle Experiment?

The water rises in this candle because of air pressure.

But that’s not all there is to it.

What happens is that when you cover the candle with the glass, the air inside it expanded because of the heat. But then when the candle burned off, the air inside it got colder. Cold air contracts so this left a space inside the glass. This also allowed the air inside the glass to have less pressure.

But, the air outside has more pressure. So it pushes the water in until the pressure inside and outside are the same.

Pretty cool and fun activity that educates as well!

Video: Water Rises Up Inside The Glass

Here’s the video of the burning candle experiment with water which we posted on our Gally Kids channel in Youtube . Don’t forget to visit us there! And if you want to get notified every time we post a new video, make sure you subscribe!

WATER-CANDLE EXPERIMENT TO TRY OUT WITH KIDS

The water-candle experiment is a great early science activity to try out with kids. We tried it with our almost 3-year-old many many times and he insists almost daily to repeat it.

If you want to know more about the science behind, you can read here (Harvard.edu).

Safe science experiments at home are a great way to ignite the natural curiosity of your little one early on. We chose this one, because Aiden loves water and fire. And it did not include any explosion or mess.

So, well worth to try it out! Here is what you need.

Materials for the Water-Candle Experiment

To do it at home, we used few things from our kitchen:

A clear glas bowl filled with some water.
A tea light
Small glas jar

Instructions

And that’s how it worked.

First, we placed the clear glas bowl with the water on his activity table. We divided the responsibilities – I was the one responsible to light up the tea light and place it into the water and Aiden was the one who covers the burning candle with the glas jar. Perfect!

After some seconds, the candles starts to dim and goes out. When the candle goes out, the water rises into the glas jar. The water level stays up for few minutes more, if your impatient toddler does not take the glas jar first and asks you over and over to repeated it again.

This simple science water-candle experiment for kids, has at least two aspects – a chemical and a physical one. Both a chemical and a physical reasoning are needed to explain what we can see. I found it a little bit challenging to explain it to my toddler, so we just enjoyed the science in action over and over again.

Here is a short video of one of our scientific sessions.

Happy Experimenting!

If you need more activity ideas, here is where you can find them !

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Burning Candle, Rising Water Experiment

Introduction: Burning Candle, Rising Water Experiment

I saw a short video of this experiment on Reddit and thought it would be an interesting science experiment to try with the kids.

Here is our recreation of the experiment:

Step 1: Materials

Below is a list of the materials you will need for the experiment.

Tall Glass with a slightly larger diameter than the candle
Food Coloring or Mio
Spoon (Optional)

Step 2: Add Food Coloring to Water

You can do the experiment with just water but colored water is easier to see. We used Mio instead of food coloring.

Step 3: Add Colored Water to Plate

You should experiment with different levels of water. We used about 1/4".

Step 4: Place Candle in Center of Plate

Candle should be placed vertical as shown.

Step 5: Light Candle

Light the candle. Note that a larger flame gives a more dramatic effect.

Step 6: Place Glass on Candle

Carefully place the glass container over the candle.

Step 7: Watch the Science in Action

I tried to grab some frames of the process. Notice how the colored water moves from the plate into the glass container. Once the candle flame goes out, you will see an inrush of water.

If you search for this on the web, you will see multiple ideas on how it works.

I took the explanation of Oliver Knill from the Harvard Math Department. He states in general terms: "The candle heats the air and expands it. This cancels the depletion of the oxygen temporarily and the water level stays down. When the oxygen is depleted, the candle goes out and the air cools. The volume of the air decreases and the water rises. The temporary temperature change delays the rise of the water"

For debate on the subject, see the following link:

math.harvard.edu

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Candle Water Experiment

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You won’t believe your eyes when a flame appears to be burning underwater in this super cool Candle Water Experiment! Let’s jump in and find out how to make a candle burn underwater!

Discover more Science Experiments With Matches here!

This cool science experiment for kids is a great way to demonstrate the high heat capacity of water! Your kids will be both entertained and educated with this experiment, but they will need some adult supervision.

Table of Contents

This post may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases.

Supplies Needed:

Tall Candle
Modeling Clay
Lighter or Matches

Underwater Candle Experiment

Cut a tall candle down to just below the height of your bowl.
Stand the candle up in the center of the bowl and secure it with modeling clay.
Fill the bowl with water to a height that is just below the top of the candle.
Light the candle with a lighter or matches.
Watch for a few minutes as the candle burns down below the water level!

Step 1: Cut a Tall Candle To Stand Below the Rim of Your Bowl

Remember that since this experiment does require sharp scissors and sizzling fire, adult supervision is required!

Now get ahold of a pair of scissors and carefully cut your tall candle down to a length that is just barely lower than the height of the bowl you will be using.

You might want to measure the height of your bowl from the inside bottom to the rim of the bowl to help get the candle to the right height. You can also just eyeball it and it should work just fine!

Step 2: Stick The Candle to The Center of The Bowl

After you have cut your candle down to the right size, get some modeling clay and work it into a nice round flat circle.

Use modeling clay to attach the candle to the bowl

Place the modeling clay on the inside bottom center of the bowl and then attach your candle to it with the candle standing up. Don’t be afraid to apply some pressure pushing the candle down to make sure it holds in place!

Stand a candle up in a bowl with modeling clay

This should secure your candle to the bowl with the candle standing up in the middle and center of the bowl.

Step 3: Add Water To The Bowl

Gently and carefully pour enough water into the bowl so that the water level is almost to the same height as the candle, but just a touch below the wick of the candle.

Pour water into the bowl with a candle in it

You just want to be careful not to pour the water too quickly or it could knock the candle over.

Step 4: Ingite the Candle

Okay now we are getting to the fun and exciting part! Again…with adult supervision grab some matches or a lighter and get that candle burning!

Step 5: Wait For The Candle To Burn Below The Water Level

Once the candle is burning, watch and wait for several minutes as the wax begins to melt and the candle starts to get shorter and shorter.

Eventually, the wick and the inside core of the candle will drop below the water level and keep burning while the outer edge of the candle wax stays higher with the water level.

This will give the appearance that the candle is burning underwater, but is that really the case!? Let’s dive into the fun science behind how this underwater candle experiment works to find out!

Candle and Water Experiment Explanation

The magical science behind this candle and water experiment is really thanks to the high heat capacity of the water in the bowl surrounding the candle.

As the wick of the candle burns, the hot flame melts the wax immediately around the wick, but the water keeps the layer of wax on the outside of the candle cold enough to not melt.

The water is able to keep the outside of the candle cold enough thanks to water’s incredible ability to absorb heat and energy, which is referred to as the heat capacity of water.

For another cool way to demonstrate the heat capacity of water, check out this How to Fireproof a Balloon experiment!

This is the same reason that the sun will heat up the air around us to a hot temperature much quicker than a swimming pool full of water will heat up!

So even though the wick and the flame have dropped below the water level, it will continue to burn because the outer part of the candle wax is still solid and acts as a barrier to keep the water from getting to the flame.

Eventually the wax on the outer diameter of the candle will soften enough to allow water to leak in and fill the area around the wick and extinguish the flame.

PIN THIS EXPERIMENT FOR LATER

More Fun Experiments For Kids:

Balloon and Candle Experiment
Hurricane In A Jar
Breaking an Egg With One Hand Experiment

December 1, 2021 at 11:38 pm

Thank you! We are so happy to hear that you enjoyed our simple and fun candle experiments, and I love how you tied them in with Hanukkah!

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Rising water experiment

Follow FizzicsEd 150 Science Experiments:

You will need

A clear glass cup that is taller than the candle
Adult supervision

Matches, a candle, play dough, a water bottle a glass and a plate on a desk

Instruction

Using the playdough, fix the candle to the bowl so that it sits upright inside the bowl.

water being poured into bowl with playdough and candle

Pour some water into the bowl.

With the matches, light the candle.

Clear glass cup over the top of the candle in the playdough and the water

Cover the candle with the glass cup. Watch what happens! If you want, you can add food colouring into the water to make the experiment more visible.

A man holding a soda can with tongs and a bunsen burner heating the can base

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What is happening?

You created an area of low pressure!

When the experiment is run you can see tiny bubbles escaping under the glass which shows that the air pressure increased inside the glass from the heated air as the candle burns. Once the candle runs out of oxygen, the candle burns out and the remaining air inside cools down. Cooling air contracts ( see liquid nitrogen on a balloon! ) which lowers the air pressure inside the glass. This created a pressure difference between the air inside the glass and the air outside the glass. This pressure difference caused the high-pressure air outside the glass to push the water down into the plate… allowing the water to be pushed upwards into the inside of the glass towards the lower-pressure air inside the glass.

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6 thoughts on “ Rising water experiment ”

Hi When I was at school 30 years ago the oxygen use causing the rise was taught. Since then, it is my understanding from lots of reading, that the reasons behind the rise are related more to temperature as described nicely by Steve Spangler below.

A common misconception is that the consumption of oxygen by the flame in the container is a factor in the water rising. There may be a slight possibility that there would be a tiny rise in the water from the flame using up oxygen but it’s extremely small compared to the actual reason. Simply put, the water would rise imperceptibly at a steady rate as the oxygen were consumed. You likely saw the level rise almost all at once and pretty much after the flame went out.

At first, the flame heats the air inside the container and this hot air expands quickly. Some of the expanding air escapes from under the vase where you might have seen some bubbles. When the flame fades and goes out, the air in the container cools and cooler air contracts or takes up less space. That contraction creates a weak vacuum – or lower pressure – in the container. Where’s the higher pressure? Right! It’s outside the container pressing down on the water in the dish. The outside air pushes water into the container until the pressure is equalized inside and outside the container. The water stops rising when that pressure equalization is reached. https://www.stevespanglerscience.com/lab/experiments/why-does-the-water-rise/

Hi Angela, You’re right and great spot! It looks like this explanation missed the other half of the answer and it’s been updated now. Thanks for the heads up!

Thanks a lot !!! You saved me …? Tmrw was my science test and I was desparatly searching for this answer …

Great experiment to try i tried it and it failed ):

Oh no! How did you set your experiment up? Usually, the failure happens when the water on plate isn’t high enough. Give it a go again!

Yeah I will(:

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Gilla:		Dela:

1 drinking glass
1 lighter or matchbox
Food coloring (optional)
Safety equipment: 1 fire extinguisher

Step 3 (alternative A)

Step 3 (alternative B)

Short explanation

Long explanation.

What happens if you put the glass over the candle very quickly?
What happens if you use a larger glass?
What happens if you use a taller, narrower, glass?
What happens if you use a different type of candle (for example, a small cake candle?
What happens if you use multiple candles (you may need a larger glass or a jar)?
What happens if you use a bowl of water instead (see below)?

Gilla:		Dela:

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Why does the water rise?

It's a very popular experiment ( eg ), from elementary school : put a burning candle on a dish filled with water, cover the candle with an inverted glass: after a little while, the candle flame goes out and the water level inside the glass rises.

The standard explanation (as I recall it) was that combustion "burns" oxygen, and the consummed volume accounts for the extra water that goes inside the glass. Is this correct? I remember feeling (years later) uncomfortable with the explanation, because "to burn" is certainly not "to dissapear": I thought that oxygen combustion produces (mainly) $CO_2$ and hence one oxygen molecule would produce another $CO_2$ molecule, and the volume would remain basically the same. Perhaps $CO_2$ dissolves into the water? I would doubt that.

To add to my confusion, others state that the main cause is not the oxygen combustion but the changes of air temperature, that decreases when the flame goes out and makes the air inside the glass contract... which would rather invalidate the experiment as it was (and is) traditionally taught to students.

What is the right explanation?

(image from here )

Update : As from webpage linked in accepted answer, there are several effects here, but it's fair to say that the "traditional" explanation (consumption of oxygen) is wrong. Oxygen (plus paraffin) turn into $CO_2$ (plus water) (a representative reaction: $C_{25}H_{52}+38O_2 \to 25CO_2+26H_2O$ ). This would account for a small reduction in volume ( $25/38 \approx 2/3$ ), even assuming that this is the complete chemical picture (it's not) and that water condenses ( $CO_2$ dissolves in water poorly and very slowly). The main cause here is thermal expansion-contraction of air.

home-experiment
physical-chemistry

$\begingroup$ Is there a stackexchange for chemistry? Maybe they could provide better help. $\endgroup$ – Lemon Commented Jan 4, 2012 at 1:58
$\begingroup$ @jak Not yet. $\endgroup$ – Manishearth Commented Mar 15, 2012 at 7:21
$\begingroup$ @Manishearth Yes there is - chemistry.stackexchange.com It is in beta, though. $\endgroup$ – Dave Coffman Commented Jul 28, 2014 at 22:06
$\begingroup$ @DaveCoffman look at the date on that comment. I moderate Chem.SE, I know about it :P $\endgroup$ – Manishearth Commented Jul 28, 2014 at 22:28
$\begingroup$ Geez - Sorry about that. $\endgroup$ – Dave Coffman Commented Aug 2, 2014 at 18:19

3 Answers 3

I found two web pages that explain the phenomenon quite well, and even looks into the misconceptions people have.

The candle flame heats the air in the vase, and this hot air expands. Some of the expanding air escapes out from under the vase — you might see some bubbles. When the flame goes out, the air in the vase cools down and the cooler air contracts. The cooling air inside of the vase creates a vacuum. This imperfect vacuum is created due to the low pressure inside the vase and the high pressure outside of the vase. We know what you're thinking, the vacuum is sucking the water into the vase right? You have the right idea, but scientists try to avoid using the term "suck" when describing a vacuum. Instead, they explain it as gases exerting pressure from an area of high pressure to an area of low pressure. A common misconception regarding this experiment is that the consumption of the oxygen inside of the bottle is also a factor in the water rising. Truth is, there is a possibility that there would be a small rise in the water from the flame burning up oxygen, but it is extremely minor compared to the expansion and contraction of the gases within the bottle. Simply put, the water would rise at a steady rate if the oxygen being consumed were the main contributing factor (rather than experiencing the rapid rise when the flame is extinguished). (1)

The page from Harvard goes into more detail on the argument versus the error for the incorrect statement.

Argument : Oxygen is replaced by Carbon dioxide. So, there is the same amount of gas added than taken away. Therefore, heat alone most be responsible for the water level change. Source of the Error : A simplified and wrong chemical equation is used, which does not take into account the quantitative changes. The chemical equation has to be balanced correctly. It is not true that each oxygen molecule is replaced by one carbon dioxide molecule during the burning process; two oxygen molecules result in one carbon dioxide molecule and two water molecules (which condense). Remember oxygen is present in the air as a diatomic molecule. [A reader clarifies the water condensation in an email to me as follows: If the experiment were done with the sealing fluid able to support a temperature greater than 212 F and the whole system held above this temperature then the water product of combustion would remain gaseous and the pressure within the vessel would increase as a result of three gaseous molecules for every two prior to combustion and the sealing fluid would be pushed out.] Argument : Carbon dioxide is absorbed by the water. Thats why the oxygen depletion has an effect. Source of the Error : This idea is triggered from the fact that water can be carbonized or that the oceans absorb much of the carbon dioxide in the air. But carbon dioxide is not absorbed so fast by water. The air would have to go through the water and pressure would need to be applied so that the carbon dioxide is absorbed during the short time span of the experiment. Argument : The experiment can be explained by physics alone. During the heating stage, air escapes. Afterwards, the air volume decreases and pulls the water up. Source of the Error : the argument could work, if indeed the heating of the air would produce enough pressure that some air could leave. In that case, some air would be lost through the water. But one can observe that the water level stays up even if everything has gone back to normal temperature (say 10 minutes). No bubbles can be seen. Argument : It can not be that the oxygen depletion is responsible for the water raising, because the water does not rise immediately. The water rises only after the candle dims. If gas would be going away, this would lead to a steady rise of the water level, not the rapid rise at the end, when the candle goes out. Source of the Error : It is not "only" the oxygen depletion which matters. There are two effects which matter: the chemical process of the burning as well as a physical process from the temperature change. These effects cancel each other initially. Since these effect hide each other partially, they are more difficult to detect. (2)

It clearly has more to do with the temperature differences than any conversion of gases. Especially considering that a volume of oxygen and carbon dioxide will be nearly identical to human eye observation.

4 $\begingroup$ I'd trust Harvard (second footnote I am guessing). $\endgroup$ – Skava Commented Jan 4, 2012 at 3:11
2 $\begingroup$ Yes "Skava", now go to bed! $\endgroup$ – Larian LeQuella Commented Jan 4, 2012 at 3:12
3 $\begingroup$ This answer is useful in pointing the best explanation I've seen (the second link), but the text is plainly copied other pages (should be formatted as quotes) and does not make clear the general summary/conclusion. $\endgroup$ – leonbloy Commented Jan 4, 2012 at 13:49
$\begingroup$ I'd question one thing from that answer, though: Nowhere is a vacuum created. There's always air in the glass, and it always fills the whole space not occupied by water. When the air cools down, it doesn't contract by itself, only its pressure goes down (intuitively: Since the molecules get slower, they hammer less onto the water surface). As result the water is pressed more in by the air outside than out by the air inside, and thus flows inside. This rising water compresses the air inside, which causes air density and thus pressure inside to rise again until equilibrium is reached. $\endgroup$ – celtschk Commented Jan 18, 2012 at 5:47
1 $\begingroup$ The second quotation seems to contradict the first one: first says "you might see some bubbles", the second one: "No bubbles can be seen". $\endgroup$ – Ruslan Commented Jul 4, 2018 at 9:25

I have not actually tried this experiment, but I will make at least a few observations:

Hypothesis 1: The burning of oxygen is responsible for the reduced air pressure.

Prediction - if the burning of oxygen is the sole cause of the change in pressure, we should expect to see the water in the glass rise at a more or less constant rate from the moment the environment is sealed until the burning stops. After the candle extinguishes, there should be no more change in water level.

Hypothesis 2: The reduction in temperature after the candle extinguishes is responsible for the reduced air pressure.

Prediction - if the temperature change is the sole cause of the change in pressure, we should expect to see no change in water level while the candle is burning (in the limit that the glass was lowered very slowly). After the burning stops, the water should rise at a rate related to the temperature drop and eventually stop as the experimental setup comes to room temperature.

In order to test which explaination is correct, you should be able to merely perform the experiment and match the observation with the prediction. Of course, in real life it may be a combination of these two factors or perhaps include other reasons not listed here.

Additional measures such as putting an oxygen indicator in the glass (say a fresh slice of apple) or a thermometer would provide further insight.

1 $\begingroup$ As oxygen is burned - how many moles of CO2 do you get for each mole of O2 used? $\endgroup$ – Martin Beckett Commented Jan 3, 2012 at 23:15
1 $\begingroup$ @MartinBeckett: Not to mention it's mostly carbon monoxide because it's imperfect burning. $\endgroup$ – Mike Dunlavey Commented Jan 4, 2012 at 3:15
1 $\begingroup$ @MartinBeckett: The pertinent equation seems to be something like $C_{25} H_{52} + 38 O_2 => 25 C O_2 + 26 H_2 O$. So for 1 mole of oxygen we have 0.65 moles of $C O_2$ - a moderate reduction, and this assuming water condenses. $\endgroup$ – leonbloy Commented Jan 4, 2012 at 14:40
1 $\begingroup$ @leonbloy - although with a smoky candle you do get a lot of CO. Plus since O2 is only 20% of air it would at most be a (1-0.65)*0.21 = 7% change in volume even with full combustion $\endgroup$ – Martin Beckett Commented Jan 4, 2012 at 16:26
$\begingroup$ @MartinBeckett: you are right, of course. See the Harvard link in the other answer for the complete picture. $\endgroup$ – leonbloy Commented Jan 4, 2012 at 16:36

I will make this into an answer because the idea behind this question is used in an ancient medical metho d which was still used by practical nurses and even prescribed by old fashioned doctors when I was a child more than half a century ago in Greece. It is now used in alternative medicine practices

The air inside the cup is heated and the rim is then applied to the skin, forming an airtight seal. As the air inside the cup cools, it contracts, forming a partial vacuum and enabling the cup to suck the skin, pulling in soft tissue, and drawing blood to that area.

I think it was the invention of antibiotics which diminished rapidly its use, which was mainly for bronchitis pneumonia and similar afflictions, at least in Greece.

As far as the question goes, no liquids to confuse the issue of its being a strongly temperature dependent effect.

$\begingroup$ Indeed, the practice is known as "cupping" and is often offered at spas and other health resorts. $\endgroup$ – AdamRedwine Commented Jan 4, 2012 at 13:15
$\begingroup$ +1 In spanish: "ventosa". I've seen it applied by my grandmother many years ago. $\endgroup$ – leonbloy Commented Jan 4, 2012 at 13:37

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Candle and Water Trick

As the temperature falls, so does the pressure

◊ Food colour

1. Put a very little water on a plate, and mix in a couple of drops of food colour.

2. Place a candle in the middle of the plate, and light it. Slowly bring a glass down on top of the candle until it is standing in the water, on the plate.

3. Watch what happens next!

The burning candle heats the air above it, including the air that goes into the glass. Once the glass is standing on the plate, the burning candle uses up all the available oxygen in the glass, then goes out. As it does so, the air in the glass cools, and as it cools, the air pressure in the glass falls below atmospheric pressure. Water is drawn into the glass until the pressure is equalised. You can turn this experiment into a competition by placing a small coin on the plate under the water and, offering students a variety of possible tools, seeing who can retrieve the coin without getting their fingers wet.

So how does this relate to atmosphere?

When we measure the air pressure at the surface of the Earth, we are literally measuring how much air is above us. If the air pressure falls, there is less air above us, if the air pressure rises, there is more air above us. The relationship between temperature and pressure is very important – as the temperature falls, so does the pressure and as the temperature rises, so does the pressure. That means that as air moves up in the atmosphere and the pressure falls (because there is less remaining atmosphere above) its temperature has to fall as well. Typically, the temperature of the atmosphere falls about 6°C for each 1000m you go up –so the tops of mountains are always much colder than the valleys below. This experiment also demonstrates how storm surges work – when the air pressure is low over a sea or ocean, the water level can rise. This can have devastating consequences – for example the North Sea flood of 1953.

Another experiment

For another experiment looking at the relationship between temperature and pressure, all you need is a plastic syringe (the sort sold in pharmacies for administering medicine to babies). With your finger over the nozzle, pour a little very hot, but not boiling, water into the syringe. There will be a bubble of air at the bottom, so you won’t scald your finger! Now use the plunger to push all but 3ml of the water out, then put your finger over the nozzle again, and pull the plunger out. As the pressure in the syringe falls, the temperature falls but so does the boiling point of water – you should see the water starting to boil!

More experiments and demonstrations

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Candle Under Glass Experiment

October 24, 2019
3-4 Year Olds , 5-6 Year Olds , 7-9 Year Olds , Chemistry , Fire Science , Household Items , Rainy Day Science , Science

We did this cool candle and glass experiment last week. The experiment teaches of role of oxygen in fire and its presence in the air. This one takes less than 5 minutes to complete it.

5 – 6-year-old kids can experiment this by noting time and they can learn how much oxygen is required to burn the candle. They can learn about smoke and wax.

How to do this candle and glass experiment

The simplest experiment to do but has a big science behind it. Don’t panic this science is easy for even kids to understand. Let us first do this experiment and study the science behind it.

Materials required for carrying out the experiment

Candle Lighter or Matches
Drinking glass
Ceramic dinner plate or wooden board (optional)

[*Product links are affiliate links. Your support is highly appreciated]

Arrangement

Place the candle on the plate. Keep the matchbox and glass tumbler ready.

Light the candle and leave it for some time and then close the candle with a glass tumbler so that you can see through the light.

flame size reduces in seconds light and candle experiment

After a few seconds, you can see the flame comes down slowly and eventually goes off. You can try opening the glass when the flame is low to see how it picks up oxygen again and the flame goes higher.

You can also see a small sediment of moisture in the inner walls of the glass. That is a proof that fire releases H2O.

Yes, the experiment is over. Now, try these and share your experience with us.

Now you can do this using a stopwatch and check the time taken for the light to go off after closing the candle with glass.
Use the candle of different size and check the timing.
Also, use bigger and smaller glass to check the timing.

Do this experiment with kids and allow them to make the observations.

Therefore oxygen is required for the candle to burn for a long time.

Detailed science with terminologies

Hydrocarbons present in the wax are converted to carbon dioxide and steam and this chemical process is called combustion. The oxygen gets pulled at the bottom and the wick draws the fuel. This will provide heat at the top and that makes air hot to rise up. This is how a candle burns. The steam part gives the blue color to the fire. The unburned carbon deposit makes the walls nearby black. Better oxygen means brighter the flame. Match stick is required to ignite and that produces the activation energy to start the entire burning process.

The chemical equation for your reference

Methane (hydrocarbon) + Oxygen –> Carbon dioxide and Water

CH4 + 2 O2 –> CO2 + 2 H2O

Check scienceline for more science facts. Also, read candles.org explanation to master the science behind candle and science experiments.

When the candle is placed in the jar it limits the flow of oxygen and hence the candle flame goes off.

Oxygen is the fuel for wax and makes the wick burn. When the candle is closed with the glass jar the oxygen supply is stopped. Initially, the candle burns by making use of the oxygen within the glass and slowly when there is no oxygen the flame goes off.

The candle that is the shortest will go out first. It is because the CO2 is denser than air so it will settle down at the bottom eventually putting off the fire.

Glass is also prone to crack and break due to heat. Check out for heat resistant glassware and use them for this experiment.

When the candle is lighted the heat of the flame will melt the wax first near the wick that is on the top. Thus the wax will melt and that liquid wax gets drawn up again by the wick due to capillary action. The flame’s heat vaporizes the wax in the liquid state and that will initiate the hydrocarbon break down process. The hydrocarbon breaks down further into molecules of carbon and hydrogen.

Combustion is the chemical reaction happening in the candle burning process. Wax is derived from petroleum and is a carbon chemical and it reacts with the oxygen present in the air. This process creates CO2 which is a colorless gas.

Yes and no. Yes if it is pure beeswax. No, if it is not a pure wax. Candles made of pure beeswax will produce no smoke and cleanses the air around. It does this by releasing negative ions in the air. Such released negative ions bind with the toxins and remove them eventually from air. Also, natural pure beeswax burns slowly, when compared to paraffin candles and hence they last for long time.

Candle burning requires oxygen and that is present in the air naturally. When we close the candle with jar, then oxygen flow is limited and once all the oxygen present is exhausted the candle gets extinguished.

Overall, stay around and explain to them to have fun.

What inspired me to do this experiment?

Let me share my experience in how did I arrive at doing this experiment? During one summer we had a massive power failure. My little ones had never been used to such a situation ever. But this time the situation was tough and they had to spend the whole night without power. That is when I lit a candle for light while we had dinner.

As usual, my curious elder daughter asked me how does a candle burn. Why does it not require electricity as lights and fan do? How come it gives brightness as an electric bulb does. She bombarded me with questions I was like feeling glad that she thinks all these things. At the same time, my naughty little younger one as usual in her style started doing fun things. She blew the candle and sang “happy birthday”.

We finished dinner and suddenly my little one using her empty glass covered the candle. In a few minutes the candle went off. I lighted the candle and told her not to play with fire. Again in few mins when I was away she did the same job to check if the light goes off. It did go off and my elder one was puzzled to know why it happened.

Her question was when there is more air candle goes off that’s exactly what happens when we blew the candle. But here the contradiction happens and when the candle is closed it should not go off as airflow is cut. Then why it happens. I told her that there is a science behind that action.

Now, we started doing this experiment to explain the concept to the kids.

water candle and glass experiment

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