candle water bottle experiment

Burning Candle Rising Water Experiment

Your kids will be amazed by this simple burning candle rising water science experiment. This rising water experiment will teach your kids the effect of air pressure.

This burning candle in water is one of those science experiments that appear like magic. 

With just a few items and a few steps, you can demonstrate to your how to rise the water inside the cup or jar without ever touching it.

Get your camera ready, your kid is going to have his mind blown by this amazing “why does the water rise” science experiment!

Burning Candle Rising Water Science Experiment

Materials: .

• A plate with a raised rim or a shallow bowl
• Lighter or matches
• Drinking glass or mason jar
• Optional: food coloring 
• Optional: Playdough
• Free rising water experiment worksheet (download directions at the bottom of the post)

Instructions: 

1. Place the candle in the middle of the plate or bowl.

2. Optional: If your candle can’t stand by itself, use some playdough to help it stand upright.

3. Optional: Mix water with food coloring in a separate container. The food coloring helps you see the rising water better.

4. Pour the colored water into the plate (to about 1 cm in depth).

5. Light the candle with a lighter or match.

If you are using the free rising water experiment worksheet, you can ask your child to draw his prediction of what will happen when you place the glass over the candle on the paper.

6. Turn the glass or mason jar upside down and place it over the candle.

7. Watch what happens to the water when the fire is still burning, and what happens when the fire extinguishes.

Did your kid’s jaw drop when the water rises when the candle went out?

Mine loved watching the sudden rise in water level inside the glass so much that we did the experiment over and over again until the candle couldn’t light anymore.

Don’t forget to have your child write or draw his observation in the rising water worksheet! Then read on to find out why the water started flowing into the jar after the candle was extinguished.

The Science Behind the Rising Water Experiment

Have your kids make an educated guess (hypothesis!) on why did the water rise when the candle went out, and why did the candle go out in the first place.

The candle went out without us blowing on it because it ran out of oxygen. The flame used up oxygen as it burned, and since the candle was trapped inside a glass, it quickly used up the available oxygen. Without oxygen inside the glass, the candle could not keep burning.

When the candle was still 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 cooled down. Cooling air contracted, which in turn lowered the air pressure inside the glass. 

Just as before when air rushed out from the glass to balance the air pressure between the inside and outside of the glass, now air wants to get in. As a result, the high-pressure air outside the glass pushes on the water, forcing the water into the glass. 

Visually, we can see the water level rising until the air pressure inside the glass is the same as the air pressure outside the glass.

Science Extensions to Try

What variables can you test to see how they impact the water rising?

• Use hot water or cold water instead of room temperature water. Does the temperature of the water matter?
• Use a larger candle or smaller candle. Does the size of the candle matter?
• Use multiple candles. Does the increase in candles (and hence, larger flames) change the water level?
• Use a different liquid like vinegar or milk instead of water. Does the type of liquid change the outcome?
• Pour more or less water in the plate. Does the amount of water affect how much water gets pushed into the glass once the flame goes out?
• Change the drinking glass to a bigger or smaller drinking glass. Does the size of the drinking glass matter?
• Use a drinking glass with a narrower neck. What do you observe?

Final Thoughts on the Burning Candle Rising Water Experiment?

If your kid is like mine and wants to do this experiment multiple times, you might find that the candle goes out right away. If that happens, blow in the glass and wave it in the air and then try again.

What happens is the air in the jar is still depleted. You need to replace the oxygen in the glass before placing it over the candle.

I hope your kid is as amazed by the burning candle rising water science experiment as mine!

YOU MAY LIKE:

• Ice Fishing Science Experiment
• Rainbow Walking Water Experiment
• Magic Melting Skittles!

About The Author

3 thoughts on “burning candle rising water experiment”.

Very cool experiment! My grandkids loved it. But how can you get the water to go back down? We’ve tried using a blow dryer on the glass, to heat up the air inside.

We have not tried getting the water back down besides breaking the vacuum by picking up the jar. You are right to try and make the air inside hot again, but I am guessing the blow dryer couldn’t make it hot enough. Maybe try the other way and make the outside air cool? I would love to figure this out, I will get back to you after I conduct some experiments!

Hi. I love it .very nice experiment. I want to told something I am take participate in the STEM competition. in year 2019-in subang 2020-online (covid-19)

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Getting the facts right

Photos of the experiment

An exhibit of explanations

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

Appendix: the ideal gas equation

Added March 20, 2011

Added September 26, 2011

Added November 20, 2011

Added January 23, 2012

Added February 5, 2013

Added January 21, 2014

Added March 30, 2021

Added January 28, 2024

Candle and Rising Water Science Experiment

October 6, 2021, join the conversation, categories/tags:, ages 8-10 ages 11+ stem activities, want these great ideas sent right to your inbox sign up for the newsletter..

Demonstrate the power of air pressure with this cool candle and rising water science experiment! This is one of those experiments that will make kids say “oooooooh!” and “wow!” I always love that.

This year, I’m teaching a middle school science class at our local co-op, and this experiment was in our textbook. The kids were so impressed! We added a few more variations to it and had so much fun with it.

In this science experiment, we’ll be exploring two things:

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

Supplies Needed for the Candle and Rising Water Science Experiment:

• A pie plate – you can use metal or glass, but glass is nice so that you can see through it
• A tea light candle
• A taller candle such as a votive
• Modeling clay
• Glass jars in 2-3 different sizes. Should all fit over the candles.
• Matches or a lighter
• An adult to handle the flame
• A measuring cup that can pour
• Food coloring

Part 1: What happens to a candle flame when you cover it with a jar?

Start by placing the tea light in the pie plate. Don’t add water yet. Light the tea light and watch it burn. How long will it burn? It should continue until it runs out of wax, but you don’t need to let it burn that long. Let the flame burn long enough that kids can tell the candle won’t just go out on its own.

Then light the tea light and cover it with a jar. The flame will go out after just a few seconds!

We compared three different sizes of jars to see how long the flame will last. It’s easy to use the stopwatch on your phone to time the flame.

One note – be sure to look at the capacity of the jars because shapes can be deceiving! We used a 6 oz jar, a 13 oz jar, and a 24 oz jar. We had two 24 oz jars that appeared to be different sizes, but were actually the same when we read the labels!

Discuss with kids that the flame went out because the candle did not have access to more oxygen. In order to burn, a flame must have heat, fuel, and oxygen. The larger jar should have allowed the flame to burn for the longest amount of time.

Part 2: Rising Water Science Experiment

Now here comes the really cool part!

Fill your measuring cup with water and add a couple drops of food coloring.

Place the tea light in the pie plate. Pour water into the pie plate so that it just covers the bottom. You don’t want the water to be very deep.

Light the candle, and then cover it with a jar.

Watch the water carefully. As soon as the candle goes out, water will begin to enter the jar! The water will rise up higher than the level in the rest of the pie plate! Science is SO cool.

We tried several different combinations of candles and jars, and I didn’t get photos of all of them.

If you try a taller candle with this same jar, the flame will go out faster since it’s closer to the top of the jar. We used a votive candle, and to make it even taller, we put some clay underneath it.

We also tried the taller candle with a spaghetti sauce jar that had a narrower opening. Because of the narrow opening and bigger candle, the water appeared to rise MUCH higher!

But, I also know that to some extent, more water DID enter the jar. When we did this at our class, ALL of the water was sucked into this jar when it hadn’t all been sucked in before!

With the spaghetti sauce jar, the tea light candle floated and looked really cool.

How does the candle and rising water science experiment work?

The science behind this cool science experiment is very interesting!

When you lit the candle, the heat warmed up the air in the jar. The hot air expanded, which led to higher air pressure. This caused tiny air bubbles to escape under the edge of the jar to equalize the pressure. You may have seen air bubbles escape from the jar during this part of the experiment.

When the candle went out, condensation formed at the top of the jar, and the air in the jar cooled. The air in the jar dropped in pressure because of the reduction in temperature, which caused water to enter the jar to equalize the pressure.

When you lifted the jar out of the dish, you probably heard a “pop” sound as the seal broke! The changes in pressure created a vacuum in the jar.

Have fun with science!

Need more simple science experiment ideas? We’ve got tons of projects that are perfect for elementary and middle school.

Here are 25+ Cool Science Experiments with Simple Materials .

Thea Olivier Oct 7, 2021

Wow indeed, we've had these experiments way back when I've been at s chool. I can not waite for my 2 grandsons to get older!!!!

Kathryn Jan 18, 2022

Looking forward to trying this today with my family. I just recently found your site and I am already so thankful for your material! We did the snowstorm in a jar you posted, and looking forward to trying more science experiments, and the card games you have on your site! Your site is wonderful! I'm looking forward to looking around your site more :) Thank you!

Mel Apr 1, 2022

I’m wondering if you can share what sci curriculum you use.

Rachel Nadeau Apr 6, 2022

I teach science and use this experiment in my class. FYI air pressure rises with colder air temperature and lowers with warmer air temperatures, which is opposite from your reasoning.

Sarah Apr 6, 2022

Well, yes and no. If you're talking about the weather or the air in a room, cold air sinks because it is more dense than warm air. But in a closed container, the pressure will increase when you increase the temperature. Think about an Instant Pot... when you turn it on, the temperature gets warmer inside the pot, but that doesn't mean the pressure is lower!! Same with car tires. In the winter, your tire pressure lowers when the temperature gets colder. Heat causes molecules to have more energy, which creates higher pressure when the molecules don't have room to spread out.

Kathleen Guillot Nov 8, 2022

Colder air produces an anticyclonic movement as it falls creating a high pressure area. Higher pressure at ground level. Cyclonic movement is air pressure being released or warm air rising creating a low pressure area. When these two areas are side by side, the higher pressure will always flow towards the lower pressure creating wind.Think a deflating balloon. The bigger the difference in pressure, the stronger the air flow.

Pierre Mar 10, 2024

No. The air pressure goes up with temperature. You are confusing this with air density as hot air is lighter than cold air.

The hot temperature increased the pressure of air inside the glass which caused the air to escape the glass. After the air cooled down inside the glass, the pressure inside the glass went down.

Paula Apr 2, 2024

Can't wait to try this in class and with my grandsons!

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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.

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!

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!

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.)

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.

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.

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.

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.

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!

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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Burning Candle Rising Water Experiment

• December 3, 2020
• 5-6 Year Olds , 7-9 Year Olds , Chemistry , Fire Science , Physics , Rainy Day Science

In our previous experiment , we discussed the candle covered with glass. The basic science behind was the oxygen limitation that made the candle go off.

In an extension of that science activity, I am now going to share another experiment with you. It is also to do with candles and glass, but with a twist.

Apart from the oxygen limitation that puts the candle off, there is also low pressure created in the glass that leads to a vacuum.

This will cause some effects and that looks like magic to kids but the science to all adults. So let us do this magic to our kids and also explain them some science.

Things required

• Ceramic or glass plates
• Glass tumbler
• Matchbox with stick

Steps involved

Fill the plate with water.

Place the candle on the plate and lit it. You can see the candle glowing brightly.

It may float or stand on the water in the plate based on the weight of the candle.

The presence of water does not make any difference to the candle at this stage.

After sometime invert the glass tumbler and place it on the glowing candle.

Imagine the glass will close the candle. In a few minutes, you can witness candle blowing off as the closed glass limits oxygen in the space surrounding the candle.

Another thing you will witness is now the water in the plate enters the glass and you will see the level rising constantly.

Science Behind Candle Rising Water

The basic science here is the lack of oxygen puts off the candle in step 2. At the same time lack of oxygen also lowers the atmospheric pressure and creates a vacuum.

This leads to the water entering the glass from the plate. You can see this like the water level rises in the glass.

Detailed science with chemical equations

The water level rises to 1/10th of the glass before the candles go off is importantly you must note.

There is no air bubble formed. The water level will stay for few minutes once the candle goes off completely.

So both the candle dies out and water rises happens concurrently.

Chemical equation

Oxygen + Candle (wax/paraffin) à Water and Carbon dioxide

O 2 + C n H 2n+2 à H 2 O + CO 2

I have an exercise for older kids here. Yes, ask your older kids to balance the chemical equation taking n as 1. Post the answers for learning.

The oxygen is 2 times more than the carbon dioxide released and hence the air volume reduces.

Let me also explain the physics behind this experiment for physics fans!

Physics facts

The burning candle produces heat which heats the air and thus expansion happens. This will cancel the oxygen depletion slowly and the water level remains down.

When oxygen gets saturated in the glass the candle goes off and the air begins to cool and volume decreases.

The reduction in air pressure will create a vacuum and hence water level rises.

Also, water initially is in the gas state when there is heat around and later it condenses and rises in level as water.

The same process or science is applied to how storms and hurricanes are formed.

When the sun heats up the air causing its density become low which is the reason for formation of wind and storms.

The high density air moves into the lower density air pockets. When there is enough wind referred to as ‘hurricanes’ causing the water rise and lifted up out of the ocean.

• This experiment is magic for kids aged 3 to 5.
• You can teach some science to kids 5 – 8 as they will know about oxygen etc.
• 8 -12-year-old kids can benefit from the chemical equations and the detailed science of this experiment.

As I always alert you, please make sure to assist or monitor kids when they do this experiment.

It involves fire and you must be around to avoid any accident. Also, dealing with glass dishes needs support which you must provide.

Depending on the age of your kid you decide whether you must take their help or help them or just be around. However, we advise you to be present irrespective of the kid’s age.

Interested in More Air Pressure Experiments? Explore the list below

DIY Drip Drop Water Bottle

Balloon Powered Car

Make a Balloon Rocket

We have tried answering a few usual questions that might arise in the kid’s mind. My little one always ask questions upon which I fumble many times. So here you go with ready-made answers as well.

Twice the time of oxygen is burnt than the available CO2 that decreases the air pressure and hence water level rises. The air cools soon after flames go off and the molecules slow down making the water vapor condense to moisture.

The heat of the flame will start melting the wax near the wick and the liquid wax is drawn up to the wick due to capillary action. The flames heat will vaporize the wax and break them into molecules of oxygen and carbon.

The candle is put off by placing the lid on the candle that is lit. It is another way to extinguish the candle. The lid is placed on the flame which immediately cuts off the oxygen and thus puts off the candle.

The wick gets close to the glass the wax burns off and heats the glass. This might lead to the explosion of the glass. However, when water is kept on the glass this explosion is prevented.

As long as the pressure is low the water rises and when the pressure level equalizes the water level stops rising.

Place the glass flat on the plate to prevent air bubble forming. In case if it is tilted, then the air bubbles will form due to the difference in the pressure level between the inside and outside surface.

When you observe the tall and short burning candles closed with a glass container, surprisingly the tall candle goes out first because the carbon dioxide released travels upwards and suffocates the tall candle making the cold air sink. The short candle utilizes the oxygen in this cold air and stays on for some more time. When all the oxygen is used up, the short candle also dies.

Yes, place a candle in the bowl containing water and lit it. Slowly it goes down melting the wax which forms a protected wax around the wick. This allows the candle to stay on for good amount of time even though the flame has reached the level lower than the water. And of course, after a while water gets into wick and turns the flame off.

Modifications you can try with this experiment

 Here are the few variations to further explore the scientific concepts in this experiment.

• Change the amount of water taken in the plate and observe how does it affects the water level rise.
• Discuss on what happened to the water when the candle is lit.
• How does temperature changes happen when we use different types of colored water?
• You can use colored water made of food coloring, milo, liquid dyes, powdered dye etc.
• Experiment on hot water versus cold water and observe the temperature and air pressure changes.
•  Also try the experiment using two candles versus one candle or more candles etc.
• Use different liquids instead of water and check what are the changes and results.
• Try with different candle weight and height
• Change the glass to narrow and broad
• Make colored water and also increase/lower the water level in the plate
• Try not to lit a candle before and light it only after placing the glass. Yes, you need to lift it a bit and light it. Preheating is avoided to observe for any changes in the results.

Share the results with us that will let all our readers know what happens with all these modifications. In the meantime, I will also try different twists with my kids and post my experience.

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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!
• Best science practices posters  and our original science method process folders for extra alternatives!
• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
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~ projects to try now ~.

Why Does Water Rise? Best Science Experiments for Kids!

Why Does Water Rise? Best Science Experiments with Water for Kids! Looking for one of the best science experiments for kids? Try this popular “Why Does Water Rise?” experiment and incorporate some TECH to prove the science.

It’s like magic and kids love watching this fascinating science experiment, but what is actually happening when you place a glass over a lit candle in a bowl of water? I set my two little scientists the task of finding out. And if you are looking for an awesome science fair idea, in our opinion this is a winner!

Why Does Water Rise? Vacuum Science and STEM Activity

What you will discover in this article!

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Check out our video of this and you’ll know why you have to try this yourself.

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Supplies and Tools

A shallow bowl or dish A candle Water (adding a few drops of food coloring makes it easier to see what is happening) Lighter A large glass jar (we used a flower vase)

And if you have budding scientists you will also need a non-contact infrared digital thermometer . This is a fantastic way to bring in some technology to your science and make the leap into STEM activities.

Set your candle on the plate and pour approximately 1/2 to 1 cup of water on the plate. Light your candle, then place your jar (or vase) upside-down over the candle.

Then sit back and watch one of the best science experiments ever!

My youngest thought it was magic, and both my kids were amazed.

As the candle goes out, all of the water is sucked up into jar. The water rises! But why does water rise?

Very quickly my oldest assumed it had to do with the burning candle using up all the oxygen because the water would rise as soon as the candle went out. He hypothesized that the lack of oxygen was causing a change in the pressure inside the jar.

He was right that the candle went out because it ran out of oxygen, but that isn’t what causes the water to rise according to our friends over at Harvard .

It was time to break out the non-contact digital thermometer.

We did the experiment again and this time my oldest took temperature readings.

Very quickly the numbers climbed to over 23 degrees Celsius as the candle burned inside of the jar.

But as the flame weakened the temperature numbers started dropping. Then the candle went out and the water started climbing. The faster the water climbed the faster those numbers dropped. Overall it lost 2 degrees in a matter of seconds.

The vacuum created was so strong it sucked up all the water and even created bubbles as it sucked in air too once it had pulled in all the water from our plate.

Extension Activities

Alter how much water you use. How does it affect your results? What is the maximum amount of water your set up can suck up?

Now change your glass container to something bigger or smaller. How does that affect your results? (Hint we found a narrow neck gave us the best demonstration of water rising.)

Does changing your candle for a bigger or smaller one affect the results?

How does changing the temperature of your water affect the results?

This is one of the best science experiments because it demonstrates what happens to a flame as it runs out of oxygen and also how a rapid temperature change can create a vacuum or suction by altering the air pressure inside the jar. Not to mention it’s like magic! Bound to impress, especially at that science fair. And with all the adaptions and variables you can alter, you can make this traditional activity, uniquely yours.

Bonus Science Experiment

On a clean plate place a lit candle and cover with the jar. Once it goes out, gently lift the jar and relight the candle. Try to place the jar over the candle.

What happens? The candle immediately goes out!

Because the air in the jar is still lacking oxygen because it was all burned off. Blow in the jar a few times or move it around to replace the oxygen, then try again. Once you replace the depleted oxygen in the jar you can position it over the candle again and it will stay lit until it burns off all the oxygen again.

This was a great little side demonstration. Even though we couldn’t see it, the chemical composition of the air inside of the jar is changed by the burning flame and it takes time and air movement to bring oxygen back into the container. A fantastic way to show that even though we can’t see it, science is happening all around us.

More Science Experiments for Kids

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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!

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

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?

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Science Experiment for Kids

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• This set is for personal and classroom use only.
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Beth Gorden

Beth Gorden is the creative multi-tasking creator of 123 Homeschool 4 Me. As a busy homeschooling mother of six, she strives to create hands-on learning activities and worksheets that kids will love to make learning FUN! She has created over 1 million pages of printables to help teach kids ABCs, science, English grammar, history, math, and so much more! Beth is also the creator of 2 additional sites with even more educational activities and FREE printables – www.kindergartenworksheetsandgames.com and www.preschoolplayandlearn.com. Beth studied at the University of Northwestern where she got a double major to make her effective at teaching children while making education FUN!

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Science in School

A twist on the candle mystery teach article.

Author(s): Steven Ka Kit Yu

Three candles of different heights are lit in a closed space. Surprisingly, the longest candle goes out first. Can you solve the mystery?

In a classic demonstration of the candle mystery, three lit candles of different heights are covered with a gas jar (see figure 1) and the tallest candle goes out first. This happens because carbon dioxide produced from burning has a higher temperature, so it rises and accumulates at the top of the jar. Then the carbon dioxide gas cools down, falls, and extinguishes the tallest candle first. This article builds on the classic demonstration of the candle mystery and advances it in three ways. Firstly, the 5E instructional model [ 1 ] is used to develop learning activities that require students to construct, revise, and apply scientific explanations in unpredictable contexts. Secondly, these activities aim to help students test their hypotheses by using and coordinating multiple pieces of evidence. Thirdly, these activities include experiments and discussion tasks to challenge students to predict and explain results. By adding variables to the candle mystery, you can engage students and promote critical thinking and scientific understanding.

The experiments can be conducted as demonstrations or as hands-on practical work for small groups of students. They are quick and easy. The activities can be used with students aged 11 to 16.

Safety notes

• Follow all fire safety regulations and have fire extinguishing materials on hand.
• Wear safety goggles throughout the experiments. If students are performing any steps themselves, they should do the same and be warned to take care around open flames.
• The gas jar can become very hot during and immediately after candles are extinguished. Students should be warned not to touch it with bare hands and care should be taken (e.g., wear heat-resistant gloves when lifting the hot gas jar and/or lift the gas jar when it has cooled to room temperature).
• Make sure all candles are extinguished after each experiment.
• Ensure sufficient ventilation, for example, by opening windows.

Activity 1: Engaging and exploring student ideas for the candle mystery

This activity aims to set up a scenario to engage students in inquiry. When three candles of different heights are lit and covered with a gas jar, students are prompted to predict and explain which candle they think will go out first. Allow 40 minutes for the prediction discussion, experiments, and collaboration.

• Large gas jar (large enough to cover three candles)
• Three candles of different heights
• Heat-proof mat
• Hot-air gun, 240 V, 2000 W (optional: used to heat the blade to cut candles to different heights)

Worksheet 1

Preparation

Before the lesson, the setup should be prepared by the teacher or teaching assistant.

• Cut three candles to different lengths with a hot blade preheated by a hot-air gun (see figure 2).

• Align the three candles on a heat-proof mat, close enough that they can be covered with the gas jar.
• Cover the three candles with the gas jar (without lighting them, figure 3).

Practical tips :

• To ensure fair testing and expected results, ensure that the wicks are identical in length, and that the heights of the candles differ significantly.
• Perform a test run before the lesson to check that the setup works and to get a sense of how long it takes for the first candle to go out.
• Show the setup to students and encourage them to think about what would happen if we lit the candles (and replaced the gas jar). Ask them which candle they expect to go out first.
• Have them write down their own ideas first (and record them in worksheet 1) and then optionally have them discuss this in groups and then with the class. Ask them which candle they expect to go out first.
• Remove the jar, light the candles, and watch what happens. Depending on the setup (e.g., candle length, jar size), the candles should go out within a few minutes. Students often find the result (the tallest candle goes out first) mind-blowing.

• Optional: have students repeat the experiment (or watch a recording) and record the times required for each candle to go out. Combine the results and draw a graph.
• Discuss the results and encourage students to reflect on their initial predictions. Were students surprised by the results? Did the results match their predictions? Does it make them think differently about their explanation?
• A more in-depth discussion about why the tallest candle goes out first follows in Activity 2. If Activity 2 is not being used, part 1 (Why does the tallest candle go out first?) of Activity 2 can be carried out here.

Watch a demonstration of Activity 1.

You can adopt the think–pair–share approach to engage with student thinking in step 1. In this approach, students are asked to predict and explain individually which candle would go out first. They then share their predictions and explanations in groups of three or four, followed by a whole-class discussion. You can capture students’ initial ideas and reasoning and stimulate students’ thinking using the following questions:

• Why do you think the tallest or shortest candle goes out first, or why do you think the candles go out at similar times?
• After listening to your classmates’ ideas, would you change your prediction?
• How would you convince others that your prediction is correct?

Activity 2: Explaining the candle mystery

Instead of explaining to students that hot carbon dioxide rises to the top of the jar and extinguishes the tallest candle first, a discussion to help them think it through themselves will lead to better understanding. It is important to allocate time and support for students to reflect thoughtfully. They can test the explanation by monitoring changes in carbon dioxide concentration [ 2 ] and the temperature inside the gas jar. The activity takes about 40 minutes.

• Three plastic bottle caps
• Adhesive putty like Blu Tack or some adhesive tape
• Bicarbonate indicator solution (10 ml)
• Three temperature sensors (e.g., PASPORT chemistry sensor)

Evidence cards

Worksheet 2

• Timer (optional)

Part 1: Why does the tallest candle go out first?

• Ask students why they think the tallest candle goes out first. If they mention CO 2 , you can prompt them to think about how to test their hypotheses.
• Why did the candles go out before they burned down?
• How does the air in the jar change as the candle burns?
• What chemical process creates flames? What are the outputs of combustion?
• What happens to gases when they’re heated?

You can also link this to the real-life situation of escaping from fires by asking questions like:

• What are the essential actions to be followed in case of a fire inside a building?
• Why do we stay low to crawl through smoke-filled rooms or corridors?
• You can use the evidence cards (figure 4) to help guide the discussion.
• Once they have some ideas involving CO 2 build-up and temperature differences, ask how they would test their hypotheses. Encourage them to think about what variables would need to be kept the same to ensure a fair test.
• The experiments in parts 2 and 3 can be used to investigate some of these variables, or you can come up with your own.

Part 2: Monitor the carbon dioxide concentration

Safety note

A safe distance between the flame and Blu Tack/tape should be maintained to avoid melting of the Blu Tack/tape.

• Set up the experiment as for Activity 1. You can use the same candles but ensure the wicks are the same lengths.
• Fill three plastic bottle caps with bicarbonate indicator and use Blu Tack or tape to stick them at different levels inside the gas jar (figure 5).
• Repeat the procedure detailed in Activity 1, and observe colour changes to the bicarbonate indicators at the end of the experiment (figure 6).

Practical tip

To ensure fair testing, the amounts of bicarbonate indicator added to the bottle caps need to be the same.

Watch a demonstration of Activity 2a.

Part 3: Monitor the change of temperature

• Calibrate the temperature sensors if necessary.
• Set up the experiment as for Activity 1. You can use the same candles but ensure the wicks are the same lengths and the glass jar is replaced to ensure the experiment starts at room temperature.
• Connect three temperature sensors and use Blu Tack or tape to stick the sensors at different levels inside the gas jar (figure 7).
• Repeat the procedure detailed in Activity 1, and collect data for temperature changes at different levels inside the gas jar (figure 8).

The results should show that the carbon dioxide levels and temperature rise more towards the top of the jar. Discuss with students whether these results support their explanations. Are there any alternative explanations that are consistent with the results?

Activity 3: Elaborating and evaluating student learning about the candle mystery

To assess students’ deep understanding and ability to apply their explanations, you can introduce variations of the candle experiment in different contexts. Challenge your students to consider what they think might happen if we place the candles in separate jars. [ 3 ] Additionally, ask them to explore the results if we introduce an electric fan into the setup. This can be combined with another think–pair–share activity to promote discussion and evaluate their understanding of the concepts. Allow 40 minutes for the experiments and discussion.

• Portable fan

Worksheet 3

• Activity 3 explanation

Part 1: Burning candles in individual beakers

• Ask the students what they think would happen if the candles were lit in individual jars. This can be done using the think–pair–share approach.
• Secure three candles of different heights to the bench (this also works with two candles).
• Light the candles and cover each with a separate beaker (figure 9).
• Record the time required for each candle to go out.
• Repeat the experiment to get more reliable data.

To ensure fair testing, the volume inside the beaker must remain the same throughout the experiment. If a candle needs to be cut, the cut pieces should be placed inside the beaker.

Watch a demonstration of Activity 3a.

Part 2: Burning candles near a small fan

• Ask the students what they think would happen if a fan were placed in the jar. Place a portable fan near the three candles used in Activities 1 and 2, and turn the fan on.
• Repeat the procedure detailed in Activity 1, and record the time that the candle goes out.
• Repeat the experiment with the fan turned off.
• Compare the time taken for the candle to go out when the fan is on and off.

Practical tips

• To ensure fair testing, the volume inside the beaker must remain the same throughout the experiment. The electric fan should be placed inside the beaker, whether it is turned on or off.
• To repeat the experiment, you may fan the gas jar to restore it to room temperature and avoid the build-up of CO 2 , or you can use a new gas jar.

Watch a demonstration of Activity 3b.

The candles go out at similar times in the experimental setups with separate beakers or with an additional electric fan. The results contrast the experimental results in Activities 1 and 2. To ensure reliability of the results, students are encouraged to repeat their experiments, which can be performed within 5 minutes. Encourage students to provide explanations for their observations. Students are asked to construct explanations of how and why things happen in the setup using their explanations developed in Activity 2. You may give groups the model answer ( Activity 3 explanation ) at the end to compare it to their descriptions.

The activities based on simple twists to the classic candle experiment can serve to improve students’ abilities to develop, revise, and apply scientific explanations, as well as to explore scientific skills such as control of variables, hypothesis testing, and coordinating multiple pieces of evidence. As an extension activity, you could encourage students to handle quantitative data in an in-depth discussion and demonstrate their learning through report writing and group presentation. The process of predicting and explaining different unfamiliar contexts can help create valuable teachable moments that motivate students to learn.

[1] Bybee RW (2015) The BSCS 5E Instructional Model: Creating Teachable Moments . National Science Teachers Association Press. ISBN-10: 194131600X

[2] Cheng MW (2006) Learning from students’ performance in chemistry-related questions. In Yung BHW (ed.) Learning from TIMSS: Implications for Teaching and Learning Science at the Junior Secondary Level pp 51–74. Education and Manpower Bureau.

[3] Details for how to investigate candle burning: https://edu.rsc.org/resources/candle-burning-investigation-planning-an-experiment/619.article

• Watch demonstration videos of the experiments in Activities 1 ( candle mystery ), 2 ( CO 2 concentration ), and 3 ( individual beakers and electric fan ).
• Learn how to make convection currents visible using mist: Lim ZH, Shu A, Ng YH (2023) A misty way to see convection currents . Science in School 64 .
• Explore the nature of science by investigating a mystery box without peeking inside: Kranjc Horvat A et al. (2022) The mystery box challenge: explore the nature of science . Science in School 59 .
• Try some experiments with gases to illustrate stoichiometric reactions and combustion: Paternotte I, Wilock P (2022) Playing with fire: stoichiometric reactions and gas combustion . Science in School 59 .
• Learn about data visualization by sketching graphs from ‘story’ videos of everyday events: Reuterswärd E (2022) Graphing stories . Science in School 58 .
• Read about the environmental costs of fireworks: Le Guillou I (2021) The dark side of fireworks . Science in School 55 .

Steven Ka Kit Yu has been working in the education sector in teaching, research, and administrative roles. He was a secondary science teacher and a part-time lecturer in the Faculty of Education, the University of Hong Kong.

Supporting materials

Activity 3 Explanation

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To demonstrate features of the burning process and to debunk myths about this supposedly well-known demonstration.

Burning candle apparatus with colored water.

Description

A common pre-college experiment is to burn a candle inside of a bottle which has been turned upside down over a container of water. The water supposedly rises about one-fifth of the way up the bottle, indicating that the oxygen, about one-fifth of the air in the atmosphere, has been "used up" in the combustion process. The candle in our experiment is placed inside the sealed tube containing air above a colored water bath, and is then ignited by a hot wire. The water level goes down initially, then returns to its original level just after the candle goes out. There is NO CHANGE in the water lev

Lecture Demonstration Formula Sheet. John H. Rosengren, Old Experiment - New Twist, Elementary School Science Bulletin,nationa Science Teachers Association, November 1962, pages 10-11.

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Playing With Rain

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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.

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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.

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!

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.

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

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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

Not the answer you're looking for? Browse other questions tagged water home-experiment physical-chemistry or ask your own question .

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NOTIFICATIONS

The great candle experiment.

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In this activity, students cover a lit candle with an inverted jar in a saucer of water. The flame expires and the water rises up in the jar.

By the end of this activity, students should be able to:

• engage in scientific debate, using observation to present ideas
• understand the effects of heat in terms of expansion and contraction in this experiment.

Download the Word file (see link below) for:

• introduction/background notes
• what you need
• discussion questions
• scientific explanation
• student instructions.

Nature of science

Explanations of observations can be tricky. Scientists need to be careful that their prior knowledge doesn’t lead to plausible explanations that actually turn out to be incorrect – or not the whole reason why something might happen.

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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!

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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.

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

The smokey effect is pretty cool.

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!

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Experiment #1

A candle flame is actually a chemical reaction in action! Candle wax is one of the chemicals in the reaction. Can you guess what the wax reacts with? Find out in this experiment!

1. Ask the adult you are working with to light the candle.

2. Watch the candle flame start out small and get bigger. Notice how some of the wax near the wick melts.

3. As the flame burns, the wax from the candle is reacting with something else to make the flame. 

What do you think it might be?

4. Ask the adult you are working with to carefully place a glass jar over the candle and to leave it there.

 What to expect 

The flame will go out.

What’s happening in there?

Why does the flame go out when the jar is covering it?

The substance that reacts with the candle wax is oxygen. It comes from the air. Putting the jar over the candle keeps oxygen from outside the jar from getting in.  The reaction can only use the oxygen that is already in the jar. So, when that oxygen is used up, the reaction can’t keep going. Running out of oxygen makes the flame go out.

Experiment #2

Another chemical reaction you probably know is the reaction between vinegar and baking soda. This reaction produces a gas called carbon dioxide. This gas can be used to put out a flame. Let’s try it!

1. Ask the adult you are working with to light the tealight candle.

2. Place about two teaspoons of baking soda in the jar.

3. Next pour about two tablespoons of vinegar in a cup.

4. When you are ready, carefully pour all the vinegar from the cup into the jar with the baking soda.

5. Hold your hand gently over the top to keep most of the carbon dioxide in the jar.

6. Ask the adult you are working with to carefully pour the carbon dioxide gas onto the flame. Be sure no liquid comes out – just the gas.

 What to expect?

The flame should go out.

Why does the flame go out when carbon dioxide is poured on it?

Carbon dioxide molecules are heavier than air. Because of this, they push the oxygen and other molecules in the air out of the way as they sink down over the flame and candle. When oxygen is pushed away from the wick, it can’t react with the wax anymore. This makes the flame go out.

Next time you blow out a candle, think about what your breath is actually doing. Why do you think blowing on a candle flame makes it go out?

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