Incredible Burning Candle in Water Experiment (Free Worksheet)

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

My son did this experiment for the first time when he was six, and by his reaction, you would think I just pulled off a magic trick. He watched the water creep up inside the glass, grabbed my arm, and whispered, “Mom. How is it doing that?”

That’s the thing about the burning candle in water experiment. It looks like a trick even when you know exactly what’s happening. And the explanation is actually pretty cool science.

You only need a few things from your kitchen, it takes about ten minutes, and I’ve included a free worksheet so your kid can record their hypothesis and observations like a real scientist. Grab it at the bottom of this post.

Burning Candle in Water Science Experiment

Note: Adult supervision required – this experiment uses an open flame.

Materials: 

• A plate with a raised rim or a shallow bowl
• Water
• Candle
• 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, about 1 cm deep.

5. Light the candle with a lighter or match.

If you’re using the free worksheet, have your child draw their prediction of what will happen before you place the glass over the candle.

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

7. Watch what happens while the flame is still burning – and then watch what happens when it goes out.

Did your kid’s jaw drop? Mine loved watching the sudden rise in water level so much that we did this over and over until the candle wouldn’t light anymore.

Have your child write or draw their observations in the worksheet before you explain the science. Getting their hypothesis down first makes the explanation land so much better.

Why Does Water Rise When You Put a Glass Over a Candle?

When you place a glass over a lit candle sitting in water, two things happen. The burning flame consumes the oxygen inside the glass, and the heat warms the trapped air, causing it to expand slightly and escape as tiny bubbles beneath the rim. When the flame goes out, the air cools rapidly and contracts. This lowers the air pressure inside the glass below the air pressure outside, so the higher-pressure air outside pushes down on the water in the dish, forcing it up into the glass until the pressure equalizes.

Here’s the step-by-step of what’s actually happening:

While the candle is burning: The flame heats the air inside the glass. Hot air expands, creating higher air pressure inside than outside. Some of that pressurized air escapes as tiny bubbles from under the rim – you may see them if you watch closely.

When the flame goes out: The candle runs out of oxygen and extinguishes. The air inside the glass cools quickly. Cooling air contracts, which lowers the air pressure inside the glass below the outside air pressure. The higher-pressure air outside pushes down on the water in the dish, forcing it up into the glass until the pressure equalizes.

That’s why the water rises – not magic, just air pressure.

For a different take on the same concept, the balloon in a jar experiment uses the same air pressure principle with a dramatically different (and equally jaw-dropping) result.

Science Extensions to Try

This is where the experiment gets really fun. Once your kid has seen it work once, they’ll want to test everything. Here are some good variables to explore:

• Use hot water or cold water instead of room temperature water. Does the temperature of the water affect how high it rises?
• Try a larger candle versus a smaller one. Does the size of the flame matter?
• Use multiple candles. Does more flame mean more water?
• Swap the water for a different liquid, like vinegar or milk. Does the type of liquid change the outcome?
• Use more or less water in the plate. Does the starting water level affect the result?
• Try different sizes of glasses. Does a bigger glass change how much water rises?
• Try a glass with a narrower neck. What do you notice?

For a no-flame version of the same concept, try the hot and cold balloon experiment – it shows how temperature changes air volume using just a balloon and a bowl of water.

Free Rising Water Experiment Worksheet

If your kid is the type who always wants to know why (mine never stops asking), the free worksheet turns this into a proper science activity. There’s space to draw a prediction before you start, record observations during the experiment, and write a conclusion at the end.

It’s great for homeschool science journals or just for keeping little hands busy while the candle does its thing.

Final Thoughts on the Burning Candle Rising Water Experiment?

If your kid wants to repeat the experiment and the candle keeps going out immediately, the air inside the glass is still depleted of oxygen. Blow into the glass, wave it around for a few seconds to refresh the air, then try again.

I hope your kid is as amazed by this one as mine was. And if you try the worksheet, let me know how the hypothesis-writing goes!

Looking for more experiments like this one? We have a whole collection of easy science experiments for kids at home that use supplies you already have.

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