Did you know candles were once used to tell time before mechanical clocks were invented? It’s true! And that birthday candle you blow out every year? It symbolizes the light of life, and when you make a wish, the smoke is said to carry that wish up into the air. So magical, right?
Today, we’re diving into a super cool candle science experiment for kids that teaches us all about air pressure, and how fire actually burns — all in one hands-on, mesmerizing activity.
This experiment is right out of my Birthday School Family Unit Study. Learn about fun birthday games, some delicious (and maybe not-so-delicious!) birthday foods, make a colorful present, and so much more with this hands-on unit that’s packed with birthday fun! It is available on its own or as part of the Celebrations Bundle.
Let’s dive into this fiery (but safe!) little science trick that’s guaranteed to spark your child’s curiosity.
Candle Science Experiment for Kids
I love doing science experiments with my children; we are learning and having so much fun in the process. Let’s get started!
Supplies
For this candle science experiment, you will need the following materials:
- Shallow dish
- Tealight candle
- Glass jar (like a mason jar)
- Water
- A lighter or a match
- Food coloring (optional – just for fun!)
Directions
To get started, fill up your shallow dish to about half full of water. If you’d like to make things a little more colorful, add a few drops of food coloring to the water. Then, place a tealight candle in the centre of the dish and gently float it on the water’s surface. Carefully light the candle using a lighter or match, and now you’re ready for the real magic.
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Take your glass jar and slowly place it upside down over the lit candle. As the jar traps the flame, ask your child what they think will happen. You’ll quickly notice the candle’s flame flickers and eventually goes out. But right after that — surprise! — the water in the dish begins to rise inside the jar, lifting the candle up with it. It’s a show-stopping moment that always earns a “whoa!” My kids were very excited, all wanting to try it again. When lifting the jar back up, it was fun to feel the vacuum created by the pressure of the cooling air.
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Once we tried re-lighting the candle a few times, I finally asked ‘So what’s really going on here?’ And we got to do some research.
This experiment is a simple and fascinating way to explore the science of fire and air pressure. A candle needs three things to burn: heat (from the match or lighter), fuel (the wax and wick), and oxygen (from the air around us). When you place the jar over the flame, it starts using up the limited oxygen trapped inside. Once that oxygen is gone, the candle can’t keep burning — so the flame goes out.
While burning, the candle heats the air inside the jar, making it expand. You might even see bubbles escaping as the hot air pushes out. But once the flame dies, the air quickly cools and contracts, lowering the pressure inside the jar. The higher outside air pressure then pushes the water up into the jar to balance things out — a process called equilibrium. Pretty amazing, right?
Extension Activity
Does the size of the jar affect how much water is drawn into it? What about the size of the candle? Try this experiment again, changing one of these components. Encourage your child to make predictions, observe carefully, and draw conclusions. This is how real scientists work!
Celebrations Family Unit Study Bundle
Keep that fun, hands-on learning and crafting going all year long with the Celebration Family Unit Study Bundle! Grab your copy and start today:
https://shop.tstest18.techsurgeons.com/products/celebrations-bundle
Thank you for reading, my friend!
xo
Sarah
