Water in a cup sloshes around if you don’t move it carefully. What about fire? Let’s find out!
Safety: This activity involves fire, so ask an adult to help. Don’t do this activity during a fire ban.
First aid: If you burn yourself, blow out the candle and run the burn under cold water for 20 minutes.
When I did this activity, I found the flame moved in the same direction as the jar! That’s exactly the opposite of what I expected to happen.
Imagine the jar is half full of water. When you move it fast, the water will move to the back of the jar. (You can even try this out to make sure!) So why does the flame go the other way?
Inside the jar there is a candle with a flame. But there’s also something else you might not think of: air.
Air doesn’t weigh a lot, but neither does a flame. In fact, air is denser (has more weight packed into its volume) than flames. That’s why flames point upwards.
When you move the jar, the air moves to the back of the jar. The lighter flame floats on top of invisible air, and gets pushed the other way. That’s why the flame moves forward, the same way you push the jar!
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3 November, 2018 at 9:38 am
Hey David
I really like this activity and am going to use it with my year 8 Science class as we are learning about energy
Thank you 🙂
5 November, 2018 at 9:22 am
Yay! It’s more of a buoyancy activity really, but it might help if you’re trying to understand exactly what fire is. Although I still don’t really understand what fire is…
Hope you’re doing well!