A Candle Needs Air to Burn

We know that plants need air, water, soil and heat to grow.

We know that humans need food, water, exercise, fresh air and sleep to live.

We think that a candle needs air to burn.

We tried this out with teacher’s help (we always get an adult toTe help when we use matches or hot water).

Teacher lit a candle.  Then she put a glass over the candle.  We know that the glass was full of air even though we can’t see it.

The candle continued to light for a while, and then it went out.  We are pretty sure this is because there wasn’t any more air in the glass for the candle to use.

Then this experiment got really interesting.  Teacher put the candle floating in a shallow bowl of water.  She put yellow food dye in the bowl just so we could see the water more easily.

We predicted what would happen to the candle this time.

Again the candle was lit, again the glass was placed over the candle, again the flame went out after just a little while.  No surprise there.

But then teacher got a volunteer to very gently lift the glass.  The bowl lifted too.  We really didn’t expect this!

We know this is because a vacuum is made when all the air is used up.  This vacuum tries to suck the bowl into the glass.  Well, it can’t be sucked into the glass, but there is a strong seal made between the glass and the bottom of the bowl.  It is this suction that allows the glass to be lifted.  If we break the seal, the water rushes in to the glass, and we can see exactly how much air the candle used up when it was burning!