What happens when fire burns up oxygen

We have been looking at how fire burns. This is a neat experiment but needs to be done with a grown-up.

You need
- Candle and matches
- container
- glass jar
- Water
- Food colouring

What to do:

1. Add enough water to fill the bottom of the container.

2. Put 3 or 4 drops of your favourite colour of food colouring into the water and mix it up.

3. Place the candle in the middle of the container. (We used blutac to stick it down)

4. Light the candle.

5. Take the glass jar and place it over the lit candle.

 What happens to the water level inside the glass? What happens to the flame on the
candle?


What’s going on:

The flame on the candle needs the gas oxygen to keep burning. Once we place the glass
container over the lit candle, the oxygen inside begins to get used up. Once all the oxygen has
been used, the flame will go out. However, there are still other gases remaining inside the
glass (nitrogen, argon, carbon dioxide, etc). But these gases have lower pressure inside the
glass when compared to the higher atmospheric pressure on the outside of the glass.  This
higher atmospheric pressure from the outside pushes the water from the plate up and into the
glass.

http://www.weirdsciencekids.com/whydoesthewaterrise.html