Speedy Science: hot and cold

This experiment was messy so do it somewhere it is easy to mop up the water, we used the bathroom, outside would work too.

What you need:

• 2 identical jars
• a piece of card big enough to cover the top of the jar
• a jug of cold water, coloured with food colour, blue
• a jug of hot water, coloured with food colour, red (slightly hotter than bath water)

1. Fill the first jar with the blue cold water.

2. Fill the second jar with the red hot water.

3. Place the card on the jar of hot water.

4. This is the tricky bit... hold the card and carefully tip the jar and card upside down...

5. Place the jar on top of the cold water jar, make sure the mouths of the jars are aligned. Then carefully remove the card...

6. Taa-daaa the colours don't mix!

7. But wait! What happens if you do it the other way around? Repeat the exercise but this time with the cold water on top, what happens?

I must admit, we had a couple of hiccups doing this and didn't quite get the jars aligned, good job we were doing it in the bathroom! Fun trick though.

The science...

Liquids of a higher density will sit beneath those of a lower density. Therefore this proves that hot water has a lower density to cold water. This is because the molecules in hot water are moving faster than the cold water molecules, which creates more space around them thereby reducing the density.

Don't forget to share the post if you think your friends would like to dye their bathroom floors purple too...