Making your own simple thermometer.

You will need
a) a strong plastic bottle with a scew cap
b) a thin plastic straw
c) some modelling clay
d) a sellotape; and
e) some water coloured with poster paint.

Steps

1. Ask an adult to drill a hole in the bottle's cap. Assemble the thermometer, making sure that the water comes part way up the straw when you fix on the cap. Leave the water to settle for an hour then mark the water level on the scale.

2. Stand the thermometer in a bowl of ice cold water and a bowl of very hot water. See how the water level changes.