What You Need:
- A porous rock like pumice stone (available at a chemist)
- A balance that can weigh units of 1gm or less
- Containers - 2
- Weigh the dry rock and chalk and record their weights.
- Fill the containers with water. Put the rock in one container and the chalk in the other. Leave it there for at least an hour.
- Take the rock and chalk out. Shake off the excess water. Weigh them again and record their weights.
- Weigh and record several other times at one hour intervals.
- Leave the objects in water overnight. Weigh and record their weights again.
Both the chalk and the rock will weigh more than their dry weight. The amount of water the rock can hold can be measured using the displacement method. In this case:
Weight of dry rock: 34gms
Weight of rock after 24 hours in water: 37gms
Total water absorbed by rock: 3gms or 3cc
Water level in the container: 150ml
Water level in the container after placing the rock: 175ml
Volume of the rock: 25ml or 25cc.
To calculate the quantity of water the stone can hold in percentage volume: Volume of water absorbed/Volume of stone = 3cc/25cc = 12%