Sea ice

Requirements
You will need 1) an aquarium or similar 2) a lot of ice cubes and 3) a marker.

Procedure

1. Fill the aquarium approximately half with water
   
   
2. Put in the ice cubes (preferably many)
   
   
   
   
3. When the water has settled, the water level is marked with the marker on the outside of the aquarium.
   
   
   
   
4. When the ice has melted, the water level should be unchanged.
   

To save time you can run the three lab experiments as parallel activities and discuss them as time passes.