"Ice in water and alcohol" Return to list of pracs

Aim: This activity is used to investigate how density affects floating.

Equipment: The equipment includes...  

Method: Set up one a glass with water in it and another with methylated spirits in it. Place a piece of ice in the water and note that it floats. Place a piece of ice in the glass of methylated spirits and note that it sinks.

Background knowledge: The density of water is greater than ice: in English this means that there is more weight packed into the same area. Ice will therefore float in water. The density of alcohol (methylated spirits - ethanol) is less than ice: therefore the ice will sink. Ice is one of the only substances that actually expands (or increases in size) when you place water in a freezer and it becomes ice. This is why you should never freeze drinks in glass bottles because it is likely to smash the bottle!

This fact is very useful for sea life ... when winter comes over in very cold climates in the world where rivers and lakes begin to freeze over then ice being less dense than water will form on the surface of the water. This acts to insulate life underneath. If it froze on the bottom of the lake, all the plankton and plant life will die and as a result all other sea life that depends on this will die. It will therefore cause all sea life to be severely affected.