Experiment
The tip of the iceberg
Does ice sink or float in water? What happens to the water level when the ice melts?
Curriculum objectives - Science:
- explore the senses through play outside and inside and talk about how the senses are used to gather information
- wonder, explore and create questions, and link this to your own or others' experiences
You need:
- A large ice cube.
- A glass.
- Water.
This is what you do:
Place a large ice cube in a glass and fill with water until it is completely full, so full that it bulges slightly over the rim. The ice cube floats up and sticks even further up than both the surface of the water and the edge of the glass
Explore further:
- Make a hypothesis. Will the ice sink or float?
- Do you hear anything when you fill up with water?
- What happens to the ice cube?
- Let the glass stand for a few minutes. What happens when the ice cube melts? Does the water flow over the edge of the glass?
Explore further:
Try the same experiment with a glass of cold water and one of hot water.
- Which glass makes more noise when you fill it with water?
- In which glass does the ice melt the fastest?
What is going on?
The water does not overflow even if the ice cube sticks up above the surface of the water. The reason for that is that the ice cube only needs to get rid of as much water as it contains. It floats up because ice has a lower density (something about what density is? And why does frozen water have a lower density? "Have you noticed that water expands when it freezes?" or similar?) than liquid water. In the same way, the sea will not rise because of an iceberg melting.
This unique property of water is particularly beneficial for fish that live in bodies of water that freeze in winter. Because ice floats, the bodies of water freeze from top to bottom. This allows fish to survive deep underwater, even when the surface freezes!
