Ice is a solid but it floats on water. Why does solid ice float?

Let’s do a small activity to find out.

Pour water into a transparent glass container. Mark the level of water. Put it in the freezer.

When the water in the container has frozen, remove it from the freezer. Mark the level. You will find that it has crossed the level marked for water.

This shows that water on turning into solid ice occupies more space.
Ice takes up about 9% more space than it does as a liquid.

Because ice occupies more space than liquid water, ice is less dense than water. Density is mass in a given volume. Any substance which is less dense than water floats on water. Water is densest at 4 degrees centigrade.

In freezing weather conditions, water below the layer of ice remains a liquid. This unique property of water allows fish and other aquatic life to survive in harsh winter conditions and even in the North Pole