What you do:

1. Get an adult to boil some water on the stove for a few minutes.
2. Pour the water into a smooth, round bowl.
3. Immediately put the water in the freezer, and wait until the water has frozen.
4. Remove the ice from the bowl (if you have trouble doing this, try heating the bottom of the bowl with warm tapwater.)
5. You have made a giant magnifying glass out of ice that you can use to concentrate the sun’s rays! Try reading words written on paper or looking at small objects. Make sure that an adult is there to help you while you experiment with your magnifying lens.

What happened?

When light is passed through ice, it slows down a tiny bit, and the ice causes the light to bend. The bending of light is called refraction. Convex lenses, which are lenses that curve outward like a magnifying glass, cause light to bend inward. All the light rays passing through the ice will meet at one point, which will become very bright and very hot. Although the sun’s rays are passing through ice, they are only cooled an unnoticeable amount as they do.

So why boil the water first?

Fresh water often contains lots of air, which turns into bubbles as the water freezes and clouds up the ice. But boiled water has very little air in it, so the magnifying lens you create is clear ice.