Science - Lesson 30
Heat
-Get Ready
A cold treat is great on a hot day. But the treat won't last long. Look at the picture. What do you think makes this ice cream lose its shape? Tell your ideas to a partner.
-Read to Learn
How can heat change matter?
Energy can make matter move or change. One kind of energy is heat. Heat can change matter from one state to another. Taking away heat can change a liquid to a solid. Adding heat can change a liquid to a gas. These changes are physical changes.
1. Water takes the shape of its container.
2. The tray is put in the freezer. The liquid will change to a solid state. The plastic tray will not change.
3. The solid ice cubes are placed in a pan and left at room temperature.
4. Heat causes the solid ice to melt, or become liquid.
5. The water returns to a liquid state.
6. When the water gets very hot, it boils. Then the liquid becomes a gas.
How can we use heat?
Much of our heat is from the Sun. The Sun warms Earth's land, air, and water. Without the Sun, Earth would be too cold for things to live.
Fire gives off heat. To do this, it burns fuel. Wood, natural gas, and oil are fuels.
Heat can come from electricity, too. We can use dams on rivers to make electricity.
You can rub your hands to make heat. Then you can hold a pencil. The heat moves from your hand to the pencil. Heat can move from one object to another. Heat moves through metal quickly. That is why people use metal pans when they cook.
Heat can change things. When a potter puts clay in a special oven, it changes. It becomes very hard.