Warming, cooling and nature’s forces
Warming and cooling can change materials. Warm ice and it melts into water. Cool water in a freezer and it freezes into ice. A grown-up can heat water until it turns into steam. When steam touches something cold, it turns back into drops of water. An egg is different. When a grown-up cooks an egg, it changes for good. We cannot make it raw again. Fresh water is water that is not salty. The Nile is fresh water. We use it for drinking, washing and farms. Rain is rare in most of Egypt, so the Nile is very important. Wind and water also change the land. They carry away sand, soil and rock. This is erosion. Over a long time it can wear away a monument that stands outside.
| Change | Warm or cool? |
|---|---|
| ice to water | warm |
| water to ice | cool |
| water to steam | warm a lot |
| steam to water | cool |
Ice test with a grown-up. Put one ice cube in a cup in a warm, sunny place and another in a cup in the shade. Predict: which will melt first? Check every few minutes. Say what you see. Do not drink the water. Only a grown-up heats water or cooks.