G3_Water and the Three States of Matter 400 – 500L_06

Look up into the sky. Do you see those clouds? There are clouds in the sky for the same reason there is dew on the grass. Warm, moist air rises and cools. There are also tiny pieces of dust floating in the air. They are cooler than the warmer, moist air. Can you guess what happens when they meet? That’s right! When they touch, condensation occurs. Water vapor is turned into liquid water.

In a cloud, the drops of water are tiny and light. The moving air is able to hold them up. What if these droplets start to combine? They will get larger and heavier.

Imagine a slightly moist sponge. You can hold it up and it doesn’t drip. What if you add even more water to the sponge? At some point it will start to drip. This is similar to what happens in clouds. When there is a lot of water, the droplets will get bigger and bigger. They will be too heavy for the moving air to hold them up. That is when we have rain. The drops of water fall to Earth.

Water on Earth is constantly changing its form or state. Water can change from a liquid to a gas when it is heated. This is called evaporation. Water can also change from a gas back into a liquid. This is called condensation. It can even change into a solid when temperatures are cold enough to freeze it. This is all part of what makes water so special.