Clouds are formed as water evaporates from the Earth's surface and condenses in the atmosphere. Solar radiation evaporates water on land and in the oceans. The rising water vapor eventually encounters cooler air the higher it goes. This causes the vapor to cool and condense, or revert to a liquid state. Tiny droplets form and millions of these droplets form a cloud. Observe evaporation by putting two dishes with an equal amount of water in different places. Put one dish in the sun and one in the shade. The water will evaporate quicker from the dish in the sun.
Cloud droplets combine with each other to form bigger droplets. Big droplets fall to the ground as rain, starting the cycle again. Draw a model of how water evaporates into the air and falls down as rain. Focus on showing what happens in a cloud, where the water droplets get bigger and eventually are big enough to fall down as rain. Add different types of clouds. Clouds usually drift from their place of origin. The clouds farthest from the Earth's surface contain hail or snow.
Clouds are formed when cold and warm air meet. Cold air holds less water vapor than warm air, and when cold and warm air meet, part of the air condenses into rain or ice. The clouds provide clues about the weather that is coming. Dark clouds contain more water droplets, which means it is more likely to rain. Test condensation or cloud formation by using a mirror. Get close to the mirror and exhale your hot breath onto the mirror. Test different temperatures on the mirror by putting it briefly in a warm place or cold place, such as in the sun or in the fridge. You should see less condensation with a warm mirror.
Clouds need tiny particles to form. Dust, dirt and pollutants give the water molecules a surface where they can condense into water droplets. Lead in the air can influence the temperature at which clouds form. Lead particulate released into the air due to human activity means clouds can form at warmer temperatures and with less water. Lead is released into the air mostly by large-scale metal processing. Write a story about what happens in the cloud and how these changes could influence both rain and snow.