Lesson 45: Clouds and Weather
Clouds contain liquid droplets, ice crystals, or both. Cooling, rising air, condensation, and fronts help explain cloud formation and precipitation, alongside the difference between weather and climate.
Key Ideas
- Clouds are made of tiny water droplets, ice crystals, or both. Water vapor is an invisible gas. Fog is a cloud near the ground.
- When moist air cools enough, some water vapor can change into droplets. Rising air often cools, and fog can form as air cools near the ground.
- Tiny cloud droplets and ice crystals settle very slowly. As they grow larger, they can fall as rain or snow.
- Air masses can meet at a front, where air may be lifted to form clouds or rain. Weather can also develop locally.
- Weather is what conditions are like now. Climate describes weather patterns over many years.
Vocabulary
- Water Vapor / Condensation: Water vapor is water as an invisible gas. Condensation changes it into liquid droplets.
- Cumulus: Puffy, heaped clouds often formed by rising air.
- Stratus / Cirrus: Stratus forms low layers. Cirrus forms high, wispy clouds mainly made of ice.
- Air Mass: A large amount of air with similar temperature and moisture throughout.
- Front: A boundary where air masses with different temperatures or moisture meet.
- Weather / Climate: Weather is what the air and sky are like now. Climate is the pattern of weather over many years.
Discussion Questions
- Fog often shows up early in the morning and burns off by mid-morning. Using what you know about warm air and cold air, explain both halves of that.
- Mountains can force moist air upward. How could that produce clouds on one side and drier air on the other?
- A forecast says forty percent chance of rain. What do you think that number actually means, and why would a forecaster give a number instead of a yes or no?
Supplies
- A clear jar with a lid, warm water, a plate of ice cubes, a match, and an adult to handle the hot water and the match
- A notebook, two minutes a day, and the same time each day