Words to Know

• Condensation - The process by which molecules of water vapor become liquid air.
• Evaporation - The process by which water molecules in liquid water escape into the air as water vapor.
• Nuclei - The central and most important part of an object; for this lesson, it is a cloud.
• Opaque - Not able to be seen through; not transparent.
• Tropopause - The boundary between the troposphere (where all weather occurs) and the stratosphere (the layer of ozone that protects the Earth from UV radiation).