How Clouds Form

In the experiment described at the beginning of the video, what two main processes are represented by the hot water turning into invisible vapor and then the vapor cooling to form tiny droplets on the upper cup?

• Precipitation and sublimation

• melting and freezing

• evaporation and condensation

• runoff and transpiration

During the process of evaporation, the sun heats up water bodies, turning water into invisible water vapor. Why does this water vapor travel upward and rise high into the atmosphere?

• because the atmosphere pulls the vapor upward with gravity

• because it is pushed up by cold air currents

• because water vapor is lighter, or less dense, than air

• because it is seeking out strong winds

After water vapor rises high into the atmosphere, why is the process of condensation triggered?

• the vapor collides with strong winds, causing it to slow down

• the air in the higher layers of the atmosphere is much cooler than the air at the surface

• water vapor becomes heavier the higher it travels, pulling itself downward

• the particles of dust and pollen attract the vapor, heating it up

Which of the following best describes the process of condensation that is necessary for cloud formation?

• the process by which water droplets are converted into invisible water vapor

• the conversion of water vapor into water droplets

• the clustering of tiny particles like dust and pollen together

• the merging of large water droplets until they trickle down as rain

When warm water vapor reaches the cooler, higher layers of the atmosphere, it cools down and undergoes condensation. What tiny particles must the water vapor cling onto to successfully form tiny water droplets?

• salt crystals

• dust or pollen

• carbon dioxide molecules

• oxygen and nitrogen

As more and more droplets gather together, a cloud grows bigger and denser. What happens to the cloud's appearance when it becomes heavy enough to eventually form a rain cloud?

• it becomes wispy and feather-like

• it becomes fluffy, white, and cotton-like

• it becomes darker and heavier

• it becomes completely invisible