Cloud Catchers: Finding the Dew Point and Making Clouds in a Jar
Science Lab · Grade 6 · ngss
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Type
science_lab
Pre Lab
Background: The air around you is full of water, even if you cannot see it. Water in the air exists as an invisible gas called **water vapor**. The amount of water vapor in the air is called **humidity**. Warm air can hold more water vapor than cold air. When air holds as much water vapor as it possibly can at its temperature, we say the air is **saturated**. Scientists often describe humidity using **relative humidity**, which compares how much water vapor is in the air to the most it could hold at that temperature, written as a percent.
When air cools down, it cannot hold as much water vapor. If air cools enough, it becomes saturated, and the water vapor begins to change from a gas back into tiny drops of liquid water. This change of state is called **condensation**. The temperature at which condensation begins is called the **dew point**. You have seen this happen when a cold drink 'sweats' on a hot day, or when grass is covered in dew on a cool morning. The water did not leak through the glass. It came from water vapor in the air that cooled when it touched the cold surface.
Clouds form the same way, but high in the sky. As warm, moist air rises, it expands and cools. When it cools to its dew point, water vapor condenses into billions of tiny droplets. But water vapor needs something to condense onto. Tiny particles of dust, smoke, sea salt, or pollen, called **condensation nuclei**, give water droplets a surface to form on. Billions of these droplets together make a **cloud**. In today's lab, you will measure the dew point of your classroom air and build a cloud in a jar.
Vocabulary
Term: Water vapor
Definition: Water in the form of an invisible gas.
Term: Humidity
Lab Type
Post Lab
Standards
Safety Level
Teacher Notes
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Experiment Design
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Learning Objectives
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