If liquid water evaporates in an open jar and then the jar is sealed in a refrigerator, what happens to the relative humidity inside the jar?

If liquid water evaporates in an open jar and then the jar is sealed in a refrigerator, what happens to the relative humidity inside the jar?

• A. Decreases
• B. Increases
• C. Stays the same
• D. Decreases to zero

Answer: (B)

Relative humidity is a measure of how much water vapor is in the air compared to how much the air can hold at a given temperature. When the jar is open, water keeps evaporating into the air until the air in the jar becomes fairly humid at room temperature. Then you seal the jar and put it in the refrigerator, which lowers the air temperature inside. Cooler air can’t hold as much water vapor, but the amount of vapor trapped inside hasn’t changed. That mismatch means the relative humidity rises. If it cools enough, the air becomes saturated and water may condense on the inner surfaces. So the humidity inside increases.

Relative humidity is a measure of how much water vapor is in the air compared to how much the air can hold at a given temperature. When the jar is open, water keeps evaporating into the air until the air in the jar becomes fairly humid at room temperature. Then you seal the jar and put it in the refrigerator, which lowers the air temperature inside. Cooler air can’t hold as much water vapor, but the amount of vapor trapped inside hasn’t changed. That mismatch means the relative humidity rises. If it cools enough, the air becomes saturated and water may condense on the inner surfaces. So the humidity inside increases.