Period+3+Group+7

Response to Investigation 6 Essential Question(s)**
 * Period 3 Group 7


 * How can we determine that water vapor is in the air and how does it get there? What is humidity and what is dew point and how are each measured? How do clouds and dew form?**

We can determine that water vapor is in the air by making it condense onto something. It gets into the air through evaporation. We made water vapor condense during the lab we performed in class. In the lab we put colored ice into a bag and then sealed the bag. The water vapor gave its molecular motion to the bag, which transfered it to the ice. The molecules in the water vapor slowed down and the water vapor returned to a liquid form and condensed onto the bag. We know that water vapor gets into the air through evaporation because of the wet and dry thermometer lab we did. In the lab we wrapped wet fabric on one thermometer and dry fabric on the other. We waved both thermometers in the air for the same amount of time. The fabric on the wet thermometer gained molecular motion and the water changed back into a gas, taking the heat energy with it. We know the water evaporated because the temperature of the wet fabric decreased and the temperature of the dry fabric stayed about the same.

Humidity is the amount of water vapor in the air. It is measured with a hygrometer and recorded as a percent. We know what humidity is from the "Dragon's Breath" article. In the article, it explains that the amount of water vapor in the air will vary, and that it is called humidity. Relative humidity is how humidity in the air is measured. We learned that relative humidity is measured with a hygrometer from "Packet 21." In the packet, it says that the tool used to measure humidity is a hygrometer, but it used to be a psychrometer. The hygrometer shows the relative humidity as a percent.

Dew point is the temperature at which air is saturated. It is measured with a thermometer and recorded in degrees Celsius. It can also be measured by using charts that are provided by scientists. We know this because we performed and analyzed a dew point and condensation lab in class. From this lab, we learned that condensation is related to dew point. This creates a connection, because if the temperature of the air is at or below dew point, condensation forms. This is why dew point is measured as a temperature. The dew point must be hit in order for extra water vapor to condense, therefore dew point is when the air is saturated.

Clouds can form when water vapor condenses to condensation nuclei, and dew forms when water vapor condenses onto a surface like a blade of grass. We know how clouds form because we did an experiment in class with a soda bottle. There are multiple steps required to form a cloud. The first is that the sun gives its energy to the Earth's surface. After that, the water vapor evaporates and rises. The higher air cools, reaches dew point, and condenses onto condensation nuclei in the air. Millions of the nuclei combine to form a visible cloud. We know how dew forms because in class we analyzed a condensation lab.

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