WATER IN THE AIR

Investigation 6- Water in the Air Enduring Understanding: Humidity is the water vapor in the air Learning Goals: I will use ice water to cool air to produce condensation. I will measure changes in temperature due to evaporation. I will determine dew point by cooling water in a container until condensation occurs on the container. I will observe changes in temperature due to pressure change. I will use pressure to produce a cloud in a bottle. I will explain how dew and clouds form when humid air cools to its due point and condenses. I will predict could formation by analyzing radiosound sound data.

Condensation Hey you! Remember when you put water on your hand and then blew on it? It felt COLDER right? Why????

Question Time Condensation doesn’t occur all the time, just when there is a cold surface. Is there a temperature at which condensation starts to happen? Will condensation take place at any temperature if you allow enough time for energy transfer to occur?

Dew Point Some people refer to the condensation on a cold glass as dew. When and where can you find dew outside? How does dew form?

Dew Point The temperature at which water changes from gas to liquid – the temperature you found earlier – is the dew point. Dew point is the temperature at which air is saturated. Dew point is not the same everywhere, so you always have to figure out the dew point for the area you are interested in at the time.

More Dew Point Dew point depends on the amount of water vapor in the air. If a lot of water vapor is in the air, you don’t have to lower its temperature much to reach saturation. If very little water vapor is in the air, however, it must be cooled to a very low temperature for saturation to take place.

WORD BANK Dew Point= the temperature at which water changes from a gas to a liquid

Dew Point Questions If you wait a moment or two, you will have some questions to answer. I am feeling nice, you may work: By yourself With ONE partner With TWO partners

WATER IN THE AIR

Investigation 6- Water in the Air Enduring Understanding: Humidity is the water vapor in the air Learning Goals: I will use ice water to cool air to produce condensation. I will measure changes in temperature due to evaporation. I will determine dew point by cooling water in a container until condensation occurs on the container. I will observe changes in temperature due to pressure change. I will use pressure to produce a cloud in a bottle. I will explain how dew and clouds form when humid air cools to its due point and condenses. I will predict could formation by analyzing radiosound sound data.

Wet/Dry Bulb Thermometers One way relative humidity can be determined is by comparing the temperature of the air and the temperature of a piece of cloth. These are called taking dry-bulb and wet-bulb temperature readings. What happened when we wet the fabric on the wet-bulb thermometer and waved it in the air?

Hygrometer Meteorologists use hygrometers to measure relative humidity. This is our class hygrometer. It measures the water vapor in the air and compares that to the amount of water vapor needed to saturate the air. The hygrometer displays relative humidity as a percentage. If the relative humidity was 100%, do you think things would dry up very fast? Could evaporation occur?

Relative Humidity What are our temps? Wet – Dry - We can use data from the thermometers to calculate the humidity of the air in our room. Meteorologists have a chart to convert this information into a humidity reading. (page 79 in your green science book)

Mr. Yorke Science This is a friend of Mrs. Kerich’s. He is going to fill you in on Relative Humidity. Click on Picture

Reading Dragon’s Breath Pg. 34

WORD BANK Relative Humidity= the amount of water vapor in the air compared to the amount of water vapor needed to saturate the air at a given temperature - measured in a percentage