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INV. 6 (PART 2)

INV. 6 (PART 2). EVAPORATION AND HUMIDITY. REVIEW OF PART 1 . Explain to your shoulder partner what your group did in part 1 to prove water vapor is in the air. Share whole class: How do we know that in fact there is water vapor in the air?. Water Vapor.

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INV. 6 (PART 2)

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  1. INV. 6 (PART 2) EVAPORATION AND HUMIDITY

  2. REVIEW OF PART 1 • Explain to your shoulder partner what your group did in part 1 to prove water vapor is in the air. • Share whole class: How do we know that in fact there is water vapor in the air?

  3. Water Vapor • With your shoulder partner, discuss: Do these pictures provide good evidence for water vapor in the air? Could there be another explanation? • Think: How does water vapor get into the air?

  4. EVAPORATION • Write the following definition in your notebook. • Evaporation - The PROCESS by which LIQUID WATER becomes a GAS called WATER VAPOR.

  5. Water in the Air? • Gently blow on the spot on your left hand to simulate wind. • Tell your shoulder partner why you think your hand feels cold. Dampen a small area on the back of both hands Fill a cup half full of water

  6. Why? Heat is required to evaporate water Energy transfers from hand to water by conduction. Reduced heat = cold signal to your brain

  7. QUESTIONS (WIND) • Think: What effect does wind have on the wet spot? • Think: Where did the water go that was on your hands? • Discuss with shoulder partner: How is this similar to the weather?

  8. Procedure • For each pair: • Two thermometers • Two pieces of fabric • Two rubber bands • Paper towel • Double tables will share the cup of water • Think and Discuss: How could you use the materials to measure temperature change during evaporation?

  9. Starting temperature • What is the starting temperature of your thermometer?

  10. Procedure (con’t) • Wrap a piece of muslin around the bulb end of your thermometers securing with rubber bands • Dip the muslin end of 1 thermometer into the water blotting excess water

  11. Procedure (con’t) • How can you increase the amount of evaporation from the fabric? • Waving the fabric back and forth rapidly • Wave your wrist back and forth • Take turns • Will shake for 1minutes and then 5 minutes • Record data in a table

  12. TABLE

  13. Results • Think: What happened to the water on the fabric? • Think: What caused the temperature to go down? • Remember: • Evaporation (liquid to vapor) requires energy • Energy = heat in the environment

  14. Discuss Results • What happened to the water on the fabric when you waved the thermometer around in the air? • Water evaporated • When water evaporates from a surface, what happens to the amount of water vapor in the air? • It increases

  15. DISCUSSION CONT. • What is required for evaporation to happen? • Where did the heat come from? • When you take heat energy away from an object, does the object get warmer or colder?

  16. DISCUSSION CONT. • So, if evaporation requires heat energy— • Where did the energy come from? • When energy transfers from an object, does the object get warmer or cooler?

  17. Vocabulary • Water vapor is the gaseous phase of water • Evaporation is when liquid water changes from a liquid to gas (water vapor) • Humidity is watervapor in the air • When it is humid = there is more water vapor in the air

  18. Saturated • When the air contains as much water vapor as it can Only a little bit of water vapor to saturate cold air Takes a lot of water vapor to saturate warm air

  19. Relative Humidity • How meteorologist often describe the amount of water vapor in the air • Measured in percentages (%). • Compares the amount of water vapor in the air to the amount needed to saturate the air

  20. Relative Humidity = 100% The air is saturated with water vapor Air can’t absorb any more water No evaporation occurs

  21. Into the Air • Water vapor gets into the air several ways • Liquid water can evaporate when it absorbs energy (radiation and conduction) • Transpiration : water vapor given off from vegetation • All terrestrial animals breath out vapor • Fires • Volcanic eruptions

  22. Hygrometer • Measure relative humidity • Measures the water vapor in the air and compares that to the amount needed to saturate the air • Relative Humidity as a percent

  23. Calculating Relative Humidity • Use lab pages 31/33 • Record thorough notes with teacher using examples on lab page 31 • Work as tables to complete the rest of the sheet. • Complete side 2 (pg. 33) together.

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