Answers to the Relative Humidity Gizmos Lab PDF

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Your welcome :) sooo i hope you pass and get a 100 on your work bye have a great day!!!!! I am uploading this because I feel bad for you. All of this is right btw I got a 100....

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Name: Brenda Vasquez Romero

Relative Humidity Define Vocabulary: 1. Condense: to change from a gas to a liquid 2. dew point: the temperature at which water vapor will condense onto a moist surface as fast as it evaporates from it. 3. evaporate:to change from a liquid to a gas. 4. humidity: the amount of water vapor in the air 5. psychrometer: a tool used to measure relative humidity. 6. relative humidity: the amount of water vapor in a given sample of air compared with the maximum amount of water vapor that can exist in air of the same temperature. 7. saturated: filled with water. 8. water vapor: water in a gaseous state. 9. wet bulb depression: the temperature difference between the dry bulb temperature and the wet bulb temperature in a psychrometer.

Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. When you go outside on a hot summer day, usually your body begins to sweat. Why does your body do this: Evaporating sweat is carrying heat away from the body .

2. Humidity is the amount of moisture in the air. Do you think sweating cools you down more on a dry day or a humid day: Sweating can be more effective on dry days.

Gizmo Warm-up When sweat evaporates, heat energy is removed from our skin and our bodies cool down. But the amount of water vapor air can hold is limited, so sweat can only evaporate if the air still has the capacity to hold more water. If the humidity is high, less water can evaporate from the sweat on your skin. The amount of water vapor in the air compared to the maximum amount air can hold is known as relative humidity. In the Relative Humidity Gizmo, you will use a psychrometer to determine relative humidity. A psychrometer has two thermometers. The dry bulb thermometer measures air temperature. The second thermometer has

a wet bulb. As water evaporates from the wet bulb, its temperature decreases relative to the air temperature. 1. Do you think the wet bulb will cool down more on a dry or humid day: Maybe on a dry day.

) and observe the thermometers for about 24 simulated hours. Describe 2. Click Play ( some of the changes in temperature for both thermometers: The dry and wet bulb both rise in temperature from 3 am to 5 pm when the sun sets at 5pm the temperatures st\tart to go down 3. Activity A: Get the Gizmo ready: Measuring relative humidity

● Click New. ● Turn on Show relative humidity.

Question: How can you use a psychrometer to measure relative humidity? 1. Predict: How will relative humidity relate to the temperature of the wet bulb thermometer:the water will evaporate from the wet bulb making the thermometer cooler.

2. Gather data: Click Play, and click Pause ( ) at several random times. Record the dry bulb temperature, wet bulb temperature, and relative humidity. Trial

Dry bulb temp. (°C)

Wet bulb temp. (°C)

Relative humidity (%)

1

29.3

23.3

60%

2

27.7

22.2

62%

3

24.3

20.0

67%

4

24.7

20.3

67%

3. Analyze: What patterns do you notice: As it gets to night time the dry bulb and wet bulb temperatures start to go down but the humidity starts to increase.

4. Measure: Select the TABLE tab. This table will help you to determine relative humidity. A. Click Play and then Pause. What is the dry bulb temperature: 21.8 B. What is the wet bulb temperature:17.8 C. What is the difference between the dry bulb and wet bulb temperature: 4 This value is called the wet bulb depression.

D. Find the dry-bulb temperature on the table’s left column. Then find the wet bulb depression along the top row. (Use the dropdown menu to see different temperature differences.) The relative humidity is found at the intersection of this row and column. What is the relative humidity:68 Click on the CONTROLS tab to check your answer. (Your value should be close.)

5. Practice: Select the TABLE tab again. Click Play, and click Pause at several random times. Each time, record the dry bulb temperature, wet bulb temperature, wet bulb depression, and the relative humidity. Trial

Dry bulb temp. (°C)

Wet bulb temp. (°C)

Wet bulb depression (°C)

Relative humidity (%)

1

23.5

19.7

3.8

70

2

19.7

18.2

3

11.8

10.3

1.5

83

4

18.1

17.2

0.9

92

1.5

87

6. Interpret: Examine the psychrometer table on the TABLE tab. A. As the wet bulb depression increases, what happens to the relative humidity: The wet bulb depression increased and the relative humidity decreased

B. As the dry bulb temperature increases with a constant temperature difference, what happens to the relative humidity: The relative humidity started to decrease. C. How do you think the amount of water vapor air can hold changes as air temperature increases:The air can hold lots of water vapor so it increases.

7. Think about it: Warm air is able to hold much more water vapor than cold air before it becomes saturated (100% relative humidity). How would you expect the relative humidity of air to change as air warms up in the morning? How would you expect it to change as air cools in the evening? Test your ideas using observations from the Gizmo and describe your results below: As air warms, its capacity for holding water vapor increases as it starts to cool, the capacity decreases.

Activity B:

Get the Gizmo ready:

Measuring dew point

● Click New. ● Turn on the Show water bucket.

Introduction: Air is saturated when the relative humidity reaches 100%. If saturated air is cooled down, the amount of water vapor the air can hold will decrease, so water vapor in the air will begin to condense into drops of liquid water. The temperature at which condensation begins is called the dew point. Question: How can you measure the dew point? 1. Observe: Set the temperature (T) of the water bucket to 50.0 °C. A. Look at the sides of the bucket. Is there any condensation there: no B. Slowly decrease the temperature of the water bucket until you see condensation form. What temperature does condensation first form on the bucket:5.4 This temperature is the dew point. Turn on Show dew point to check your answer.

2. Measure: Click Play and watch the dry bulb temperature, relative humidity, and dew point for several days. Click Pause at random times and record your readings in the table below. Take readings at least once for a relative humidity above 70% and below 30%. Trial

Dry bulb temp. (°C)

Relative humidity (%)

Dew point (°C)

1

17.4

66

11.0

2

13.4

81

10.1

3

21.8

55

12.2

4

20.7

57

11.9

3. Analyze: Compare the dew point to the dry bulb temperature and the relative humidity. A. For which relative humidity was the dew point closest to the air temperature: 100%

B. Why do you think this is the case:If the dew point is significantly lower than the air temperature, the air is dry and can still hold much additional water vapor

4. Gather data: Now, gather data for a whole day. Fill in the table below. Time

Dry bulb temp. (°C)

Relative humidity (%)

Dew point (°C)

1:00 A.M.

16.3

28

-2.2

5:00 A.M.

17.9

31

0.6

9:00 A.M.

32.8

64

25.0

1:00 P.M.

32.6

36

15.5

5:00 P.M.

29.7

68

23.2

9:00 P.M.

24.9

81

21.4

5. Describe: Look at the data in your table. What patterns do you see:The numbers kept increasing and decreasing .

6. Interpret: Based on your data, describe what the weather probably was like that day: Maybe cloudy, windy, and humid and hot.

7. Apply: Think about real-life situations when condensation occurs. A. Why do water droplets form on the outside of a cold can of soda: It could be because of condensation

B. Why does dew form on grass in the early morning:water vapor in the air will begin to condense faster than water is evaporating

C. Describe another example of condensation, and explain why it occurs:eye glasses fogging up when you enter a warm building on a cold winter day...