HamiltonJHSB4

Title: Measuring Humidity

Grade Level: 8

    This is a picture of humidity at its most extreme. This is a fogbank rolling down a California hill. Fog is simply water vapor at 100% humidity. Air that is at 100% humidity does not always form fog. When it is raining, the humidity is at 100%, too.
    Why are we concerned about humidity? In hot weather, the higher the humidity, the more uncomfortable we are because the humidity makes the heat feel even hotter! This is referred to as the heat index. At night, humidity holds the heat making the nights warmer than they would be on less humid nights. On cloudless and low humidity nights, the temperatures can drop many degrees below what was measured on a cloudy, humid night.
    As you can see, humidity goes a long way in determining how comfortable the weather conditions are for you and me.

Subject: Science

Learner Outcomes:

The student will assemble a device for determining the relative humidity.
The student will use the psychrometer that has been made for making a series of weather observations.

Duration of Lesson:

It will take one day to create the psychrometer.
It will take small parts of class sessions over a three week period for making observations. (see teacher notes)

Materials:

Cardboard (heavy) about 6" x 9"

2 alcohol thermometers (identical)

Beaker of water

Piece of gauze

tape

string

Humidity Table

Data table

Technology Tools / Courseware:

Computer with Internet connection.
TV with cable connection.

Teacher Notes:

Safety: Students are working with glass thermometers. Students need to be aware of the possibility of being injured. Obviously students should behave in a mature manner. The use of mercury thermometers should be strongly discouraged.
Introductory and follow-up extension activities involve use of the Internet. There are many sites available on the Internet involving weather and weather information. At the eighth grade level, it should not be necessary for the teacher to "pre surf" Internet sites for the students, but this is up to the teacher.
You could substitute a glass jar for the beaker, depending on what is available for you to use.
Part of the lesson involves student groups making daily outside observations of current weather conditions. This needs to only take five minutes. You can have your students record their observations and go on with the day's lesson. After three weeks (or a period set by you), you may bring the lesson to its closing phase.
Optionally, if you have a TV in your classroom connected to cable, have your students compare their weather readings to the Weather Channel.
If you don't have access to a TV, the following links on the Internet have similar information about your local weather conditions:

Procedures:

1. Have the students check the Internet for information about air pressure to better understand the concept. Here are some good sites:

Encarta Online Encyclopedia - defines humidity
Heat and humidity can be deadly combination - an article on the effect of humidity on heat
How a Hair Hygrometer Measures Humidity - defines humidity and describes how to measure it

Discuss with your students what is humidity and how it affects the weather. Make sure that they know that relative humidity measures how much of the water vapor that the air can contains and compares it to how much the air can contain at a given temperature. See if they can make the connection that relative humidity will go down as the temperature rises and will increase as the temperature falls.

2. Before during the lab, discuss with your students the following concerns:

Safety concerns
How to work in cooperative learning groups Unfamiliar with Cooperative Learning groups? Click here for a description and links.
Jobs of each member of each group (i.e. leader, materials gatherer, quality control, information recorder)
Inform the students that they will be using their psychrometer to take observations of the weather for the next (insert period of time) so they should a) make it sturdy; b) treat it carefully; and c) store it carefully

3. Directions for the lab: (refer to the drawing below)
        1. Send the materials gatherer to obtain the materials.
        2. Carefully tape two identical alcohol type thermometers to a sheet of cardboard so the number scale and the red alcohol is visible. The ends of the thermometers should hang down below the edge of the cardboard (see below)
        3. Using some string, carefully tie the small (2 cm by 2 cm) piece of gauze to one of the thermometers. Be sure the gauze won't come off and that it is in contact with the bulb of the thermometer.

4. Directions for using the psychrometer.
        1. Carefully dip the thermometer with the gauze tied to it into your beaker of water until it is thoroughly wet.
        2. You can either wave the cardboard or use a sheet of paper as a fan and wave it over the psychrometer. The important thing is to have air moving over the two thermometers.
        3. When the alcohol in the two thermometers stops moving, record the temperatures on your data table. Click here to get a copy in Word 97/2000 format that can be printed.
        4. Using the Humidity Conversion table, determine the relative humidity and record it on your data table.
        5. Over the next three weeks (or a period of time determined by the teacher) students should use their home-made weather instruments outside to take weather readings and record them on their data tables. This can take the first five minutes of class time each day.
        6. Students can compare their weather readings with those of the Weather Channel on TV or sites on the Internet that display local current weather conditions. (See teacher notes, above).

5. Conclusions. Discuss with your students what effect did they observe that humidity had on the weather. Perhaps it was raining on one of the days your students made observations. If so, did they measure a relative humidity of 100%?

Modifications:

1. This activity calls for the use of cooperative learning groups. Students with special needs can satisfactorily complete these activities when working in groups.
2. This activity is commensurate with IEP requirements.

Enrichment Activities:

1. There is a wealth of information on the Internet that the student can access using computers. Here are a few suggestions:

Make Your Own Hygrometer - instructions on how to make another kind of measuring device (includes a table for Fahrenheit)
Make a Psychrometer - instructions on how to make another kind of psychrometer

2. You may wish to have your students use a good search engine to look for more information. Afterwards, students could submit written reports describing the information they have discovered. Here is a suggested format:
        a) When you find a good site and have read it, shrink the browser to your toolbar (if using Windows 95/98) by clicking on the underline box in the upper right corner of your screen.
        b) Start your word processor and then shrink it to your toolbar also.
        c) Click on the browser button on your toolbar to restore it. Click on the address to highlight it and right click to get a menu. Select "copy" by clicking on it. Shrink the browser to the toolbar again.
        d) Click on the word processor button on your toolbar to restore it. Type your name, date and class on separate lines. Highlight the three lines and click the right alignment button. Press <enter> twice to skip two lines.
        e) Type the word "Address" and then click the paste button. The address of your web site will appear. If it is still right aligned, simply click the left alignment button on your toolbar. Press <enter> twice to skip two lines.
        f) Type in a brief description of what you learned on the web site. Several paragraphs should do.
        g) Save your work in the method your teacher wants and submit it to your teacher in the method your teacher wants.

Evaluation / Assessment

1. The students will be observed and evaluated by the teacher using the Rubric Assessment. (Formative and Summative)

2. The students will turn in a completed Data Table. (Summative)

West Virginia Goals and Objectives:

Eighth grade Science: 8.8 8.10 8.13 8.17 8.22 8.72 8.78 8.89 8.98

National Standards

References:

1 The following links to the World Wide Web:

Encarta Online Encyclopedia
Heat and humidity can be deadly combination
How a Hair Hygrometer Measures Humidity
Intellicast.com
Make a Psychrometer
Make Your Own Hygrometer
UM Weather
Weather Channel.com
Weather Underground

2. The following documents written by the author:
Cooperative Learning Groups

3. The midi file was Sweat (A La La La La Long) - artist unknown.

Author:

Robert Wharton
Hamilton Junior High School
http://hjhs.wood.k12.wv.us
Parkersburg, WV
email: rwharton@access.k12.wv.us

Links to other Lessons in this Unit


Unit Overview	Weather Vanes (Science)	Barometer (Science)	Psychrometer (Science)


Average Weather?? (Mathematics)	But What Should I Wear???? (Mathematics)	Birthday Weather and News (Language Arts)

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