Am I hot or am I cold?

By Susan M. Frack and Scott Prickett

BACKGROUND:

Air is sometimes hot. Sometimes it is cold. We measure the temperature of the air with a thermometer. The air that surrounds the earth is warmed by the sun. That's why the air is usually warmer during the day when the sun is shining-- than at night.

In the summertime, the sun's rays shine more directly on the earth than during the winter. Also, on summer days the sun shines for more hours than it does on winter days. This makes summer temperatures higher than winter temperatures.

MATERIALS:

thermometers mounted on metal or plastic backs --for student use
large thermometer for demonstration use
hand-held blow dryer
small electric fan
ice cubes in plastic bowl
flashlight--lantern-style is best
soccer ball
stop watches
drawing paper
markers

OBJECTIVES:

Tell how the air around the earth gets heated and cooled by the sun.
Practice using a thermometer to keep track of the daily temperature for 2 weeks.

MOTIVATIONAL SET:

Turn on the blow dryer and let children feel the air. (CAUTION-- the blow dryer can be very hot. Don't allow children to get too close to it.) Then turn on the fan and let it blow across the bowl of ice. Allow the children to feel this flow of air. Ask them to talk about the difference in how the air felt in each situation. Ask why they felt warm and cool air. Explain that today they are going to figure out how nature makes the air around the earth how and cold and how people measure the amount of heat or coldness in the air.

TEACHING STRATEGY:

1. Ask students to tell where they believe the heat in the air/atmosphere comes from. Accept any/all ideas. Repeat question for the coldness in the air.

2. Using the ball to represent the earth and the flashlight to be the sun, discuss with the children how the sun warms up the earth and how it then cools off at night. Also show how the earth tilts toward the sun in summer and receives more sun and how it tilts away from the sun in the winter and receives less sun. Students may want to take turns holding the ball and light as they re-affirm their knowledge. (the book Sunshine Makes the Seasons by Franklyn M. Branley is an excellent resource)

3. Using the larger, teaching thermometer, show it to the class and explain its name and its functions. ( Younger students will not need as much detail about the number of degrees, etc. Use your own judgment as to how much detail you include in your explanation.) EXPLANATION: Look at the thermometer. Do you see the red liquid in the round part at the bottom of the glass tube? As the air becomes warmer, the liquId grows bigger, or expands. It needs more room. Where can it go?? (only up the tube) When the air becomes es cooler, the liquid cools off and contracts. It takes up less room. What happens?? (it slides back down the tube,) Lines on the thermometer show the temperature in degrees. Marked on one side of the Fahrenheit or F scale. Marked on the other side i s the Celsius or C scale. The F scale has 180 divisions between the freezing point of water (32 degrees) and the boiling point of water (212 degrees). The C scale has 100 divisions between the freezing point of water (0 degrees) and the boiling point of water (100 degrees). The Celsius scale is the one most used by meteorologist.

4. Have students all stand up and pretend to be liquid in the thermometer. Turn on the flashlight and shine it back and forth across the group as you tell them it is the sun. Ask them what will happen to them as the sun shines on them. They should say they will warm up and take up more space. Have them move slowly apart and take up more space in the room. They are "expanding". Turn off the flashlight because it is now nighttime. Ask them what will now happen to them. They should say "cool off" and "come back together". Have them move slowly back together as they take up less space and "contract". Do this several time to simulate several 24 hour time periods.

5. Pass out student thermometers and have students complete measuring activity in Appendix A. (See hyper studio program to show children the correct way to read a thermometer) *For younger students, this may be done as a whole class activity with the teacher helping to read the thermometers and students recording on a large poster size data chart. Older students should work in groups of 2 or 3. They should take turns timing, placing the thermometers, and recording data. The teacher will need to specify that Celsius, C, should be taken.

CLOSURE:

Bring the students together to go over the 3 questions at the end of the activity.

ANSWERS:

1. & 2. will vary according to the time of day.
3. Don't put the thermometer in the sun because you are measuring the air's temperature and not the temperature of the sun's rays.
Review the concepts of how the air is warmed by the sun and cooled by the lack of sun and of how the thermometer works.

EVALUATION:

Students will match temperatures to pictures of items. Students will read thermometers and write down the temperatures. Students will draw arrows to show which way the liquid will move in the thermometer under the shown conditions. Students will fill in the blanks about the sun's rays. (Appendix B)

Students will keep track of the daily inside and outside temperature for 2 weeks. They will discuss differences between the two each day as well as differences between the days at the end of the 2 weeks.

ADDITIONAL ACTIVITIES:

Literature The Riddle of Aunt Red Wing by Nancy Wood.
Penguin Bulletin board

RESOURCES:

Arnold, Caroline; Ladybird First Facts About Weather, Ladybird Books, England, 1990.
Branley, Franklyn; Sunshine Makes the Seasons, Harper and Row Publishers, New York, NY, 1985.

APPENDIX A:

HEAT IS NEAT

GET READY TO PUT YOUR THERMOMETER TO WORK!

RULES:

Always stand the thermometer up. It is easier to read.
Read the thermometer without picking it up.
Have your eyes level with the thermometer when you read it.
Try not to touch the bulb of the thermometer with your hands. Your hands are warm and will raise the temperature of the thermometer.

DIRECTIONS:

Take the temperature in each location on the list. Leave the thermometer "stand" in each location for the amount of time listed. Use the stop watch to time yourselves.

Write the temperature of each location below the correct thermometer and color in the correct number of degrees on each thermometer.

Inside air--Place the thermometer on the chalkboard tray for 5 minutes.
Outside air--Place the thermometer against the shady side of the building for 5 minutes.
Hot air--Hold the thermometer in front of your mouth and breath on the bulb of the thermometer slowly for 2 minutes.
Icy air--Stand the thermometer in the bowl of ice cubes for 5 minutes.