We probably should begin by talking about temperature. Temperature, which involves molecular activity, can be measured with a thermometer. To introduce this idea, a good lesson is found in “Introduction to Earth Science” by Norman Abraham, Donald Chaney , Michael Moores, Robert Swift, Jerome Notkin and published by Rand McNally Company 1972.
To start the student thinking, place a one hole stopper containing a 30 cm glass tube with a plug of colored water that will move up or down into a flask containing only air. Covering and uncovering the flask with your hand will cause the plug to rise or fall. Have the students explain why this happens. You might also want to try using a two hole stopper and inserting a thermometer into one of the holes to see if a change in temperature can be observed. Trial and error? (see fig. 1) We are aware that temperatures at or near the equator are higher than those at or near the poles. What could cause some of these differences?
An activity that appears in several textbooks is to take a flashlight and shine it on graph paper both head on an at an angle from the same height. Have the students notice the light intensity and also the area covered. After doing this do the same thing but this time use a thermometer angled and perpendicular to the light source and record the temperature over a period of time. These activities should help the student realize that a locations latitude has an effect on the daily temperature. You might also bring in the fact that the sun”s rays also travel through more atmosphere away from the equator thus filtering, absorbing, and reflecting more energy than near the equator.
Temperature is also affected by altitude. As we ascend into the atmosphere the temperature decreases. Show the class pictures of areas that are nice and green and warm but in the background there are mountains covered with snow. Ask them how this could happen. Mountain building, by subduction, is one of the results of Plate Tectonics. Mountains have a bearing on the precipitation and temperature of an area by causing the air to condense and cool as it rises over the mountain.
Ocean currents can also affect the temperature of an area by bringing warm or cool currents to an area which cause conditions to be more stable by preventing wide temperature ranges as water warms more slowly than land and also cools off less rapidly than land.
A heat exchange experiment is helpful at this time. Fill a styrofoam cup with hot water and another with cold water. Cover and connect each cup with a metal rod. Place a thermometer in each cup and observe the temperature changes in each cup and the final temperature in each cup. Oceans also effect the temperature of an area by cloud formation. As evaporation takes place at the surface it rises, cools and forms clouds. These clouds block out radiation from the sun which in turn causes the oceans to cool off. After cloud formation is reduced, the oceans will again begin to absorb radiant energy from the sun and the warming trend will begin again.
A way of observing the effects of blocking solar radiation is to check the effects of the oil fields burning in Kuwait. You will see that the temperature has decreased due to the smoke blocking out the radiation from the sun.
Other activities that can be performed are the heating and cooling of sand and water, the heating and cooling of water in a shiny aluminum container and a black container to help the student realize how water, land and ice can effect temperature and heat.
Air Pressure
Air pressure is affected by temperature, water vapor and elevation. We measure air pressure with an instrument called a barometer. This instruments indicates the condition of the atmosphere. As the air rises the pressure lessens causing the barometer to have a lower reading. If this air is saturated at ground level it will condense to a liquid at higher cooler elevations. The opposite happens for high pressure. Dry cool air descends causing the barometer to register a higher reading.
Relative Humidity
Relative humidity can be measured with a wet and dry bulb thermometer called a psychrometer. This gives an indication as to how much water vapor is in the air compared to how much it can hold at that temperature and pressure.
