5 THE COMPOSITION OF THE EARTH AND ITS ATMOSPHERE AND THE PROCESSES OCCURRING WITHIN THEM SHAPE THE EARTH’S SURFACE AND ITS CLIMATE

Task 3

WORKSHEET

Materials and tools for a working group:

2 jars, 2 balloons, 2 rubber bands, scissors, 2 larger containers, cold water, hot water

In this task, pupils will again explore the air-temperature characteristics.

Pic 57: Jar with balloon as a lid

At the beginning of the task, the teacher provides the pupils two jars (3dcl is sufficient). It is suitable to have glasses in the classroom at least 15 minutes before the activity starts (due to obtain room air temperature). Then he takes one cup and attaches the balloon on the jar mouth with a rubber band (for better handling, the pupils can cut the balloon) and asks the pupils if they think that the air temperature can affect such a balloon and how it can manifest on it. The teacher discusses with the pupils. Pupils draw their predictions about what happens to the balloon when the temperature changes, after the worksheet. After discussion, it will invite pupils to suggest a way to verify their predictions.

The teacher (if possible) should lead the pupils to realize all the proposed procedures. If the pupils do not propose anything, the teacher guides the pupils by asking questions about their proposal: pour the same amount of water into two identical containers, one hot and the other cold (about 4 cm from the bottom of the glass). Since we lead students to objectively determine the reality, the volume of water in both containers should be the same. Then we put cups with a balloon on top at the same time into both containers. In this way, pupils verify their predictions through observation.

Then the teacher can ask if they think this reaction is reversible, ie if we put the cup with the convex balloon in cold water, or if we put it in the refrigerator, whether the balloon will return to its original position or spill inside the glass.

Recognizing that air temperature affects its properties (in this case, air density) is an important step for further investigation of the weather – e.g. air pressure. The teacher does not have to explain the concept of air density to pupils. An important finding for pupils is that air changes its properties when temperature changes; when heated it rises upwards and when cooled down. With the air temperature, the movement of the particles in it changes as well – as the temperature increases, the movement of the molecules increases = the increase in the volume of substances during heating and the decrease in cooling.