Task 9

Materials and tools for a working group:

2 PET bottles (recommended thicker ones or alluminium bottles), colored paper, scissors, pencils, dropper, hot water (can also be from an electric kettle – approx. 50 °C), cold water

Procedure:

The task of the pupils will be to examine how temperature affects the rate of evaporation. At the beginning of the activity, the teacher can discuss with the pupils what they would do if they put the shirt on with water to dry them as quickly as possible. The discussion should suggest suggestions in which pupils should be able to illustrate the different ways of increasing the heat so that the water evaporates more quickly and the shirt can dry more quickly. They draw/write their proposals in the worksheet (first task worksheet).

The pupils write the predictions and the teacher discusses them with pupils. They cut out 2 squares about 2×2cm from colored paper (they should choose colors other than black and white paper for better visibility). They then fill 2 equally sized PET bottles with water – one cold water and the other warm water. It would be preferable to use aluminum bottles. The bottles will lie down and ensure that they do not move (eg they are supported by pencils on both sides). On the prepared squares of colored paper, 1 drop of room temperature water is dropped using a dropper and placed on the prepared bottles at once.

A variation in the activity may be the use of water in bottles of the same temperature, with hot water dripping on one square and cold water on the other. Thanks to the use of colored paper, it will be easy to identify which paper (on a cold/warm surface) will dry earlier.

Another option is that pupils can explore other types of material (fabric, paper, cotton swab, etc.) in addition to paper. Each group can prepare a different kind of material. They are then placed on the bottles at once and compare which bottles have dried (if at all) the material under investigation before. In addition, they can compare which material has dried earlier. In this way, pupils examine the evaporation of water. The teacher tends to discuss whether this phenomenon is also encountered in nature (rain puddles, reservoirs, etc.).