Task 2

Materials and tools for a working group:

two balloons, string, PET bottle (or glass bottle), sand, wooden skewers, cork stopper (or clothes pin)

In the second task, pupils will find out whether the weight of the balloons will be the same/ different depending on the temperature of the air the balloons are inflated with. The teacher presents the pupils worksheets in which the picture is of equal weight and equally inflated balloons. The task of the pupils will be to make predictions about whether the weight of the balloons will change as the temperature changes. After writing the predictions down, the teacher discusses with the pupils and leads them to justify their predictions (underpinning knowledge/own experience, e.g. I think warm air is „lighter“ because even in a large balloon that flies, a burner is used to warm it up).

After the discussion he will ask them to propose a way of verifying their predictions, resp. way they could heat and cool the air in the balloons. One balloon can be placed e.g. on a windowsill or under a table lamp (not too close to the balloon), or on a radiator and the other for a few minutes placed into the fridge. However, before carrying out the verification, pupils need to examine the weight of the balloons before influencing them. Both balloons would have the same weight, i. the isosceles weight should be in balance. This is done by adjusting the balance so that it is in balance (with the balloons hanging) before influencing the temperature in the balloons. As the warm air rises upwards (its density is less than the density of the cold air around it), the hot air balloon will be “lighter” than the cold air balloon.