Task 1: The weight of the air

For every working group, the teacher prepares one mirror or a piece of glass. Petri dish or a watch glass is also possible to use. Pupils breathe on the glass and watch what happens. They write their estimate in the prepared worksheet.

For the next part of the first task, the teacher prepares one balloon for each pupil and at least three bicycle pumps per class. Next, the teacher prepares a digital scale that has 0.1 g of accuracy and places a big cardboard box on it, with the scale display easy to be seen.

If it is not possible to see the display, the teacher makes a hole into the cardboard box so that it is possible to see through and read the values on the scale display. The teacher places the cardboard box on the scale, pupils put uninflated balloons inside and after that the teacher resets the scale (TARE button).

Pupils inflate the balloons with the bicycle pump, tie them up tightly and put them carefully back into the box. When all the balloons are in the box, the teacher or a chosen pupil reads the value from the display and write it on the board or clearly tells the classmates. Pupils write their estimate and the read values in the worksheet and answer the additional questions.

Pupils put the cut off piece of marshmallow into the syringe and close it with the plunger. They leave the plunger in the upper position. The syringe, which contains the marshmallow, is entirely filled with air. Pupils use their thumbs to close the end tip of the syringe and start pushing the plunger down. They watch what is happening to the marshmallow inside the syringe. When the density of the air increases (its volume in the closed container decreases), the pressure inside the syringe starts to increase.

Then pupils release the plunger and push it down until it just reaches the marshmallow but not any further to avoid its deformation. The syringe contains the piece of marshmallow and little amount of air. Pupils close the end of a syringe tip by their thumbs again and start pulling the plunger of the syringe up. They watch what is happening to the marshmallow inside the syringe. When the volume of the air in the closed container increases (its density decreases) then the pressure inside the syringe starts decreasing. Pupils write their presumptions and observation in the worksheet.