Asia-Pacific Forum on Science Learning and Teaching, Volume 3, Issue2, Article 3(Dec., 2002)
Russell TYTLER
Using toys and surprise events to teach about air and flight in the primary school
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Air and Air Pressure

The pressure from the atmosphere gives rise to many surprising phenomena. Some of these, such as drinking through a straw, we experience so often we tend to take them for granted, or explain them in other ways.

Young children find the assertion that 'air is everywhere' difficult to accept. Studies have shown that they tend to associate the presence of air mainly with open spaces, breezes and breathing, and will think, for instance, that a jar will contain no air. Some of the activities in this section are meant to reinforce the idea of air as a tangible presence, that takes up space and resists compression.

The idea that air takes up space, and competes for space with water, can be used to effectively explain most of these 'tricks'. The more powerful concept of air pressure is more difficult, but accessible in restricted form, for younger students. They tend to talk of the 'strength' of air, or of air 'pushing'.

Students tend to call up a range of conceptions to account for their observations of these activities, many of them quite useful over a range of phenomena. The idea of 'suction', for instance, while not acceptable as a scientific explanation, is more accessible to students (and adults) than the more powerful idea of competing pressures which underlies many of these tricks.

The idea of air and atmosphere is a very important to establish, since it underpins many science ideas. We have found that understandings of evaporation and the water cycle, for instance, are very dependent on the idea of a tangible atmosphere for water to evaporate into. Ideas about plant respiration, or of gas production in chemical reactions (such as between bicarbonate of soda and vinegar), depend on the idea of a gas for which air is the primary model.

Air is everywhere, and takes up space

By the age of 8 or so, most students will have a confident idea about air taking up space, and will be able to talk reasonably about some of these activities in terms of air movement, or air being squashed. However, the first few activities are quite challenging for lower primary school students.

It is instructive to talk with Grade 1 or 2 students about where air might be found; in a cupboard; a jar, or underneath the table. They can be challenged to collect air in plastic bags from places of their choice, trapping it by tying the top. Some comments:

I had no idea there would be air across the hall even though this door was shut tight.
I even found air in the toilet bowl with the door shut!

Older students might explore whether there is air in soil, or in cork, by putting them underwater and watching for bubbles. They can also measure their lung capacity by taking a deep breath, and bubbling all the air from their lungs through a plastic hose into an upturned 4 litre container held full of water in a sink full of water. The amount of air can then be measured by seeing how much water is left in the container.

Watch video 1: ordinary (944 kB) or high (9.53 MB) resolution (in Real Player format)

Dunking a tissue
Container of water at least 15 cm deep. Glass, and box of tissues.

Push some dry tissue paper into the bottom of a glass, so that it won't fall out when the glass is upside-down.

Predict what will happen to the tissue if you push the glass, upside-down, underneath the water in the tub.Do you think the paper will get very wet?

Take the glass out and feel the paper (Observe)

Can you explain what you find? Revisit your predictions. Were your assumptions at fault?

Watch video 2: ordinary (627 kB) or high (6.2 MB) resolution (in Real Player format)

Commentary
DRY TISSUE

This dunking activity is counter intuitive for students, and relies on contradicting a visual expectation that things underwater get wet. The dry tissue activity is perplexing for younger students, who might say:

* The water would get in but air gets in instead through the lip (we tried this with a beaker, which triggered this explanation that the class found quite convincing)
* It will get wet if you leave it long enough.

It is worthwhile to let students play with these activities if possible, since they will explore all sorts of possibilities. Inevitably they will get the tissue wet by putting in the beaker at an angle! That resolves the problem for some, but they can be challenged to find out how many tissues they can keep dry inside the glass.... does water come part way up into the glass? The answer is no; the air takes up its space and won't be easily compressed.

Drawing what is happening in profile gives insight into where students think the air - water surface is. The two samples of children's drawings show their different understandings.

Some students link this activity with diving bells. By age 9 or so we have found most students can deal with explanations to these activities quite competently.

Watch video 3: ordinary (937 kB) or high (6.2 MB) resolution (in Real Player format)

Copyright (C) 2002 HKIEd APFSLT. Volume 3, Issue 2, Article 3 (Dec., 2002). All Rights Reserved.