The air around us
Explore the science concepts that underpin the nature and properties of air.
The concepts listed just above the overarching concepts reflect learning at New Zealand Curriculum level 1 and show how they may build in sequence to level 4. The overarching science concepts are fully developed concepts and might not be achieved until level 7 or 8.
Some of the text is courtesy of the New Zealand Ministry of Education’s Building Science Concepts Book 30 The Air around Us: Exploring the substance we live in. The links to Hub resources provide additional background information and classroom activities that will support teachers to scaffold the development of their students’ conceptual understanding about the nature and properties of air. The images provide a means to initiate discussions, check student thinking and consolidate student understanding.
To use this interactive, move your mouse or finger over any of the green labelled boxes and select to obtain more information.
Download a PDF file of the transcript here.
The article Building Science Concepts: The air around us provides additional science and pedagogical information.
Interactive background image courtesy of Professor Peyman Zawar-Reza.
Transcript
Objects that are more dense than air will ‘sink’ through it
Most objects on Earth that are visible have particles more tightly packed than air and predictably will sink (totohu) through it.
Some objects (like gliders and kites) appear to float rather than sink due to the forces that keep them aloft.
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Maize (sweet corn) flowers (falling pollen)
Image acknowledgement: undy licensed from 123RF Ltd
Objects that are less dense than air will ‘float’ in it
For something to float in air, it needs to be lighter than the same volume of surrounding air. Its particles are either lighter or less tightly packed than the particles of the air it is in.
The hot air inside a hot air balloon is less dense, where the air particles are not as closely packed together. This warm air inside the balloon is lighter than the air outside the balloon so the balloon will rise.
Helium balloons float because helium is less dense than air. Helium atoms are very, very small and can escape through the balloon material, which causes the balloon to eventually sink.
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Image acknowledgement: Child with stones, morrbyte; hot air balloon, mattkaz; both licensed from 123RF Ltd
Some things can float in air
Objects that float in air are sometimes only momentarily supported by the air. These objects can include bubbles, thistledown, balloons, dust, smoke and pollen.
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Image acknowledgement: anglianart, 123RF Ltd
Air is all around us, even though we can’t see it
We live in a mixture of gases that we call air (hau takiwā). Our atmosphere (kōhauhau) is the layer of air that surrounds Earth. Almost all (99%) of this mixture consists of two gases: nitrogen (78%) and oxygen (21%). The remaining 1% includes argon (0.9%), carbon dioxide (0.03%) and variable amounts of water vapour, traces of hydrogen, ozone, carbon monoxide, helium, neon, krypton and xenon. Although the air becomes less dense as you go up in the atmosphere, the proportions of gases in the mixture remain the same, regardless of how dense the air is.
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Image acknowledgement: Public domain
We experience moving air as wind
Although we may not see air, we can feel it when we make rapid movements through it, when the wind blows or when we experience airflows such as a draught. Our body experiences the air pushing harder against the skin on one side of our body than the other. This may require us to exert energy to remain upright or to maintain the speed at which we are travelling.
The energy from the push of the wind can be used to generate electricity. This is called wind power.
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Image acknowledgement: Cath Samson, Anna Spence
Spaces that look empty usually have air in them
Empty space at the Earth’s surface might look empty, but it is almost always filled with air. An empty drink bottle can be empty of liquid but full of air. If a plastic bottle is squeezed, the air can be felt against our skin.
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Image acknowledgement: pspatarapol, 123RF Ltd
Air particles spread out to fill all the space available to them
Air behaves in the same way as any other fluid (wē). It flows and spreads into spaces that are not otherwise occupied. Unlike a fluid, however, it can be squashed (compressed). When a bike tyre is pumped up, more and more air is pushed in to that space, and the air is spread evenly throughout the space but under increasing pressure.
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Image acknowledgement: Evan Goldin
If we remove all the air from a space, we can feel the air outside ‘pushing’ to get in
If the air is sucked out of a plastic drink bottle, the walls of the bottle buckle inwards. This occurs because the pressure of air on the outside is greater than that on the inside. If all the air is removed from a container, it is said to contain a vacuum (korekore).
An everyday example of this is vacuum packaging. Air that could cause a food to spoil or go stale is removed from the package, and the push (pana) of the air outside causes the packaging to press inwards against the food.
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Image acknowledgement: ryzhov, 123RF Ltd
Air particles moving around create a ‘push’ against the surfaces they collide with
An inflated tyre is firm because of the ‘push’ of the air particles against the inner tyre wall.
When we drink from a plastic bottle and prevent the air moving in to fill the space of the lost liquid, the air outside the bottle has more ‘push’ than what is inside the bottle. As a result, the bottle collapses.
Wind is what we feel when the air particles move and flow around us.
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Image acknowledgement: The University of Waikato Te Whare Wānanga o Waikato
Air held in a space can create an invisible ‘push’
In an air-filled or pneumatic tyre, the air is held in by a valve (katirere). Air under pressure (compressed air) can support a lot of weight. At the same time, it can absorb impact by compressing further when, for example, a tyre hits a bump in the road.
Bubbles are another example of the push of air. When we blow a bubble, we push air into a film of bubble mixture or a layer of bubble gum.
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Image acknowledgement: The University of Waikato Te Whare Wānanga o Waikato
