Introduction
This topic lends itself to a number of curriculum ideas. Problem-solving skills; appreciation of technology and its impact on society; the history of science/technology; career paths; language development; and flow chart design could all be covered in a unit on air and flight.
Although the flight activities in this topic can be used for all levels of primary school, older students tend to get more out of these activities, as they are able to discuss the concepts at a deeper level. None of these activities can be explained without an understanding that flight is occurring through air. The idea of air is thus a prerequisite to understanding flight.
Key concepts of air and flight
The activities in this topic are designed to explore the following key concepts:
Early years
- Air is all around us.
- Wind is moving air.
- Air fills up spaces if allowed.
- Air can push or cause pressure on things.
- Air slows down falling objects such as paper, balls and parachutes.
- The shape and size of an object affects the nature of airflow around it, hence the air resistance.
- Planes and other flying things are held up by the force of air on their wings.
Middle years
- Air in the atmosphere exerts a pressure in all directions.
- The atmosphere can exert a surprisingly strong force on objects.
- ‘Sucking’ reduces pressure, causing a force imbalance towards the low-pressure region.
- The pressure of air is used in many applications (tyres, hoists, etc.).
- Air pressure differences tend to equalise.
- A moving stream of air has reduced pressure.
- Air has weight.
- Air expands on heating, causing a pressure increase if it is contained.
- Hot air is less dense (or more spread out) than cold air, and rises.
- Air consists of a mixture of gases, one of which (O2, dioxide) is necessary for burning.
- Objects can be shaped to either minimise or maximise the force of air on them.
- A flat object such as a plane wing, a boomerang or a paper tube can be supported by forces that arise due to differences in airflow across the top and bottom surfaces.
- To every action there is an equal and opposite reaction: a stream of air (or water) forced from a balloon or rocket will cause a force back on the balloon or rocket to propel it.
- The force from air on a moving object depends on the surface area, and the shape of the object.
- Wind is moving air.
Students’ alternative conceptions of air
Research into students’ ideas about this topic has identified the following non-scientific conceptions:
- Younger children often only associate air with wind, which is moving air. Presumably this stems from a view that only directly observable entities are real. Thus, they are most likely to interpret ‘air is everywhere’ as meaning that air is only outside.
- Young children will think that air moves unaccountably into or out of enclosed spaces, to explain why there might or might not be air in upturned glasses, containers or cupboards.
- The wind is caused by trees swaying.
- Fans and moving objects create air (rather than simply set air in motion).
- Students can attribute the causes of these ‘air taking up space’ or ‘air pressure’ activities to their own action (‘the water comes out because we lifted our finger’, or ‘the tissue remains dry because we were careful’) or use explanations based on analogy rather than identify causal mechanism (‘the air was trapped’). Thus students can have an ‘alternative’ view of the nature of scientific explanation.
- Suction involves creating a vacuum, which causes a negative, pulling force on objects. In fact ‘suction’ is often not thought of so specifically but rather is a term used to describe a class of phenomena. In this sense the use of the terms ‘suction effect’, ‘suction cap’ or even ‘suction force’ can be quite helpful in locating causes for movement or identifying the nature of a phenomenon. It is the identification of the term with air ‘pulling’ that is incorrect.
- Pressure only operates in a downward direction.
- Air exerts a force only when it moves.
- Air has no weight or negative weight.
- Hot air has negative weight, which causes it to rise.