Air Air
Air
Air
Introduction
We may not realize it, but the air that surrounds us is exerting a huge amount of pressure on every square centimetre of our bodies. In these activities students explore the impressive force of air and learn how air pressure affects their daily lives.
At this very moment, we have the equivalent weight of a car pushing down on our heads. Do you see anything? Although we can't always feel it with our senses, air is all around us, exerting large amounts of pressure on our bodies. In these activities, students apply the concepts of air pressure to demonstrate how air affects our daily lives.
Objectives
- Describe the characteristics of air.
- Explain how air pressure works.
- Discuss how air pressure affects our daily lives.
Background
We are constantly surrounded by lots of tiny and invisible air particles. We often think of air as being something light and weightless. In reality, air is a gas that takes up space and has mass (weight). Since there is a lot of "empty" space between air molecules, air can be compressed to fit in a smaller volume.
Air not only has mass, but exerts pressure as well. The particles of air push in all directions and the force that is exerted is called air pressure.
While air pressure can refer to the pressure of air within a confined area (car tire or football), atmospheric pressure specifically refers to the air pressure exerted by the air molecules above a given point in the Earth's atmosphere. The closer we get to the Earth, the higher the atmospheric pressure due to the weight of air particles above. This is why there is less air pressure at the top of a mountain than at sea level. The weight of air above compresses the air particles near the surface of the Earth, creating a higher density of particles. The tool used to measure atmospheric pressure is called a barometer. You cannot use a barometer to measure the air pressure inside a tire, a football, or an air mattress.
When we jump into a pool, we feel the weight of the water pressing down on us from all directions. This force is known as water pressure. The deeper you sink, the more pressure you will feel. This is because you have the weight of the water on top of you trying to compress you. To help us visualize air pressure, imagine that we're living at the bottom of an ocean of air. At sea level, the air pressure is greater than on the top of a mountain since you have the weight of more air pushing down on you.
How heavy is that air? A cube of air 1 metre per side has a mass of 1 kilogram. The Earth's atmosphere is about 480 kilometres thick. This means that on the surface of the Earth, we have 480 kilometres of air pushing down on us. That's 1,700 kilograms on each of our heads (which is roughly the equivalent of the weight of a male hippopotamus!). So why don't we get flattened by all that air pressure? We have air and fluids inside your body that exert a pressure outward, cancelling out the atmospheric pressure around us. This ensures that our bodies do not collapse under the weight of the air around us.
One of the most important concepts to remember in this unit is that air always flows from a place with high pressure to a place with low pressure. Air will perform amazing feats to get from a high-pressure region to a low-pressure region, including pushing and lifting things in its way. Air flowing from a high-pressure region to a low-pressure region is often felt as wind. To help students remember the direction of airflow, they can use the phrase "winds blow from high to low."
In the following activities, students will discover how changes in air pressure contribute to many different things, including weather patterns, our respiratory system, and the lift required by airplanes.
Entire Lesson
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Other Resources
Science World Resources | Activity | Egg in a Bottle
Science World Resources | Make & Take | Air Cannon
Science World Resources | Full Lesson | Balloons | Flight
Science World at TELUS World of Science | Mitchell Odyssey Foundation Gallery: Eureka!
Comments
•Kids Under Pressure: the game as written has no 'goal', so kids don't see the point. Game can be modified into freeze tag, but where the playing area gets progressively smaller. Anyone who goes outside of boundaries becomes auto-frozen.
•Balloon in a Bottle: kids have small lungs! Activity may be better suited as a competition b/w 2 facilitators.
•Have You Got Enough Puff?: for best visibility, have volunteer lie face-up on floor. The extension activity using a balloon attached to the funnel doesn't seem to work.
•Plane-wing Simulation: hold paper strip w/ both hands, & blow lightly but steadily. Blowing quickly or strongly will make paper flap (but this could be a good followup to activity).
•Human Lung Simulator: it worked really well to make the balloon lung in stages.
•Air Cannon: duct tape works best for ensuring an airtight seal; pre-cut enough strips before session. Air cannon seems to work better if you reverse the design found in the program doc: instead of placing balloon on the bottom/cut-out part of cup, you place it on the top/mouth of cup, then cut out the cup bottom to make the front opening of the air cannon. This also eliminates need for paper & elastic bands!
•Build a Barometer: probably better suited as a regular-school activity, rather than a SSC M&T.
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