Describe properties of air and the interactions of air with objects in flight.
1. Provide evidence that air takes up space and exerts pressure, and identify examples of these properties in everyday applications.
1. Provide evidence that air takes up space and exerts pressure, and identify examples of these properties in everyday applications.
- When you blow air into a balloon it will increase in size. If you let air out of a balloon it will decrease in size. This is an example that shows that air takes up space.
- Air also exerts pressure, when you think back to the balloon example the air is exerting pressure on the inside of the balloon, this means that the air is pushing against the walls of the balloon trying to get out.
- Air pressure always moves from high to low pressure. Still using the balloon example think about what happens if you release the opening of the balloon. All the air will rush out. This is because the pressure inside the balloon is higher than in the room you are in. Air stops rushing out once it is empty, or once the pressure is equal to the air pressure in your room.
2. Provide evidence that air is a fluid and is capable of being compressed, and identify examples of these properties in everyday applications.
- To compress something basically means to squeeze or squish it. Think of the winter time when it snows and you make a snowball. You start off with a large amount of snow and squish it into your hands into a smaller ball. You have the same amount of snow as before, only now you have compressed it so that it is all closer together.
- Another example would be to take 100 students into the gym, everyone would have plenty of space to move around. If you took those same 100 students into a classroom you would have the same amount of people they would just be packed in much tighter.
- It works the same way with air. Think of a balloon filled with air, if you were to start twisting the opening of the balloon to make the space smaller you would have the same amount of air but the air particles would all be much closer together. You could also compress the air in the balloon by adding more air to the balloon.
- This shows the two main ways of compressing air:
- Keeping the same amount of air but reducing the size of container it is being held in.
- Adding more air to the container, while keeping the size of the container the same.
- Compressing air is very common. Examples include aerosol cans (like PAM or Whipped Cream) and air compressors (to pump up balls or tires)