High to low

The idea

Air moves from a region of higher pressure to a region of lower pressure until the pressures become equal; differences in air pressure make winds blow.

Two balloons

A big inflated balloon is joined by a tube to a small, less inflated balloon. The tube is opened.

What happens to the air in the tube?

• It moves from the big balloon to the small one
• It moves from the small balloon to the big one
• It does not move

Open the tube

Press Next step to follow the air.

Until they are equal

Air kept moving as long as one balloon had a higher air pressure than the other. When both pressures became equal, the flow stopped. Differences in air pressure make winds blow.

Air moves from a region of high pressure to a region of low pressure until the pressures become equal.

Notes

Air moves from high pressure to low pressure until the pressures are equal.

Check yourself

Air moves from a region of …

The air flow between the two balloons stops when …

Air escapes from a bicycle tube with a puncture because the pressure inside is …

What makes winds blow?

• low pressure to high pressure. Air moves from high pressure to low pressure.
• high pressure to low pressure — correct. Yes!
• one place to another with no pressure difference. A pressure difference makes the air move.
• the big balloon bursts. The flow stops when the pressures are equal.
• the small balloon is empty. Both balloons end almost the same size when the pressures are equal.
• the pressures in both become equal — correct. Yes!
• higher than outside — correct. Yes!
• lower than outside. Air flows from high to low pressure, so the inside pressure is higher.
• the same as outside. If it were the same, the air would not move out.
• Differences in colour. Differences in air pressure make winds blow.
• Differences in air pressure — correct. Yes!
• Nothing, wind is not related to pressure. Differences in air pressure cause winds to blow.