Question

Which statements correctly describe the properties of air? Select three options.

Air has mass but no weight.
Air pressure is created by the weight of the atmosphere pushing on Earth’s surface.
Pressure is a measure of how tightly molecules are packed.
Denser air is heavier than less dense air.
Air is less dense at higher altitudes.

Answer 1

Correct choices:
- Air pressure is created by the weight of the atmosphere pushing on Earth’s surface.
- Denser air is heavier than less dense air.
- Air is less dense at higher altitudes.

Notes:
- Air has both mass and weight (weight = mass × gravity), so the first statement is false.
- "Pressure is a measure of how tightly molecules are packed" describes density more precisely; pressure is force per unit area from molecular impacts and depends on both how many molecules and their motion (temperature).