Question

air pressure is the force exerted on a surface by the weight of the air above. at high altitudes, there is less air pushing down on the earth’s surface from above than at low altitudes. this allows particles of air to spread out more. in other words, the air is less dense at high altitudes than at low altitudes.
complete the paragraph.
the base of a mountain has a

altitude and

air pressure than the top of the mountain. air at the base of the mountain has

particles in a given amount of space, so the air is

dense.

Explanation:

1. For the first blank (altitude of mountain base): The base of a mountain is at a lower altitude compared to the top. So the word is "lower".
2. For the second blank (air pressure at mountain base): Since at low altitudes air pressure is higher (more air pushing down), the base (low altitude) has higher air pressure than the top. So the word is "higher".
3. For the third blank (air particles at mountain base): At low altitudes, there are more air particles in a given space (as air is denser). So the word is "more".
4. For the fourth blank (air density at mountain base): Since there are more particles, the air is more dense. So the word is "more".

Answer:

• The base of a mountain has a $\boldsymbol{\text{lower}}$ altitude and $\boldsymbol{\text{higher}}$ air pressure than the top of the mountain. Air at the base of the mountain has $\boldsymbol{\text{more}}$ particles in a given amount of space, so the air is $\boldsymbol{\text{more}}$ dense.