How altitude affects air pressure and density.

Joe, a hiker, stands at the top of a hill on a trail above the ocean. Joe's friend Dave is just starting out at the trailhead, which is at the beach.

Which statement about this scenario is accurate?

• The air Joe is breathing is denser than the air at sea level.

• The air pressure is higher where Joe is than where Dave is.

• If Joe keeps going up, air pressure will continue to decrease.

• The air Joe is breathing is denser than the air Dave is breathing.

As altitude increases, what happens to air pressure?

• It fluctuates.

• It increases.

• It decreases.

• It stays the same.

The image shows mountains of various heights, numbered 1, 2, and 3. The plain (flat ground) is labeled number 4.

At which point is air pressure lowest?

• 1

• 2

• 3

• 4

Which phrase describes air density?

• increases as altitude increases

• equals mass divided by volume

• pushes molecules in one direction

• exerts less pressure as it increases