If barometric pressure is down, what happens to the molecules?

If barometric pressure is down, what happens to the molecules?

• A. They are more spread out
• B. They become more dense
• C. They become heavier
• D. They remain unchanged

Answer: (A)

When barometric pressure drops, the air becomes less dense and the molecules are farther apart. Pressure comes from how often molecules collide with surfaces; with fewer collisions in a given area, the gas expands and the average distance between molecules increases. The mass of the molecules doesn’t change, so they don’t become heavier, and they don’t stay the same density. The result is that the molecules are more spread out.

When barometric pressure drops, the air becomes less dense and the molecules are farther apart. Pressure comes from how often molecules collide with surfaces; with fewer collisions in a given area, the gas expands and the average distance between molecules increases. The mass of the molecules doesn’t change, so they don’t become heavier, and they don’t stay the same density. The result is that the molecules are more spread out.