Which phrases describe air density? check all that apply. 1. increases as altitude increases 2. equals mass divided by volume 3. pushes molecules in one direction 4. exerts more pressure as it increases 5. measures how tightly molecules are packed

The answers are 2, 4 and 5. On the contrary to choice 1, air density decreases with altitude. Some gases have denser than others meaning they have more mass per unit volume. Temperature and pressure also have an influence on air density.

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint

gag reflex, poor dentition, gum retraction

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