Which phrases describe air density? Check all that apply.1. increases as altitude increases2. equals mass divided by volume3. pushes molecules in one direction4. exerts more pressure as it increases5. 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 t have more mass per unit volume. Temperature and pressure also have an influence on air density.