Why does air density decrease with increasing altitude?

Hope this helps :)

So, :) Altitude is height above sea level. The density of air decreases with height. There are two reasons that i ope will answer you question and help you first :)h: at higher altitudes, there is less air pushing down from above, and gravity is weaker farther from Earth's center. So at higher altitudes, air molecules can spread out more, and air density decreases

Explanation: