Lesson 15

Pressure and Number Density

The number of molecules in a gas is directly related to the pressure.

When the gas pressure increases, this means that there was an increase in the number of gas molecules per unit of volume.

• Number of gas molecules is represented by the letter n.

Formula: P=k(n/V)
Number Density- the number of gas particles per unit of volume which can be found by dividing the number of molecules by the volume - n/V

You can determine the pressure by measuring the difference in height of a liquid.

Practice Problems

1) decrease in air pressure with increasing altitude comes from the fact that the number density of molecules in the air decreases with the rises in altitude, ultimately lowering the gas pressure. 

6) a. B has the least air pressure because even though it has the same numbe of molecules as A, it's volume is larger making it less pressure per liter. 

A has the next largest pressure because even though it's volume is the same as C, there are fewer molecules, giving it a lower number density. 

C has the largest gas pressure because it is the small volume with the most molecules, giving it the highest number density, so a higher pressure. 

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