Gases Gases

Gases are defined as having no definite volume and no definite shape.

Some properties of gases are1.They expand to fill their containers.2.They have very low densities3.They can flow/ diffuse4.They exert a pressure

What is pressure?Pressure is defined as the force exerted over an area

What are some things that have air pressure?1.Car tires2.Beach balls3.Inflatable jumpers4.Helium balloons

What is pressure?Pressure is defined as the force exerted over an area

What are some things that have air pressure?1.Car tires2.Beach balls3.Inflatable jumpers4.Helium balloons5.Hot air balloons

If size stays the same, the pressure outside is equal to the pressure inside. (yellow)If the size decreases, the pressure outside is greater than the pressure inside. (blue)If the size increases, the pressure outside is less than the pressure inside.

Before the balloon is Before the balloon is blown upblown up

all the outside air is pushing on the balloon.

(no inside air to push back = flat as a pancake)

Let’s try to draw those pressures…

But, after the balloon But, after the balloon is blown upis blown up

air outside is pushing “in” AND, air inside is pushing “out”

Since the balloon stays the same size, the pressure (pushing) inside the balloon MUST be the same as the pressure outside the balloon.

What about after the What about after the vacuum pump?vacuum pump?

Air inside is pushing more (has greater air pressure)

than the air outside so it allows the balloon to expand!

What two variables are What two variables are changing?changing?

Since the pressure outside decreased, the volume (size) of the balloon increased.