PROPERTIES OF GASESDon’t worry… they’re a breeze!

Compressibility

How much the volume of matter decreases under pressure.

High for gases; low for solids and liquids1. Gases easily compressed because of the

space between molecules/particles

2. The volume of a gas is large, but # of particles small.

B. Factors that Affect Gas Pressure

1. Amount of gas is related to gas pressure. Example: rigid container filled with helium. Volume of the gas is fixed, (size of the container

does not change)Add more gas into the container gas

pressure increases! Add LOTS? If you exceed the strength of the

container, it explodes! Remove gas from the container gas pressure

decreases

Example 2: Can of hair spray

Why does it leave when you press the button?- The gas inside the can is at a higher

pressure than the atmospheric pressure (the pressure the layers of our atmosphere puts on our earth),

- Gas flows from areas of high pressure to areas of low pressure.

- Press the button at the top of the can, the gas inside (high pressure) the can flows into the environment (low pressure), and carries with it droplets of hairspray / paint!

Factor 2: Volume ↓ volume of a container, ↑ the pressure of the gas. ↑ volume of the container, ↓ pressure the gas is under. Example: sit on an exercise ball.

Your weight “smashes” the ball, exerting pressure on the gas within.

Deep sea fish die when they’re brought to the surface of the water: ○ Evolved to withstand high pressure from all the water that “sits”

on them at the bottom of the ocean. ○ As they rise to the surface, the water pressure decreases (since

there is less water “sitting” on them near the surface). ○ The gasses in their bodies expand and cause their bladders

and vessels to explode, killing the fish.

Factor 3: Temperature ↑ in temperature will ↑ kinetic energy of the

moleculesThey move faster and collide with each other

with more force. ↑ the pressure the gas is under. ↑ the volume of the gas, (gas molecules spread

out more) Example: If you leave a bag of chips in a

warm spot, the gas inside the bag expands from an increase in temperature, causing the bag to puff up.

GAS LAWS

Law vs. Theory?

Theory: Well-tested explanation for a broad set of observations

Law: Statement that summarizes the results of many observations and experimentsDoesn’t explain the relationship it describes

Boyle’s Law

P1V1 = P2V2 Temperature Constant As pressure decreases, volume

increases

Charles’ Law

V1/T1 = V2/T2

Pressure Constant As temperature increases, volume

increases

Gay-Lussac’s Law

P1 / T1 = P2 / T2 Volume is constant As temperature increases, pressure

increases

Combined Gas Law

P1V1 / T1 = P2V2 / T2

Only the amount of a gas is constant

To do gas laws calculations, the temperature must always be in Kelvins.

Temp in Kelvin = the temp in C + 273 = ⁰temp in K