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Compressibility  How much the volume of matter decreases under pressure.  High for gases; low for solids and liquids 1. 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 molecules They 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.

Law vs. Theory?  Theory: Well-tested explanation for a broad set of observations  Law: Statement that summarizes the results of many observations and experiments Doesn’t explain the relationship it describes

Boyle’s Law  P 1 V 1 = P 2 V 2  Temperature Constant  As pressure decreases, volume increases

Charles’ Law  V 1 /T 1 = V 2 /T 2  Pressure Constant  As temperature increases, volume increases

Gay-Lussac’s Law  P 1 / T 1 = P 2 / T 2  Volume is constant  As temperature increases, pressure increases

Combined Gas Law  P 1 V 1 / T 1 = P 2 V 2 / T 2  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 ⁰ C = temp in K