Charles Law

Charles's & Boyle's Laws

by Mrs. Bennett

​Charles's Law: Volume and Temperature are DIRECTLY RELATED

​Charles’s law or the law of volumes is an ideal gas law that states that the volume and temperature of a fixed amount of gas are proportional at constant pressure. Doubling the temperature of a gas doubles its volume. Halving the temperature of a gas halves its volume. The law takes its name from French scientist Jacques Charles, who formulated the law in the 1780s.

​Charles's Law Examples

​The official rules of the NFL require footballs to be inflated to a gauge pressure between 12.5 to 13.5 pounds per square inch. The rules do not specify the temperature at which such measurement is to be made. Thus, if a football were inflated to the minimum pressure of 12.5 psi at room temperature, the pressure would drop below the minimum as the gases inside cooled to a colder temperature on the playing field.

AFC Playoff Game Results​

New England Patriots: 45

​Indianapolis Colts: 7

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​Outside Temperature: 52*F

​Charles's Law Examples

• ​Car tires have lower PSI during the winter

• ​Deodorant spray bottle warning labels: "pressurized container, protect it from sunlight. Do not expose to temperature exceeding 50°C”

• ​Hot Air Balloon-when the gas is heated, it expands, and becomes less dense and the balloon is lifted in the air. The warm is less dense than the cold air, which means that it is lighter than the cold air. Also, the warm air has less mass per unit volume

Multiple Choice

If temperature decreases, volume ________

Think: What could happen to a balloon when it's taken outside on a cold day?

• increases/gets bigger

• decreases/gets smaller

• stays the same

Multiple Choice

What is the relationship between temperature and volume?

• related: if one goes up, the other goes up

• inversely related: if one goes up, the other goes down

​Boyle's Law-PRESSURE AND VOLUME

​Volume and pressure have an INVERSE RELATIONSHIP.

​

​If pressure increases, volume decreases (gas is compressed).

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​If pressure decreases, volume increases (gas is released/expands)

​Boyle's Law Examples

• Bike pump: When you pump air into a tire, the gas molecules inside the tire get compressed and packed closer together. This increases the pressure of the gas, and it starts to push against the walls of the tire. You can feel how the tire becomes pressurized and tighter.

• Soda Bottles: To get carbon dioxide gas into the liquid, the whole bottle is usually pressurized with gas. As long as the bottle is closed, it is very hard to squeeze, as the gas is confined to a small space and pushes against the bottle's walls. When you remove the cap, however, the available volume increases and some of the gas escapes. At the same time its pressure decreases.

​Boyle's Law Formula

P1 X V1=​ P2 X V2

​

​P=pressure

​V=volume

​*Temperature must be constant

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​A 200mL can of spray with a pressure of 20kPA is run over by a car and flattened to a volume of 10 mL. What is the new pressure? Should it be greater or less than the initial 20kPA (kilo Pascal)?

20 X 200 = ___ X 10

Multiple Choice

What is the relationship between volume and pressure?

• directly related: if one goes up, the other goes up too

• inversely related: if one goes up, the other goes down

• no relationship

Multiple Choice

If volume increases, the pressure __________

• increases

• decreases

• stays the same