Chap. 2: Particles of Matter

Question 1

Boyle’s Law

Answer 1

Inversely proportional.

P₁V₁ = P₂V₂

• As volume decreases, pressure increases.
• As volume increases, pressure decreases.

Example:

A balloon filling with air, or a tire filling with air.

Question 2

A gas has a volume of 125 mL of a pressure of 62.5 torr.

What is the pressure if we decrease the volume to 115 mL?

Answer 2

125 mL DECREASES to 115 mL (volume 1 decrease to volume 2), therefore pressure increases. This means it’s inversely proportional.

P₁V₁ = P₂V₂

_{Boyle’s Law}

P₁ = 62.5 torr

V₁ = 125 mL

P₂ = x

V₂ = 115 mL

We are trying to find P₂, therefore:

Question 3

Charles’s Law

Answer 3

Directly proportional.

V₁T₂ = V₂T₁

• The volume of a gas increases as its temperature increases.
• The volume of a gas decreases as its temperature decreases.

Example:

Simon inflates two balloons. He heats up one of the balloons over boiling water and puts the other balloon in the freezer. The heated balloon expanded while the freezing balloon shrank in size.

Question 4

A balloon has a volume of 325 mL at 17°C.

What is the temperature if the volume increases to 392 mL?

Answer 4

* Temperature MUST BE IN KELVIN *

V₁ = 325 mL

T₁ = 17ºC = 17ºC + 273 = 290 K

V₂ = 392 mL

T₂ = x

We are trying to find T₂, therefore:

Question 5

Gay-Lussac’s Law

Answer 5

Directly proportional.

This gas law gives the relationship between PRESSURE and TEMPERATURE when VOLUME and AMOUNT are held constant.

• If the temperature is increased, the pressure increases.
• If the temperature is decreased, the pressure decreases.

Example:

Suppose the temperature inside a container is increased. This means gas molecules will move faster and they will impact the container walls more often. This means the gas pressure inside the container will increase, since the container has rigid walls (volume stays constant).

Gay-Lussac’s Law is a direct mathematical relationship. This means there are two connected values and when one goes up, the other also increases.