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Do Now: According to Reference Table H, which substance has the highest vapor pressure at 75 o C?

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### Matter & Energy – GasesAim: How do gases react due to changes in temperature, pressure, and volume?

Do Now:

According to Reference Table H, which substance has the highest vapor pressure at 75oC?

HW:

Pressure & Moles

- Rigid container pump in more air
- What happens to # of collisions?
- What happens to pressure?
- Direct/indirect relationship?

Pressure & Volume

Boyle’s Law

- If container is smaller…
- What happens to…
- # of particles?
- Space between them?
- # of collisions?
- Pressure?
- Direct/Indirect relationship?

Look! A real life example!

- Bag O’Chips at the top of Waimea Canyon, Kauai, Hawaii (elev. 4000 ft)

- Same Bag O’Chips at sea level, Poipu Beach, Kauai, Hawaii

Other examples of this relationship

- SCUBA diving
- Higher pressure underwater, so lungs are compressed
- As diver rise to the surface, they must exhale – as the pressure on their bodies (and lungs) decreases, the volume of their lungs increases – the lungs could burst!
- Breathing

Pressure & Temperature

- What happens if you heat a sealed container in the microwave? (Think in terms of molecular movement)
- Joseph Gay-Lussac’s Law
- Temperature increases…
- KE of particles?
- # of collisions?
- Pressure?
- Direct/Indirect relationship?

Volume & Temperature

What happens to KE of mlcls as the T increases?

What happens to size of container (if the walls are flexible?)

Charles’ Law

Direct/Indirect relationship?

Topic: Matter & Energy - Gases

- Aim: How do you calculate changes in the conditions of a gas?
- DN: What would happen to a balloon if you filled it to capacity inside your air-conditioned home, then went outside on a 90 degree day? Why?
- HW: RB p. 69 #48-51, 57-59
- castlelearning due next MON. Write out numerical setups and answers for #1, 4, 10, 12, 13 (the calculation questions)

Combined Gas Law

- Table T
- Shows relationships among pressure, volume, and temperature, and shows what happens if P, V, or T of a gas are changed

P1V1=P2V2

T1 T2

The (1) refers to initial conditions, the (2) refers to new/final conditions

- Temp MUST be in K!!!

At a temperature of 273 K 400ml gas sample has a pressure of 101.3kPa. If the pressure is changed to 50.65kPa, at which temperature will this gas sample have a volume of 551ml?

P1V1 = P2V2

T1 T2

P1 = 101.3kPa 101.3kPa x 400ml = 50.65kPa x 551ml

V1 = 400ml 273K T2

T1 = 273K 101.3kPa x 400ml x T2 = 50.65kPa x 551ml x 273K

P2 = 50.65kPa T2 = 188K

V2 = 551ml

T2 = X

Rules…

- If a problem says that one of the factors (P, V, or T) stays constant, cross that factor out of the equation!
- Remember: Temperature must always be in Kelvin!!!!!
- If a problem mentions STP, refer to TABLE A, which has the values for the standard TEMPERATURE and PRESSURE.

A sample of sulfur gas at 50°C and a volume of 5.0L is cooled to 10°C as pressure remains constant, what is the new volume?

P1V1 = P2V2

T1 T2

P is constant, so we cross it out!

V1 = V2

T1 T2

At STP a gas has a volume of 20 L. If the pressure increases to 2 atm and the temperature decreases to 200 K, what is thenew volume?

Initial Conditions Final Conditions

P1 = 1 atm P2 = 2 atm

V1 = 20 L V2 = ?

T1 = 273 K T2 = 200 K

(Note: the T & P

values are from Table A!

We use the atm unit for

pressure b/c atm is used in

the problem, not kPa.)

A sample of gas confined to a volume of 10 L at 10oC and 2 atm is subjected to a pressure increase to 2.5 atm and a temperature decrease of 10oC. What is the new volume?

Sample Problems

- As the pressure of a gas at 2 atm is changed to 1 atm at constant temperature, the volume of the gasdecreases

increases

remains the same

- The volume of a given mass of an ideal gas at constant pressure isdirectly proportional to the Kelvin temperature.

directly proportional to the Celsius temperature.

inversely proportional to the Kelvin temperature.

inversely proportional to the Celsius temperature

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