Unit 5- Gases

Question 1

Properties of a gas

Answer 1

• No definite shape or volume (uniformly fills any container, exerts pressure on surroundings, volume changes with temperature and pressure)
• Mixes completely with other gases
• Much less dense than solids and liquids

Question 2

What “causes” pressure?

Answer 2

Gas pressure is a result of the constant movement of the gas molecules and their collisions with the surfaces around them

Question 3

What factors does the pressure of a gas depend on?

Answer 3

• The number of gas particles in a given volume
• The volume of the container
• The average speed of the gas particles

Question 4

Pressure equation

Answer 4

• Force / unit area
• P=F/A

Question 5

Atmospheric pressure

Answer 5

Pressure exerted due to gravity acting on air above Earth’s surface

Question 6

Meaurement of Pressure

Answer 6

• Barometer: measures atmospheric pressure
• As atmospheric pressure increases, the liquid moves up into the evacuated tube, as atmospheric pressure decreases, the liquid moves down into the pool

Question 7

Boyle’s Law

Answer 7

• Gases are compressible
• At constant T and n (temp and moles): P and V are inversely proportional
• So, Volume decreases pressure increases (and visa versa)

P1V1=P2V2

Question 8

Charles’ Law

Answer 8

• Volume of a gas extrapolates to zero at absolute zero Kelvin
• At constant P and n: V and T are proportional, so as temperature increases, volume increases

V1 / T1 = V2 / T2

Question 9

Avogadro’s Law

Answer 9

• Equal volumes of gases contain the same number of moles
• At constant P and T: V and n are proportional
• So, volume increases as moles increases

V1 / n1 = V2 / n2

Question 10

Amontons’ Law (aka Gay-Lussac’s Law)

Answer 10

• Pressure of a gas increases as the temperature of the gas increases
• At consant V and n: P and T are proportional, so as temperature increases, pressure increases