Matter: Very Simple

Question 1

What is zero Kelvin equivalent to in degrees centigrade?

Answer 1

-273°C = 0K

Question 2

What is Boyle’s Law?

Answer 2

At constant temperature the pressure and volume of a gas are inversely proportional - p ∝ 1/V

pV = Constant

Question 3

What is Charles’ Law?

Answer 3

At constant pressure, the volume of a gas is directly proportional to its absolute temperature, T.

V/T = Constant

Question 4

What is the Pressure Law?

Answer 4

At constant volume, the pressure of a gas is directly proportional to its absolute temperature, T.

p/T = Constant

Question 5

How can the gas laws be verified and what do they only apply to?

Answer 5

Via experiment.

The gas laws only apply to a fixed mass of gas.

Question 6

What is the Ideal Gas equation?

Answer 6

pV = nRT

Question 7

What is the Ideal Gas equation a good approximation for?

Answer 7

A gas at low pressure and high temperature.

Question 8

What is Avogadro’s constant?

Answer 8

6.02 x 10²³

Question 9

What is the number of particles equal to?

Answer 9

The number of moles multiplied by Avogadro’s constant.

N = nN_a

Where:

N = number of particles

n = number of moles

N_a = Avogadro’s constant

Question 10

What is Boltzmann’s costant?

Answer 10

The amount of energy required to increase the temperature of 1 particle by 1 Kelvin.

It relates particle energy to temperature.

Question 11

What is Boltzmann’s constant equivalent to?

Answer 11

The gas constant, R, divided by Avogadro’s constant, N_a.

k = R/N_a

Question 12

What is nR equivalent to?

Answer 12

Nk

Question 13

What is the Equation of State for an Ideal Gas?

Answer 13

pV = NkT

Question 14

Why is the particle velocity of an ideal gas proportional to the pressure of that gas?

Answer 14

Because the particles have a larger momentum as a result of their larger velocity, they exert a greater force upon collision. Force is proportional to pressure, therefore an increase in particle velocity increases pressure.

Question 15

Why is particle number proportional to pressure?

Answer 15

Because there are more particles, there are more collisions. This increases the average force exerted per second on the container. Force is proportional to pressure, therefore particle number is proportional to pressure.

Question 16

How is container volume related to the pressure of an ideal gas? Why is this?

Answer 16

Container volume is inversely proportional to pressure. Particles have a lesser distance to travel between collisions in a smaller container, therefore they collide more frequently with the container. This, and the fact that the surface area of the container decreases, both lend to an increase in pressure because pressure is proportional to force and inversely proportional to surface area.

Question 17

Why is it that 1/3 appears in the equation for the pressure of an ideal gas?

Answer 17

Because particles are able to move along three axis, and there is an equal likelihood that the particles will travel along each of those axis - 1/3 of the particles will be travelling along one axis, 1/3 on another, and 1/3 on the final one.

Question 18

What is the kinetic theory equation?

Answer 18

pV = 1/3 Nmc²

Where:

p = pressure

V = volume

N = Number of particles

m = mass of a particle (kg)

c²= mean square speed of a particle

Question 19

What are the simplifying assumptions of the kinetic theory of gases?

Answer 19

The gas contains a large number of particles.

The particles are rapid and random.

The particles’ motion follows Newton’s laws.

Collisions between particles are perfectly elastic.

There are no attractive forces between the particles.

Collision forces act instantaneously.

Particles have a negligible volume relative to their container.

Question 20

How far will a particle be from its starting position if it collides with another particle each time it moves 7 x 10^-8m, and makes 144 000 000 movements?

Answer 20

8.4 x 10^-5m

D = √N d

Question 21

Define specific thermal capacity.

Answer 21

The amount of energy required to increase the temperature of 1kg of a substance temperature by one kelvin.

Question 22

What is the equation which describes the energy required to increase the temperature (θ) of a substance by a given amount

Answer 22

E = mcΔθ

Where:

E = required energy

c = specific heat capacity

m = mass

Δθ = Desired temperature change

Question 23

Which is pointier, a Maxwell-Boltzmann distribution for a cool gas or a Maxwell-Boltzmann distribution for a hot gas?

Answer 23

The distribution for a cool gas it pointier.

Question 24

What happens to the average and maximum particle speed of a gas as its temperature is increased?

Answer 24

The maximum particle speed and average particle speed both increase, flattening out the Maxwell-Boltzmann distribution for the curve.

Question 25

What is internal energy equivalent to?

Answer 25

Kinetic energy + Potential energy

Question 26

What is the internal energy of an ideal gas?

Answer 26

Average particle energy (kT) x number of particles

Question 27

What is the average kinetic energy of a gaseous substance’s particles?

Answer 27

Particle number x 1/2 mc²

Where c²is the mean square velocity of the particles and m is the mass of a particle in kg.

Question 28

How is temperature linked to the internal energy of a system?

Answer 28

Temperature is proportional to average particle velocity - hotter particles have more energy (E=kT) and move more quickly. Particle velocity is, in turn, proportional to kinetic energy which is proportional to the internal energy of the system.

Question 29

Given that pV = 1/3 Nmc² and pV = nRT, what is the average kinetic energy of a particle?

Answer 29

1/2 mc² = 3/2 nRT/N