Thermal Physics

Question 1

Define absolute zero

Answer 1

The temperature at which particles have no kinetic energy and the volume and pressure of a gas are zero

Question 2

State Boyles Law

Answer 2

For a fixed mass of ideal gas at constant temperature the pressure is inversely proportional to the volume

Question 3

State Charles Law

Answer 3

For a fixed mass of ideal gas at a constant pressure the volume is directly proportional to absolute temperature

Question 4

State the pressure law

Answer 4

For a fixed mass of ideal gas at constant volume the pressure is directly proportional to the temperature

Question 5

Define an ideal gas

Answer 5

A gas which obeys the 3 gas laws at all temperatures and pressures and cannot be liquefied (Collisions are all elastic and no intermolecular forces)

Question 6

Define a mole of a substance

Answer 6

An amount of substance containing 6.02 x 10^23 particles

Question 7

Define molar mass

Answer 7

The mass of one mole of a substance

Question 8

What is Brownian motion

Answer 8

The random motion of particles in a fluid caused by the collisions with surrounding particles

Question 9

Define pressure

Answer 9

The force per unit cross-sectional area

Question 10

What causes pressure

Answer 10

Molecules applying a force to a surface

Question 11

What is isobaric pressure

Answer 11

Constant pressure

Question 12

What do the letters in pV=nRT represent

Answer 12

p = pressure
V = volume
n = number of moles
R = molar gas constant
T = temp in kelvin

Question 13

What equation represents moles, molar mass and mass

Answer 13

m = nM
mass = number of moles x molar mass

Question 14

What happens to normal gas molecules

Answer 14

They undergo collisions with other particles, move at different speeds and move unpredictably randomly

Question 15

Explain the increase of pressure when a gas is heated or compressed

Answer 15

Pressure is due to particles applying a force against a surface. This occurs at random. When a particle hits a surface there is a change in momentum

Question 16

What happens in a system if the temp increases but the volume is constant?

Answer 16

Molecules travel faster so mean kinetic energy of molecules increase, momentum of the molecules increases, impacts are harder and more frequent, each collision transfers more momentums, more force per unit area on surfaces and therefore more pressure. So if temp increases, the pressure increases and the volume stays constant

Question 17

What are the assumptions for an ideal gas?

Answer 17

• All molecules are identical
• Molecules move randomly
• Newtonian mechanics apply
• Volume of the gas molecules is negligible
• No intermolecular (electrostatic or gravitational) forces apply
• Collisions are all elastic and kinetic energy is conserved
• Molecules move in a straight line at constant velocity

Question 18

What equation links all three laws

Answer 18

P₁V₁/T₁ = P₂V₂/T₂

Question 19

Do ideal gases have potential energy?

Answer 19

No since there are no intermolecular forces

Question 20

What equation do we use for internal energy of an ideal gas?

Answer 20

3/2 nRT

Question 21

How do you convert moles to number of molecules

Answer 21

Multiple moles by the Avogadro constant

Question 22

hi

Answer 22

hi :)