8: Thermal Physics

Question 1

What is the potential energy in a gas?

Answer 1

0J

Question 2

What are the factors affecting energy required?

Answer 2

• Mass
• Material
• Temperature difference

Question 3

What is the equation for specific heat capacity?

Answer 3

Q = mcΔθ

Question 4

What is the equation for specific latent heat?

Answer 4

Q = ml

Question 5

What are the units of specific heat capacity?

Answer 5

J/kg°C or K^-1

Question 6

What is the definition of specific heat capacity?

Answer 6

Energy required to rise the temperature of 1kg of a material by 1K

Question 7

What is the definition for specific latent heat of fusion?

Answer 7

Energy required to change 1kg of a solid into 1kg of a liquid, with no change in temperature

Question 8

What is the definition for specific latent heat of vaporisation?

Answer 8

Energy required to change 1 kg of a liquid into 1 kg of gas, with no temperature change

Question 9

What is a mole?

Answer 9

A measure of the amount of atoms or molecules in a substance

Question 10

What is the equation to work out the number of moles?

Answer 10

moles = mass/Mr

Question 11

Name 5 ideal gas laws

Answer 11

• Gases are made up of a very large number of atoms in constant random motion at random speeds
• The volume occupied by the atoms themselves is entirely negligible relative to the volume of the container
• All collisions, both between the molecules themselves, and the walls of the container, are perfectly elastic
• The time of collisions of atoms with each other and the walls is negligible compared with the time between collisions
• There are no electrostatic forces between the gas molecules.

Question 12

What is Boyle’s Law?

Answer 12

For a fixed mass of gas, when temperature is constant, pressure and volume are inversely proportional

Question 13

What is Charles’ Law?

Answer 13

For a fixed mass of gas, when pressure is constant, volume is directly proportional to absolute temperature

Question 14

What is Gay-Lussac’s Law (pressure law)?

Answer 14

For a fixed mass of gas, when volume is constant, pressure is directly proportional to absolute temperature

Question 15

What is the combined gas law?

Answer 15

PV/T = k

Question 16

What is the ideal gas equation?

Answer 16

pV = nRT

Question 17

What does the n stand for in the ideal gas equation?

Answer 17

one mole of gas

Question 18

What is the molar gas constant (R)?

Answer 18

8.31 J K^-1 mol^-1

Question 19

How do you convert from degrees to Kelvins?

Answer 19

+ 273

Question 20

What is temperature?

Answer 20

How hot an object is

Question 21

What is meant by internal energy?

Answer 21

The internal energy of an object is the sum of the random distribution of the kinetic and potential energies of all its molecules

Question 22

What happens to the average kinetic energy of particles as temperature increases?

Answer 22

Increases

Question 23

What is energy like in solids?

Answer 23

• Particles held in fixed positions by strong electrostatic forces have low kinetic energy and all the potential energy is due to the strong forces
• If a solid gains energy, particles gain enough kinetic energy to break the strong electrostatic bonds, forming a liquid.

Question 24

What is energy like in liquids?

Answer 24

Particles can move further apart so have more potential energy and can move more freely so have more kinetic energy

Question 25

What is energy like in a gas?

Answer 25

Particles are moving very fast so have very high kinetic energy, they can also move far apart so they have the potential energy as well

Question 26

What can increase internal energy? (ΔU)

Answer 26

• Heating the object (ΔQ)
• Doing work on the object (ΔW)

ΔU = ΔQ + ΔW