14 : Thermal Physics

Question 1

Absolute temperature

Answer 1

A temperature value relative to absolute zero

Question 2

Absolute zero

Answer 2

The lowest possible temperature of a system, where no heat remains and the particles have no kinetic energy (-273K)

Question 3

Change of phase

Answer 3

The transitions between solids, liquids and gases. during a change of phase, there is a change of internal energy but not temperature

Question 4

Gas

Answer 4

• A phase of matter in which the particles are high energy and free to move.
• Will fill the space they are placed in.
• negligible electrostatic force between them
• EPE =0

Question 5

Liquid

Answer 5

• A phase of matter in which the particles can slide over each other, but still have forces of attraction between each other
• more KE than solids

Question 6

Solid

Answer 6

• A phase of matter in which the particles can only vibrate about fixed positions
• due to strong intermolecular forces

Question 7

Specific heat capacity

Answer 7

The amount of energy required to increase the temperature of 1kg of a substance by 1 Kelvin

Question 8

Specific Latent heat

Answer 8

the amount of energy required to change the state of 1kg of a substance without a change in temperature

Question 9

Thermal equilibrium

Answer 9

A stable state in which there is no thermal heat transfer between two regions

Question 10

Internal energy

Answer 10

The sum of the randomly distributed kinetic and potential energies of the particles in a given system

Question 11

Changes in internal energy when changing state

Answer 11

• no change in kinetic energy
• the temperature is constant during melting
  -the potential energy of the molecules increases during molecules as electrostatic forces break and molecules move apart
• therefore the internal energy increases

Question 12

Changes in internal energy when temperature if object increases

Answer 12

• temperature increases therefore kinetic energy increases
• molecules are moving faster
• internal energy has increased
• electrostatic energy is constant

Question 13

Describe the motion of the atoms in a metal heater in water

Answer 13

• The atoms of the metal vibrate about fixed positions
• the water molecules have translational kinetic energy
• the motion of the water molecules is random
• the metal atoms and water molecules have the same kinetic energy

Question 14

Why is electrostatic potential energy negative

Answer 14

Energy must be supplied to break the intermolecular bonds