Thermal Physics

Question 1

Thermal Equilibrium

Answer 1

Two substances in physical contact with each other no longer exchange any heat energy and both reach an equal temperature. There is no longer thermal energy transfer between the regions

Question 2

Triple Point

Answer 2

The temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium

Question 3

Zeroth Law

Answer 3

this law states if two objects are each in thermal equilibrium with a third, then all three are in thermal equilibrium with each other.

Question 4

Absolute scale of temperature

Answer 4

This can be also called the thermodynamic temperature scale which uses the triple point of pure water and absolute zero as its fixed points

Question 5

absolute zero

Answer 5

the lowest possible temperature (-273 degrees/0K) where KE is zero and volume and pressure of gas are 0. The internal energy is minimum but not 0 because it still has electrostatic potential energy stored between the particles

Question 6

SI base unit of temperature

Answer 6

Kelvin (T= theta + 273)

Question 7

Kinetic Model

Answer 7

This describes how all substances are made up of atoms or molecules which are arranged differently depending on the phase of the substance

Question 8

brownian motion

Answer 8

random motion of smoke particles visible under a microscope

Question 9

Internal energy

Answer 9

the sum of randomly distributed kinetic and potential energies of atoms or molecules within the substance

Question 10

How the internal energy of a body will increase

Answer 10

increasing the temperature will increases the average kinetic energy of the molecules or atoms inside the body

Question 11

what factors affect internal energy

Answer 11

• temperature
• change of state (solid to liquid, electrostatic potential energy increases)

Question 12

Electrostatic potential energies at different phases of a substance?

Answer 12

GAS- electrostatic potential energy is 0 as there are no negligible electrical forces between atoms or molecules

LIQUID- the electrostatic forces between atoms or molecules give the electrostatic potential a negative value. this means energy must be supplied to break the bonds

SOLID- the electrostatic forces between atoms or molecules are very large, so electrostatic potential energy has a large negative value

Question 13

what happens to temperature during change of phase

Answer 13

Temperature is constant

Question 14

specific heat capacity

Answer 14

energy required per unit mass to change the temperature by 1K

Question 15

equation for specific heat capacity

Answer 15

c=E/M*(change in temperature)

Question 16

Determing specific heat capacity

Answer 16

simple experiment using an electrical heater can be used to determine c of a solid or a liquid. The energy transfered from the heater to the substance is given by E=IVt (I is the current in the heater, V is the potential difference across the heater and t is the time taken to increase the temperature). so C=IVt/M(change in temperature). plot on graph temperature against time and the specific heat capacity is equal to p/mgradient

Question 17

specific latent heat of a substance

Answer 17

the energy require to change the phase per unit mass while at a constant temperature (L=E/m)

Question 18

specific latent heat of fusion

Answer 18

the energy required for the substance to change from solid to liquid

Question 19

specific latent heat of fusion method explantion

Answer 19

-substance at its melting point requires energy to change phase from solid to liquid
-the energy transfered to the substance increases the internal energy of substance with temperature staying constant

Question 19

specific latent heat of vaporisation

Answer 19

the energy required for the substance to change state from liquid to gas

Question 20

experiment to determine the latent heat of fusion

Answer 20

• heating circuit to be used
• thermometer to be used to ensure ice is at its melting point and ice should not be melting until the heater is switched on
• measure the potential difference across the heater, the current in the heater and the time during which the heater is used. energy transfered to the ice from the heater is equal to VIt
• measure the mass of the substance
  Latent heat of fusion=IVt/m

Question 21

experiment to measure the latent heat of vaporistaion

Answer 21

• electric heater to be used with a condenser to collect and then measure the mass of liquid that changes phase
  -=IVt/m