Heat Transfer

Question 1

Describe the bonding, arrangement and motion of particles in solid liquid and gases

Answer 1

Particles in a solid are bonded, close together and vibrate

Particles in a liquid and not bonded, close together and wiggle quickly

Particles in a gas are not bonded, far apart and have high kinetic energy

Question 2

Describe the kinetic energy of particles in solids, liquids and gases

Answer 2

Particles in solids have low kinetic energy

Particles in liquids have medium kinetic energy

Particles in gases have high kinetic energy

Question 3

Explain the energy transfer during condensation

Answer 3

When a liquid is formed through condensation heat is transferred to its surrounding, as a liquid is formed it provides energy to the surrounding resulting in its particles having less kinetic energy

Question 4

Explain the transfer of energy during evaporation

Answer 4

When a liquid evaporates it removes hot energy from the surrounding. As a liquid changes into a gas it takes heat energy from surroundings to give its particles more kinetic energy to become a gas

Question 5

State the factors that increase evaporation

Answer 5

Evaporation is greater at a higher temperature, high airflow and a large surface area

Question 6

State the factors that increase condensation

Answer 6

Condensation is greats when there is a high moisture content in the air and lower surface temperature

Question 7

Define specific heat capacity

Answer 7

The specific heat capacity of a substance is the amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius

Question 8

State examples of how heat can be reduced from buildings

Answer 8

Lost insulation, cavity wall insulation, draft excluders and silver foil on walls and ceilings

Question 9

Define U-values

Answer 9

U-values measure how effective a material is as an insulator. The lower the U-value the better the material is as an insulator

Question 10

What is infra-red radiation?

Answer 10

Infra-red radiation is an electromagnetic wave

Question 11

What factor increases the amount of infra-red radiation

Answer 11

The hotter a body is the more energy it ‘radiates’ as IR

Question 12

Describe how external colour affects the emission and absorption of infra-red radiation

Answer 12

Dark,Matt surfaces are good absorbers and good emitters of

Radiation. Light, shiny surfaces are poor absorbers and poor emitters of radiation

Question 13

Explain how conduction occurs in non-metals

Answer 13

Particles vibrate more when heated, this vibration is oases through bonds

Question 14

Explain how conduction occurs in metals

Answer 14

Metals are good conductors because they contain ‘free electrons’. The free electrons can ‘miss out’ atoms, transferring the heat energy quickly

Question 15

Explain how convection occurs in a gas or liquid

Answer 15

When particles in a gas or
Liquid are heated they move quicker, the gas or liquid expands, becoming less dense and rises. This produces a convection current

Question 16

Explain how the shape of an object affects heat loss

Answer 16

(For the same volume) a thin, flat object will radiate heat energy faster than a fat object, this is one reason why domestic radiators are thin and flat

Question 17

Explain how temperature difference between an object and it’s surroundings affect heat loss

Answer 17

The bigger the temperature difference between an object and it’s surroundings, the faster the rate at which heat moves