Energy and Temperature

Question 1

What is specific heat capacity

Answer 1

It is the amount of energy needed to raise the temperature of 1kg of substance by 1°C

Question 2

Give the equation that relates eneegy transferred and specific heat capacity.

Answer 2

ΔE=mcΔθ

Change in termal energy (J)=mass(kg)×cpecific heat capacity(J/kg°C)×temperature change(°C)

Question 3

What is temperature?

Answer 3

Temperatureis a measure of the averagekinetic energyof theparticlesin a substance.

Question 4

What two commonly scales do you know?

Answer 4

degrees Celsius (°C)

kelvin (K)

Question 5

What is specific latent heat?

Answer 5

The specific latent heat of a substance is the amount of energy needed to change the state of 1 kg of the substance without changing its temperature

Question 6

What two latent heats do you know?

Answer 6

Each substance has two specific latent heats:

latent heat of fusion (the amount of energy needed tofreezeormeltthe substance at its melting point)

latent heat of vaporisation (the amount of energy needed toevaporateorcondensethe substance at its boiling point)

Question 7

Calculating thermal energy changes

Answer 7

E= mL

thermal energy for a change in state = mass × specific latent heat

Question 8

What is Endothermic reactions?

Answer 8

Endothermicphase changes absorb heat from the environment. (They are cooling processes.)

Question 9

What is Exothermic reactions?

Answer 9

Exothermicphase changes release heat to the environment. (They are warming processes.)

Question 10

How can heat be transffered?

Answer 10

Heat can be transferred byconduction, convectionandradiation. It is only transferred from hotter things to cooler things

Question 11

Why is the heat transffered?

Answer 11

Heat is transferred in order to equalise the temperatures of the object and its environment

Question 12

Give examples of heat transfer.

Answer 12

A cup of coffee will cool down because it is giving out heat energy into the surroundings

A cold drinks can(taken out of the fridge) will warm up because it is taking in heat energy from the surroundings

Question 13

How the heat is transfered when the substance get hotter?

Answer 13

Atomsin a substance are always vibrating.If the substance gets hotter, the atoms vibrate more. The heat energy is given to the atoms, which makes them move about faster
Every time they collide with another atom, the heat energy is transferred. This is how heat travels through asolid

Question 14

What is conductor?

Answer 14

a conductor is an object or type of material that allows the flow of charge in one or more directions

Question 15

How the heat is transfered in solids and gas?

Answer 15

Solids are better than liquids. Gases are very poorconductors

Question 16

What is the best conductor?

Answer 16

Metals

Question 17

What is convection?

Answer 17

convection,process by which heat is transferred by movement of a heated fluid such as air or water

Question 18

How does convection current work?

Answer 18

In a hot fluid (gas or liquid) the particles have more kinetic energy so they move more. They spread out and the fluid becomes less dense. The hot fluid rises above the denser cold fluid forming aconvection current

Question 19

What is radiation

Answer 19

Radiation isenergy that comes from a source and travels through space at the speed of light

Question 20

What is insulation?

Answer 20

When we insulate our homes we reduce the heat lost, we use less fuel and it costs less. Still air is a good insulator, so materials with air trapped in them are often used

Question 21

How can insulate your home?

Answer 21

In cavity walls the air gap between the walls stops conduction.

In cavity wall insulation the cavity is filled with foam or mineral wool.

Loft insulation using layers of fibreglass or mineral wool

Reflective foil on walls reflects infrared radiation.

Draught-proofing stops hot air leaving and cold air entering the house.