P1 - Heat Transfer

Question 1

What are the 3 ways that heat energy can be transferred?

Answer 1

Radiation, conduction and convection

Question 2

What is heat radiation?

Answer 2

The transfer of heat energy by infrared radiation

Question 3

Which states of matter does conduction occur in?

Answer 3

Solids

Question 4

Which states of matter does convection occur in?

Answer 4

Liquids and gases

Question 5

How does temperature difference affect transfer of energy by heating?

Answer 5

The larger the temperature difference between a body and its surroundings, the faster energy is transferred by heating

Question 6

How does surface area affect infrared radiation?

Answer 6

The larger the surface area, the higher the rate of infrared radiation because there are more places that the waves are emitted from

Question 7

In terms of heat radiation, what happens when an object is hotter than its surroundings?

Answer 7

The object emits more radiation than it absorbes as it cools

Question 8

In terms of heat radiation, what happens when the object is cooler than its surroundings?

Answer 8

It absorbs more radiation than it emits as it warms up

Question 9

How does the surface type of the object affect its radiation?

Answer 9

Dark, matte surfaces absorb and emit much more infrared radiation than shiny, light surfaces

Question 10

Why don’t shiny, light surfaces absorb as much infrared radiation?

Answer 10

They reflect off most of the waves

Question 11

Describe how solar hot water panels make use of our knowledge of surface types and radiation

Answer 11

They contains water pipes under a black surface to heat the water in the pipes

Radiation from the Sun is absorbed by the black surface to heat the water in the pipes

Question 11

Describe the arrangement, forces and energy in solids

Answer 11

Strong forces of attraction hold the particles in a fixed regular arrangement

The particles don’t have much energy so that can only vibrate about their fixed positions

Question 12

Describe the arrangement, forces and energy in liquids

Answer 12

The forces of attraction are weaker so the particles are still close together but they can move past each other

The particles have more energy than in a solid so they move in random directions at low speeds

Question 13

Describe the arrangement, forces and energy in gases

Answer 13

Almost no forces of attraction

Particles have more energy than in liquids and solids and are free to move in random directions at high speeds

Question 14

What happens to the particles of an object when you heat it?

Answer 14

The particles get more kinetic energy and vibrate or move faster

Question 15

What is conduction?

Answer 15

The process where vibrating particles pass on their extra kinetic energy to neighbouring particles

This causes heat to spread throughout a solid

Question 16

What factor affects the rate of conduction?

Answer 16

If the particles are closer together, the particles will collide more often and the rate of conduction will be higher

Question 17

What makes a material an insulator?

Answer 17

When the material has larger spaces between its particles

Question 18

What causes metals to be good conductors?

Answer 18

Their free electrons can easily collide with each other and pass on the kinetic energy

Question 19

What is kinetic theory?

Answer 19

The theory that describes how particles move in solids, liquids and gases and tells us that the energy of a particle is its movement or vibration (kinetic energy)

Question 20

What is convection?

Answer 20

The process where more energetic particles move from the hotter region to the cooler region and take their heat energy with them

Question 21

Describe the convection in an immersion heater

Answer 21

Heat is transferred from the heater coils to the water by conduction (particle collisions)

The particles near the coils get more energy so they move around faster meaning there is more distance between them meaning that this water becomes less dense

The hotter water rises because it is less dense and displaced the colder water out of the way towards the heater coils

The cold water is heated by the coils and the hot water cools at the top of the immersion heater

This circuit repeats over and over again

Question 22

What is a convection current?

Answer 22

The way that, in convection, the hot water rises becomes cold and sinks and heats again and this circuits repeats again and again

Question 23

How does surface area affect the rate of heat energy transfer?

Answer 23

Heat is radiated from the surface of an object so the larger the surface area, the more infrared waves can be emitted from the object

Question 24

How does volume affect rate of heat energy transfer?

Answer 24

If 2 objects at the same temperature have the same surface area but different volumes, the object with the smaller volume will cool quicker

This is because a higher proportion of the object will be in contact with its surroundings

Question 25

How does the type of material affect the rate of heat energy transfer?

Answer 25

Conductors transfer heat much faster than insulators

If an object is in contact with a conductor, the heat will be conducted away much faster than if the object was in contact with an insulator

Question 26

How do vaccum flasks prevent heat transfer?

Answer 26

The glass bottle is double-walled with a vaccum between the 2 walls preventing all conduction and convectiom through the sides

The bottle is supported with insulating foam minimising conduction to or from the outer glass bottle

The stopper is made of plastic and filled with cork or foam to reduce heat conduction

Question 27

What is the simplest way that animals have evolved to deal with heat transfer?

Answer 27

Arctic foxes have small ears to prevent heat loss by radiation

Desert foxes have large ears that allow them to easily lose heat to keep them cool