Heat transfer

Question 1

What are three was heat is transferred?

Answer 1

Radiation
Conduction
Convection

Question 2

What is heat radiation?

Answer 2

The transfer of heat energy by Infrared radiation

Question 3

What energy transfers, transfer their energy by particles?

Answer 3

Conduction

Convection

Question 4

What is the main form of heat transfer in solids?

Answer 4

Conduction

Question 5

What is the main form of heat transfer in liquids and solids?

Answer 5

Convection

Question 6

What can be emitted by liquids solids and gases?

Answer 6

Infrared Radiation

Question 7

What can absorb and emit infrared radiation?

Answer 7

Any object, whether or not conduction or convection are taking place

Question 8

The bigger the temperature difference between a body and its surroundings, the….

Answer 8

…faster energy is transferred by heating

Question 9

What is infrared radiation? (waves)

Answer 9

Emission of electromagnetic waves

Question 10

When do objects absorb and emit IR?

Answer 10

Continually

Question 11

Where is IR emitted from?

Answer 11

The surface of an object

Question 12

An object that’s hotter than its surrounding emits ….(+/-)…. radiation than it absorbs
What happens to the temperature of the object?

Answer 12

More - it cools down

Question 13

An object that’s cooler than its surrounding emits ….(+/-)…. radiation than it absorbs
What happens to the temperature of the object?

Answer 13

Less - it warms up

Question 14

The hotter an object is the more….

Answer 14

radiation it radiates in a given time

Question 15

What does radiation depend on?

Answer 15

Surface colour and texture

Question 16

What absorbs IR better than light shiny surfaces, such as glass or silver?

Answer 16

Dark, matt surfaces

Question 17

What emit more IR than shiny light surfaces?

Answer 17

Dark matt surfaces

Question 18

What do light shiny surfaces do to IR?

Answer 18

They reflect a lot of the IR falling on them

Question 19

What uses shiny light surfaces to reflect IR? How?

Answer 19

Vacuum flasks have silver inner surfaces to keep heat out or in.

Question 20

Where do solar hot water pipes run?

Answer 20

Under the black surface, or painted pipes under glass.

Question 21

How is the water in pipes in solar panels heated?

What can this water be used for?

Answer 21

Radiation from the sun is absorbed by the black surface to heat the water
Washing or to be pumped into radiators to heat the building

Question 22

Kinetic theory describes how…
Kinetic theory explains ….
The energy an object (or particle) has because of its movement is called its….

Answer 22

… particles move in solids liquids and gases
… the three states of matter
… kinetic energy

Question 23

What are the three states of matter, give examples….

Answer 23

Solid - ice
Liquid - water
Gas - water vapour

Question 24

What is the difference between particles of different state?

Answer 24

Their arrangement and energy of particles are different

Question 25

Solids: What forces hold the particles close together in a ..... ..... arrangement? How much energy do the particles have and what does this mean?

Answer 25

Strong forces of attraction, fixed regular arrangement The particles don't have much energy so they vibrate in their fixed positions

Question 26

Liquids: How strong are the forces of attraction between the particles? How are the particles arranged? They have ...... energy than particles in a solid. They move in ..... directions at ..... speeds

Answer 26

Weaker They are close together but can move past each other, they are in an irregular arrangement More Random.... low

Question 27

Gases: How much force of attraction is there between the particles? How much energy do the particles have? How do the particles move?

Answer 27

Almost none More than liquids and solids They are free to move and travel in random directions and at high speeds

Question 28

When you heat a substance you give its particles..... they then... This is what causes solids to .... and liquids to ....

Answer 28

More kinetic energy - the vibrate and move faster Solids to melt Liquids to boil

Question 29

Conduction of heat occurs in what state of particles? (s.l,g)

Answer 29

Mainly in solids

Question 30

What is the process where vibrating particles pass on their extra kinetic energy to neighboring particles

Answer 30

Conduction

Question 31

Conduction continues throughout the solid and gradually some ..... is passed all the way through the solid causing a ..... at the end of the solid. This causes an .... in the heat .... from its surface.

Answer 31

extra kinetic energy.... increase in temperature. | Increase... radiating

Question 32

Conduction is usually faster in what type of solid? | Why? (collide)

Answer 32

Denser solids | Because the particles are closer together and so will collide more often and pass energy between them

Question 33

Materials that have larger spaces between their particles conduct.... these are called ....

Answer 33

....heat energy much more slowly | Insulators

Question 34

Why are materials good conductors? why are metals so good at conducting?

Answer 34

Because of their free electrons, these are free to move inside the metal.

Question 35

How does conduction happen through a metal heated at one end? So why does conduction happen faster in a metal than another material?

Answer 35

At the hot end electrons move faster and collide with the free electrons, transferring energy, these pass on their energy to the next electron. Electrons transfer energy faster as they are free to move when atoms vibrating and passing their energy is slower

Question 36

When does convection occur in gases and liquids? | Why doesn't it occur in solids?

Answer 36

When the particles with more energy move from the hotter region to the cooler region and take their energy with them Because the particles aren't free to move about.

Question 37

How to immersion kettles and hot water tanks work?

Answer 37

By convection currents

Question 38

Describe how an immersion heater works: 1. The coils and water: 2. Particles near the coils..... 3. So the water becomes ... .... because.... 4. What happens to the hot water? 5. So the cold water is ... 6. So the cold water now gets....

Answer 38

1. Heat energy is transferred through radiation from the coils to the water 2. get more energy so move around faster 3. less dense, because there is more space between the particles so it expands 4. It's less dense so it rises above the cool water 5. Displaced as the hot water takes its place so it sinks down to the coil 6. heated by the coils and rises so you get convection currents circling the heat energy through the water.

Question 39

Where are convection currents most effective?

Answer 39

In round containers, squarish in size as tall thin ones don't allow good convection, the water can rise but an't sink.

Question 40

Convection currents are all about .....

Answer 40

changes in density

Question 41

What inside object uses convection currents? Why?

Answer 41

Radiators, the hot air the water has heated rises in the room as it's less dense so the cool dense air must sink to fall back to the radiator to heat up.