Energy Transfer by Heating

Question 1

If there is an temperature difference between two objects, is the energy transferred from the cooler object to the hotter object?

Answer 1

No - the energy is passed from the hotter to the cooler one - i.e. the hotter one will cool down and the cooler one will heat up.

Question 2

What do we call the end of this energy transfer, when they are both the same temperature?

Answer 2

thermal equilibrium

Question 3

Name 3 methods of thermal energy transfer

Answer 3

Conduction, Radiation, Convection

Question 4

Energy transfer by convection can take place in fluids, what states of matter can be described as fluids?

Answer 4

Liquids and Gases

Question 5

Fill in the missing words:
L______ and gases are F_______ because they can be made to f___ The particles in these fluids can move from place to place. C_________ occurs when p_______ with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

Answer 5

LIQUIDS and gases are FLUIDS because they can be made to FLOW. The particles in these fluids can move from place to place. CONVECTION occurs when PARTICLES with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

Question 6

Do liquids and gases expand or contract when they are heated? And why?

Answer 6

Expand. The particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.

Question 7

Do liquids and gases become more or less dense when they are heated?

Answer 7

Less dense.

Question 8

Do less dense areas of a fluid sink or rise? What happens to the colder, more dense areas of fluid?

Answer 8

Rise. The colder fluid sinks.

Question 9

What do we call the movement of the fluid due to convection?

Answer 9

Convection current.

Question 10

Can you think of some examples of convection currents?

Answer 10

lava lamp, houses hotter upstairs, weather and ocean currents.

Question 11

When an object is heated, the particles in the object vibrate more - they gain energy in their what?

Answer 11

Kinetic energy stores

Question 12

What type of heat energy transfer is described here?

vibrating particles pass on their extra energy to neighbouring particles.

Answer 12

Conduction

Question 13

Why type of energy transfer requires the objects to be touching, so that the particles can bump into each other?

Answer 13

Conduction

Question 14

Are the particles in a hotter object vibrating faster or slower that in a colder object?

Answer 14

Faster

Question 15

When a hotter object touches a cooler object, what happens?

Answer 15

Energy is transferred from the hotter object to the cooler object. The hotter object looses energy and cools. The cooler object gains energy and heats up.

Question 16

What do we call the transfer of energy via invisible waves?

Answer 16

Radiation

Question 17

Can all objects radiate energy?

Answer 17

Yes

Question 18

Does an object radiate more energy when it is hotter or colder?

Answer 18

Hotter.

Question 19

Do objects need to touch to transfer energy via radiation?

Answer 19

No

Question 20

If two potatoes are near each other but not touching, and one is hotter than the other what will happen?

Answer 20

The hotter potato radiates more energy than the cold potato and so it radiates more than it absorbs and cools. The cold potato will absorb more than it radiates and so will heat up.

Question 21

Do insulators slow down or speed up the rate of energy transfer?

Answer 21

Slow down.

Question 22

Do all materials transfer energy at the same rate?

Answer 22

No

Question 23

Objects made from conductors or insulators transfer energy more quickly?

Answer 23

conductors.

Question 24

What materials are usually considered good conductors?

Answer 24

Metals

Question 25

Objects made from what materials are usually considered good insulators?

Answer 25

plastics

Question 26

What happens if you wrap a conductor in an insulator, e.g. a plastic coated pan handle?

Answer 26

The insulator slows down the rate of energy transfer to and from surrounding objects.

Question 27

Can you explain why cardboard sleeves are often used on thin plastic take away coffee cups?

Answer 27

To slow down the energy transfer from the hot drink and allow you to hold the drink comfortably.

Question 28

Can you fill in the missing words in the Principle below:
The Principle of C__________ of Energy: Energy can never be C______ or D_______ - it’s only ever T________ from one S_____ to another.

Answer 28

The Principle of CONSERVATION of Energy: Energy can never be CREATED or DESTROYED - it’s only ever TRANSFERRED from one STORE to another.

Question 29

Are most energy transfers perfect, i.e. no energy lost?

Answer 29

No

Question 30

How is energy usually lost when transferring it in useful machines?

Answer 30

Heating

Question 31

Fill in the missing words:

Total Energy I_____ = The U______ Energy + The W______ Energy

Answer 31

Total Energy INPUT = The USEFUL Energy + The WASTED Energy