Heat And Engergy Part 1

Question 1

What do all objects emit? What happens when the object is hotter?

Answer 1

Infra radiation. When the object is hotter the more infra red it emits.

Question 2

What are light and shiny surfaces best at?

Answer 2

At reflecting thermal radiation

Question 3

What are dark and matt surfaces best at?

Answer 3

At emitting and adsorbing thermal radiation

Question 4

What is the best conductor of heat and why? What energy does it transfer?

Answer 4

Metal because they have free electrons which diffuse (spread out) and collide with other free electrons and ions. In this way it transfers kinetic energy.

Question 5

What materials are good insulators and why?

Answer 5

Wool and fibreglass because they contain air trapped between the fibres.

Question 6

What materials are poor conductors and why?

Answer 6

Wool and fibreglass because they have no free electrons.

Question 7

What is convection? What is it caused by? How is it created?

Answer 7

Convection is the circulation of a fluid. It is caused by heat. It is created when hot,less dense fluid rises and cold, denser fluid sinks.

Question 8

Explain how a flask works…

Answer 8

It keeps liquids warm because of the way its designed. The vacuum between the walls reduces heat transfer by conduction and convection. The silvered inner surface reduce heat transfer by radiation.

Question 9

What are all the names of the energy changes? (9)

Answer 9

Chemical energy, kinetic energy, gravitational potential energy, elastic potential energy, electrical energy, light energy, sound energy, heat energy, nuclear energy

Question 10

Can energy be created or destroyed ? Give an example

Answer 10

No. When an object falls, its gravitational potential energy decreases and its kinetic energy increases. This is the conservation of energy.

Question 11

What is useful and wasted energy?

Answer 11

Useful energy is in the form we need it. Wasted energy is not useful.

Question 12

What is the sankey diagram used for?

Answer 12

It is used to represent the energy transfers in a devise

Question 13

What happens to both useful and wasted energy when it is transferred to its surroundings ?

Answer 13

It becomes warmer

Question 14

What is energy measured in?

Answer 14

Joules

Question 15

How is efficiency calculated?

Answer 15

Efficiency(%) = (useful energy transferred/ total energy supplied) x 100
Or
Efficiency(%) = ( useful power output/ total power input) x 100

Question 16

What is the maximum machine efficiency?

Answer 16

100%

Question 17

How can efficiency be improved?

Answer 17

By reducing friction, reducing electrical resistance etc.

Question 18

What is 1kW

Answer 18

1000W

Question 19

Explain the process of conduction through metals

Answer 19

In the metal there are free electrons. It gains kinetic energy. It transfers energy into ions and it helps tranfers energy.

Question 20

Why is a matt black pot better than a shiny one?

Answer 20

Because it absorbs heat NOT LIGHT

Question 21

What is thermal (infra-red) radiation and what can it travel through?

Answer 21

Electromagnetic radiation and it can travel though a vacuum.

Question 22

What is conduction?

Answer 22

It is when heat energy can move through a substance

Question 23

What is an insulator?

Answer 23

They are poor conductors of heat?

Question 24

What is thermal radiation?

Answer 24

It is what all objects give out and take in

Question 25

What is Infrared radiation?

Answer 25

It is the same as thermal radiation which is what all objects give out and take in

Question 26

What does emit mean?

Answer 26

It means to give off.

Question 27

What is electromagnetic radiation?

Answer 27

Its the light things u learnt last year

Question 28

What does radiation mean?

Answer 28

It is an energy that comes from a source and travels through some material or space.

Question 29

What does heat transfer mean?

Answer 29

It is the movement of thermal energy from one thing to another thing of different temperatures.