Part 1 The transfer of energy.

Question 1

what are the three types of energy transfer?

Answer 1

Conduction, convection and radiation.

Question 2

What is infra-red?

Answer 2

A form of radiation. It is not visible on the light spectrum, it is just greater than the visible end of the red light spectrum, and is a form of heat transfer.

Question 3

What is absorption?

Answer 3

Absorption is when incoming radiation is trapped (absorbed) by the object.

Question 4

What is emission?

Answer 4

Emission is when an object releases radiation (emits) it.

Question 5

what is energy transfer by heating?

Answer 5

energy transfer is the ‘energy exchange’ of one system to another. sometimes this is done through heat exchanges such as convection, radiation and convection. It always goes from hot things to cold things, there is a always a direction.

Question 6

What are U values?

Answer 6

U-values measure how effective a material is an insulator. The lower the U-value is, the better the material is as a heat insulator. For example, here are some typical U-values for building materials: a cavity wall has a U-value of 1.6 W/m². It measures how fast heat can transfer through a material. Heat transfers faster through materials with a higher U value

Question 7

How do you calculate specific heat capacity?

Answer 7

The energy= MCAT ( Mass * Capacity * temprature (AT) )

The mass is in kilograms
The capacity is J/Kg/degrees c
The temprature is degrees c

Question 8

What is heat radiation?

Answer 8

It’s the transfer of heat energy through infra-red radiation.

Question 9

What is the main source of heat transfer for convection?

Answer 9

Liquid and gases.

Question 10

What is the main source of heat transfer for Conduction?

Answer 10

Solids.

Question 11

What can emit infra-red radiation?

Answer 11

Solids, liquids or gases. Any object can both emit and absorb infra-red radiation even if convection or conduction are taking place at that time.

Question 12

How does temperature change the amount of infra-red radiation?

Answer 12

An object that’s hotter than its surroundings will emit more radiation than it absorbs (as it cools down) Where as an object that’s colder than its surroundings will absorb more radiation than it emits (as it warms up)

The hotter an object is the more radiation it will emit at a given time. You can feel the radiation if you stand near something hot like a fire.

Question 13

What does radiation depend on?

Answer 13

The colour, and texture of the surface. Dark matt surfaces absorb radiation better than light shiny surfaces. They also emit more radiation (at any given temperature) Light shiny surfaces reflect the radiation.

Question 14

What is solar thermal heating?

Answer 14

They are the solar hot water panels on top of houses. The solar hot water panels contain water pipes under a black surface (or black painted pipes under glass). The radiation from the sun is then absorbed by the black surface to heat water in the pipes which can be used for the radiators or doing the washing up.

Question 15

What is the kinetic theory?

Answer 15

The kinetic theory describes how particles move in different states of matter. Solids (e.g. ice), liquids (e.g. water) and gases (e.g. water vapour). The particle substance in each state are the same only the arrangement and energy of the particles is different.

Question 16

What are the particles in a solid like?

Answer 16

Strong forces of attraction hold the particles close together in fixed regular arrangement. The particles don’t have much energy so they can only vibrate in their fixed positions.

Question 17

What are particles in a liquid like?

Answer 17

There are weaker forces of attraction between the particles. They are close together but they can move passed each other to form irregular arrangements. They have ,more energy than the particles in a solid and they move in different directions at a low speed.

Question 18

What are the particles in gases like?

Answer 18

There is almost no force of attraction between the particles. They have more energy than in a liquid or a solid and they are free to move around and travel in random directions at high speeds.

Question 19

What happens when you heat a substance?

Answer 19

You give it more kinetic energy (KE) Which means they vibrate or move faster. This is what will eventually cause solids to melt and liquids to boil.

Question 20

What is the conduction of heat?

Answer 20

It’a when vibrating particles pass on their extra kinetic energy to their neighbouring particles. The process continues throughout the solid and and gradually some of the extra KE is passed all the way through a solid which will cause a rise in the temperature; and in the amount of heat radiating from it’s surface. Usually conduction is faster in denser objects because the particles are closer together meaning hey will collide more often.

Question 21

Why are metals good conductors?

Answer 21

Because of their free electrons.The electrons are free to move inside the metal. At the hot end the particles are closer together and so will collide with other free electrons, transferring heat which then transfers heat to other electrons, etc. Because the electrons can move freely it;s quicker at transferring the energy.

Question 22

When does convection occur?

Answer 22

It occurs when the more energetic particles move from the hotter region to the cooler region of that liquid or gas and take there heat energy with them. Heating a room with a radiator relies on convection currents. Hot,less dense air by the radiator rises and, cooler air flows to replace it.

Question 23

What is condensation?

Answer 23

It’s when a gas turns into a liquid. When a gas cools the particles slow down and loose kinetic energy which attracts them to each other, pulling them closer together, If the air temperature gets cold enough the particles get close enough so condensation takes place and the gas becomes a liquid. Water vapour in the air condenses when it comes into contact with a cold surface.

Question 24

What is evaporation?

Answer 24

Evaporation is when particles escape from a liquid and turn to a gas. Particles evaporate from a liquid at high temperatures that are much lower than the liquids boiling point. The fastest particles are most likely to evaporate from the liquid so when they do the average speed and kinetic energy of the remaining particles decreases.

Question 25

What is the rate of heat energy transfer?

Answer 25

How quickly heat energy is radiated from a surface of an object.

Question 26

What does heat energy transfer depend on?

Answer 26

The surface area (larger = more infra-red waves emitted)

The type of material etc.

Question 27

What device is designed to limit heat energy transfer?

Answer 27

Vacuum flasks. They have a double wall which prevents all conduction and convection through the sides. The walls are silver which keeps heat loss from radiation to a minimum. Supported by insulating foam (minimises heat conduction) Stopper is made from plastic and filled with cork or foam (Reduce heat conduction)

Question 28

How does your body control heat energy transfer?

Answer 28

In the cold your hairs stand up on end to trap a thicker layer of insulating air around the body; limits amount of heat loss through convection. When you’re too warm the body diverts more blood flow to the surface of the skin; heat is lost by radiation and why people turn pink when hot.

Question 29

What’s the difference between cost effectiveness and effectiveness?

Answer 29

Cost effectiveness and effectiveness are not the same; the most effective methods of insulation are the ones that give you the biggest annual savings. Eventual the money you save will equal what you invested (put in) Most cot effective = cheapest.

Question 30

Which types of heat transfers are involved in energy efficiency in the home?

Answer 30

1. Cavity wall insulation. Helps reduce heat loss by conduction.
2. Loft insulation. Helps reduce heat loss through conduction and convection.
3. Draught proofing. Helps reduce heat loss through convection
4. Hot water tank jacket. Reduces conduction and radiation
5. Thick curtains. Prevents hot air reaching window by convection. Reduces conduction

Question 31

What does specific heat energy tell you?

Answer 31

How much energy stuff can store. It will take more heat energy to increase the temperature of some things compared to others.

Question 32

What are the 9 types of energy?

Answer 32

1. Electrical (whenever a current flows)
2. Light ( from the sun, light bulb etc.)
3. Sound ( loudspeakers, anything noisy)
4. Kinetic/movement (Anything moving)
5. Nuclear ( from nuclear reactions)
6. Thermal/heat (flows; hot to cold)
7. Gravitational potential (anything that can fall)
8. Elastic potential ( Springs, elastics, etc.)
9. Chemical ( Foods, fuels, batteries, etc.)

Question 33

What are forms of stored energy?

Answer 33

Gravitational potential, Elastic potential and Chemical energy’s. Because the energy is not doing anything, it’s waiting to happen i.e waiting for it to be turned into one of the other forms.

Question 34

What 2 principle’s do all the energy’s go by?

Answer 34

Energy can be transferred usefully from one form to another, stored or dissipated but it can never be created or destroyed.

And…

Energy is only useful when converted from one form to another.