heat transfer

Question 1

what are the 3 methods of heat transfer

Answer 1

1. conduction
2. convection
3. radiation

Question 2

what is conduction

Answer 2

method of heat transfer in solids- requires particles

Question 3

what is convection

Answer 3

method of heat transfer in liquids and gases- requires particles

Question 4

what is radiation

Answer 4

occurs in gases and vacuums- does not require particles

Question 5

demonstration of conduction

Answer 5

place an ice cube on a metal surface and an ice cube on a wooden surface

Question 6

what happens in the conduction particle and why

Answer 6

-the ice on the metal surface melts very quickly (conducting)
- the ice on the wooden surface melted slowly (insulating)

Question 7

what are insulators

Answer 7

non-metals

Question 8

conduction in insulators

Answer 8

the atoms above the heat source absorb heat energy.
this makes them vibrate more vigorously and with greater amolitude.
these vibrations pass from atom to atom, transferring heat in the form of kinetic energy
this process is slow

Question 9

describe the process of conduction in metals

Answer 9

-the ions and free electrons above the heat source absorb energy
-the ions slowly pass on heat energy through vibrations.
-the free electrons can now move much faster than before and as they move through the metal they collide with ions, passing on kinetic energy and making the ions vibrate more

Question 10

why is air a good insulator

Answer 10

gas particles are too far apart to influence each other, so evry little energy can be transferred by thus method

Question 11

describe the process of convection

Answer 11

the fluid above the heat source gets heated, expands, becomes less dense and rises. the cooler fluid flows downwards to replace it. it, in turn, gets heated and the process is reapeated

Question 12

which methods of heat transfer requires particles

Answer 12

conduction and convection

Question 13

in which type of material does conduction occur

Answer 13

solids

Question 14

what type of material are the best conductors of heat energy

Answer 14

metals

Question 15

which particle makes metals a better conductor of heat

Answer 15

free (delocalised) electrons

Question 16

why are liquids and gases poor conductors

Answer 16

their particles are spaced too far apart

Question 17

in which type of material does convection occur

Answer 17

liquids and gases

Question 18

which colour is the best emitter of infrered radiation

Answer 18

shiny silver/white

Question 19

which colour is the best absorber of infra-red radiation

Answer 19

matt black

Question 20

which colour is the worst absorber of infra-red radiation

Answer 20

shiny sliver/ white

Question 21

the hotter an object the ____ infrared radiation it gives out

Answer 21

more

Question 22

what gives out infrared radiation

Answer 22

anything above absolute zero

Question 23

if an object is hotter than its surroundings ____________________________________________

Answer 23

it will emit more than its absorbs so its temoerature will fall

Question 24

if an object is colder than its surroundings_______

Answer 24

it will absorb more than its emits so its temoerature will rise

Question 25

where does earth get infrared radiation from

Answer 25

the sun through the vacuum of space

Question 26

does infrared radiation require particles

Answer 26

no

Question 27

consequemces of global warming

Answer 27

-polar ice caps begin to melt, causing widespread flooding
-extreme weather events that can lead to droughts and floods
-reduction in argicuktural yields, which can lead to famine in some cuntries
-destruction of some habitats , which can lead to species becoming extinct
-increase in the spread of disease

Question 28

how do the features of a vacuum keep hot thungs hot and cold things cold

Answer 28

vacuum- no particles
(no conduction or convection)
sliver case (no transfer by radiation)

Question 29

how do water pannels absorb sunlight and use it to heat water

Answer 29

-the sunlight passes through a glass window and falls onto a blackened metal sheet
-the metal is in a draughr proof enclosure to minimise heat lose by convection
-the blackened metal absorbed almosy all of the energy in the sunlight and its temperaturre often rises to over 100’c
-the heat stored in the blackened metal is then transferred to water flowing in the attached pipe