Heating and Cooling

Question 1

what is temperature?

Answer 1

how hot or cold something is

Question 2

what does heat energy do?

Answer 2

it moves from high temperature areas to low temperature areas.

Question 3

what happens in conduction in solids?

Answer 3

the particles with more heat energy vibrate quickly. because the particles are close together, movement gets passed along to the particles.

Question 4

why is air a poor conductor?

Answer 4

particles in a gas are spread out. most of the time they are not connected. this means air is a poor conductor because the particles cannot pass the heat energy on easily

Question 5

what is heat measured in?

Answer 5

joules (J)

Question 6

why does a metal handlebar feel colder than a plastic seat on a bike?

Answer 6

the metal of the handlebars is a good conductor. it is colder than your hand so heat energy flows from your hand when you touch the metal. the flow of heat energy makes your hand feel cold.

the plastic seat is not such a good conductor so it feels a lot warmer when you touch it.

Question 7

what happens in a boiling kettle// convection in a kettle

Answer 7

• the heating element of a kettle heats the water around it
• the particles in the hot water move faster and further apart
• the hot water is less dense than the cold water around it. so the hot water rises up through the cold water
• cold water replaces the hot water around the heating element and starts to heat up

Question 8

what is a convection current?

Answer 8

hot air is less dense than cold air, so it rises up around the wall heater. the cold air moves to replace it.

Question 9

how long does heat energy take to travel from the sun to earth?

Answer 9

8 minutes

Question 10

what reflects heat?

Answer 10

shiny objects or white objects

Question 11

what absorbs heat energy?

Answer 11

dull and dark objects

Question 12

what are some ways to insulate your house?

Answer 12

• loft insulation
• double glazed windows
• draught excluders
• radiator reflectors and cavity wall insulation

Question 13

how does a thermos flask keep things hot?

Answer 13

there are no particles in a vacuum so conduction and convection cannot happen. the shiny surface reflects most radiation. the surface in the flask reflects back the small amount of radiation that reaches it.

the stopper is also filled with plastic foam, which contains trapped air to make it a poor conductor

Question 14

what is evaporation?

Answer 14

as you heat up water, some of the faster particles start to escape from the surface.

Question 15

what is boiling?

Answer 15

when you heat water so that bubbles of evaporated water form everywhere in the body of the water.

Question 16

what is condensation?

Answer 16

once water boils, the particles seperate and form a gas. steam at 100C has a lot more energy than water at 100C.

if you cool water vapour or steam down it changes back to water.

the steam that emerges from a kettle or a steam iron is visible because it is beginning to condense