KS4 Energy - Heat Transfer

8/2/2019 KS4 Energy - Heat Transfer

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KS4 Energy - Heat Transfer


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Heat transfer

In which direction does heat move?

Heat energy always

moves from w______to c_____ areas.

armerooler


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Solids, liquids and gases

What do the particles look like in a solid, a liquid and a gas?

Liquid Gas Solid


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Conduction

When you heat a metal strip at one end, the heattravels to the other end.

As you heat the metal, the particles vibrate, thesevibrations make the adjacent particles vibrate, and so onand so on, the vibrations are passed along the metal andso is the heat. We call this?

Conduction


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Metals are different

The outer e_______ for metalatoms drift, and are free to move.

When the metal isheated, this Sea ofelectrons gain k_____energy and transfer itthroughout the metal.

Insulators, such as w___ and p____, do nothave this Sea of electrons which is why theydo not conduct heat as well as metals.

lectrons

inetic

ood lastic


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Why does metal feel colder than wood, if theyare both at the same temperature?

Metal is a conductor, wood is an insulator. Themetal conducts the heat away from your hands, thewood does not conduct the heat away from yourhands as well as the metal, so the wood feels

warmer than the metal.


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Insulating layers of air

Other uses of a trapped insulating layer of air are-

Clothing

Cavity walls

Ceiling tiles

Fibreglass

WallpaperFur coats


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Insulators

Double glazing

insulating layer of air

Double glazing keeps your

house warmer because thelayer of a__ between thepanes of glass is a poorc_______, so it acts like ani_______, it reduces heat lossby conduction from your house.

ir

onductornsulator


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Heating fluids

What happens to the particles in a liquid or agas when you heat them?

The particles spread out andbecome less dense.

This effects fluid movement.What is a fluid?A liquid or gas.


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Fluid movement

Cooler, more d____, fluidssink through w_____, lessdense fluids.

In effect warmer liquids and

gases r___ up.

Cooler liquids and gases s___.

ensearmer

ise

ink


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Water movement

Hot waterrises

Cooler

water sinks

Convection

current

Cools at the

surface


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Why is it windy at the seaside?



Cold air sinks

Where is thefreezercompartment

put in a fridge?

Freezercompartment

It is put at thetop, becausecool air sinks,

so it cools thefood on theway down.

It is warmerat thebottom, so

this warmerair rises and

a convectioncurrent is

set up.



Convection questions

Why are boilers placed beneath hot watertanks in peoples homes?

Hot water rises.

So when the boiler heats the water, and the hot waterrises, the water tank is filled with hot water.

Why does hot air rise and cold air sink?

Cool air is more dense than warm air, so thecool air falls through the warm air.



The third method of heat transfer

How does heat energy getfrom the Sun to the Earth?

There are no particlesbetween the Sun and theEarth so it CANNOTtravel by conduction or

by convection.

?RADIATION



Radiation

Radiation travels in straight lines

True/False

Radiation can travel through a vacuum

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False



Emission experiment

Four containers were filled with warm water. Whichcontainer would have the warmest water after ten minutes?

Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten

minutes because its shiny surface reflects heat _______ backinto the container so less is lost. The ________ containerwould be the coolest because it is the best at _______ heatradiation.

shiny metal

radiationdull black

emitting



Absorption experiment

Four containers were placed equidistant from a radiative heater,which container would have the warmest water after ten minutes?

The __________ container would be the warmest after tenminutes because its surface absorbs heat _______ the best.The _________ container would be the coolest because it isthe poorest at __________ heat radiation.

dull black radiationshiny metal

absorbing

Shiny metal

Dull metal

Dull black

Shiny black

R di i i



Radiation questions

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.

Why are shiny foil blankets wrapped around marathonrunners at the end of a race?

The shiny metal reflects the heat radiation from the runnerback in, this stops the runner getting cold.


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2. In which of the following arethe particles closest together?

A. Solid

B. LiquidC. Gas

D. Fluid



3. How does heat energy reachthe Earth from the Sun?

A. Radiation

B. ConductionC. Convection

D. Insulation



4. Which is the best surface forreflecting heat radiation?

A. Shiny white

B. Dull whiteC. Shiny black

D. Dull black


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5. Which is the best surface forabsorbing heat radiation?

A. Shiny white

B. Dull whiteC. Shiny black

D. Dull black

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KS4 Energy - Heat Transfer