# Heat Transfer

OP31 carry out simple experiments to show the transfer of heat energy by conduction, convection and radiation; investigate conduction and convection in water

These methods of transferring heat can be demonstrated using a ball as the heat and people as the particles of the matter.

Conduction is when heat travels from one particle to another. Heat moves through solids by conduction.

Convection when liquid or gas particles take extra energy and move with that energy.

Radiation is when energy is transferred in straight lines from a source of energy to other bodies

Conduction the ball moves from person to person showing how heat energy is passed from particle to particle

Convection the ball is carried by a single person

Radiation the ball is kicked or thrown to another person

Conduction

If i gave you a glass of water, but it was plastic would you know that i lied?

When you touch and hold metals how does that feel, hot of cold ??

Conduction is when heat travels from one particle to another. Heat moves through solids by conduction.

Each particle in the solid vibrates more when it is heated, this extra vibration shake the particles next to it, thus the particles share their heat.

Each particle passes on the heat energy to the particle next to it.

An experiment to show conduction in metals

Method

Stick a thumb tack to the end of each of a number of different metal rods

Place the rods in some heated water

The pin that falls off 1st is considered to be on the metal that is the best conductor, the pin that falls off last is considered the worse conductor.

Alternative method

Place equal blocks of ice on different surfaces in the same room, different containers, see which one melts the quickest

Convection

## In Liquids and gases the major method of transfer of heat is Convection. This is where the molecules move and deliver their heat energy some place else. They heat up, the molecules gain kinetic energy and the vibrate more vigorously, this makes them bigger but the mass has not changed, therefore their density goes down, therefore they float towards the top.

to demonstrate convection in Liquids

take 2 bottles, fill one with clean cold water, fill the other with warm < 50oC water with a colour, both bottles to the brim.

Steady the warm bottle, cover the cold bottle with some thin rigid plastic or card,

Place the cold bottle on top of the warm bottle, remove the card,

secure the bottles

observe

Convection Apparatus,

only add the dye after the liquid has been heated for a while

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apparatus

2 tins, one black & one shiny,

Method

Take the 2 tins, fill them with equal amounts of water

Place them in bright light

Monitor the temperature of both tins of water over time.

Other experiment

fill both up with hot water,

monitor the cooling temperature

Black object vs shiny / white objects

## Black objects absorbs heat.

White objects or shiny objects reflect heat.

## what do you notice about the temperatures?

draw a graph of the temperatures falling over time

what can you conclude ?

or use a spot light

shine it on the cans and again observe the temperatures over time.

Other exp

Glass and the sun's rays.

Glass, Thermometers.

Four sheets of glass arranged like a glasshouse.

Place one thermometer under glass and one outside.

Record temps.

Every 40 mins.

for 1 school day.

Tabulate

Graph.

Insulation

Insulation is a materials ability to keep heat from transferring,

http://conceptcartoons.com/images/subway/snow_quest.png