Heat

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Slide 1

Heat 1st year

Slide 2

By the end of this chapter you will be able to

Describe heat energy, its’ units and explain how it converts to other forms

Explain how heat affects expansion and contraction of materials

Explain conduction, convection and radiation

Identify good and bad conductors of heat (insulators V conductors)

Differentiate between heat energy and temperature

Slide 3

What is Heat?

Form of energy because it can move things

- E.g: Makes a hot air balloon rise.

- Steam engines

Measured in JOULES (J)

Slide 4

Heat can be converted to other forms of energy

Sunlight (heat) is used by plants for Photosynthesis (to make food), it is converted to chemical energy.

Oil and gas are burned in power stations to produce heat energy, this is used to turn turbines which produce electricity (electrical energy)

Slide 5

How is heat produced?

The movement of particles/molecules produces heat

Particles move about more and take

up more room if heated – this is why

things expand if heated

It is also why substances change form when heated

solids liquids gases

Slide 6

Heat Transfer

Heat always moves from a warmer place to a cooler place.

Hot objects in a cooler room will cool to room temperature.e.g: tea, coffee

Cold objects in a warmer room will heat up to room temperature.e.g: butter, ice

Slide 7

What do you think?

Slide 8

Forms of Heat Transfer

3 types;

Conduction

Convection

Radiation

Slide 9

Radiation

How does heat energy get from the Sun to the Earth?

There are no particles between the Sun and the Earth so it MUST travel by radiation

?

RADIATION

Slide 10

Radiation

The transfer of heat in rays, from a hot object, without needing a medium to pass through

It travels in all directions from a hot object

The hotter an object is, the more heat it will radiate out

Does the surface affect the way heat is radiated?

Slide 11

What colour should we paint radiators? Which colour is better to wear on a sunny day? black or white?