CHAPTER 7HEAT

7.1 HEAT AS A FORM OF ENERGY

7.1 HEAT AS A FORM OF

ENERGY

7.2 HEAT FLOW

7.3 EFFECT OF HEAT ON

MATTER7.4

APPLICATION OF

EXPANSION CONTRACTI

ON

7.5 HEAT ABSORBTIO

N & RELEASE

7.6 BENEFITS OF HEAT

FLOW

CHAPTER 7 HEAT

Heat is a form of ENERGY (can be used to do work)

Heat cause objects to become hotExample :

We feel hot under the sun

We feel cold when the sun is not not shining

SOURCES OF HEAT

1. Frictionrubbing two hands

together2. Combustion /burning

burning of candles3. Electricity

rice cooker

A thermal infrared image of a pencil after being sharpened (left) and of hot brakes in a car (right). Notice the hot tip of the pencil.

Energy from friction creates heat. For example when you rub your hands, sharpen a pencil, make a skid mark with your bike, or use the brakes on your car, friction generates heat

FRICTION

A thermal infrared image of a hair dryer and a flourescent light bulb

ELECTRICITY

COMBUSTION/BURNING

When a substance is burned , heat is also released

Burning firewood

USES OF HEAT IN DAILY LIFE

1. Cooking2. Drying clothes3. Keep us warm4. Causes breeze

(sea breeze & land breeze)

5. Solar energy6. Preserving food

HEAT& TEMPERATURE

Temperature is not energy, but a measure of it. Heat is energy.

Temperature – a measure of the degree of hotness of an object or substance

Unit for temperature – degree Celsius / 0C

HEAT TEMPERATURE

A form of energy

Degree of hotness of object

Heat can do work

Temperature cannot do work

Unit : Joule Unit : Celsius/Kelvin

Travels from hot to cold area

Increase when movement of particles increase

Figure 1 shows three beakers W, X, and Y containing different amount of water.

Figure 1Which of the following shows the quantities of heat in ascending order?A W, X, YB Y, X, W

C X, W, Y D Y, W, X

Figure 2 below shows an experiment on heat conduction through a piece of iron rod.

Figure 2

Which of the following thumbtacks will fall first?A. P C. RB. Q D. S

HEAT ENERGY

A hot object has more heatA cold object has less heat

Sun – primary source of heat energy

Other source of heat?1. Frictionrubbing two hands together

2. Combustion /burningburning of candles

3. Electricityrice cooker

Uses

1 2

345

1. Cooking2. Drying

clothes3. Keep us

warm4. Causes

breeze5. Solar

energy

Heat vs TemperatureHEAT TEMPERATURE

A form of energy

Degree of hotness of object

Heat can do work

Temperature cannot do work

Unit : Joule Unit : Celsius/Kelvin

Travels from hot to cold area

Increase when movement of particles increase