Science Form 1

Unit 7

Heat

Part II (7.4-7.6)

APPLICATION OF EXPANSION AND

CONTRACTION OF MATTER

7.4

1. Thermometers

a. The mercury thermometer is used to measure

changes in temperature.

b. When the surrounding temperature rises, the

mercury in the thermometer expands and the mercury in the thermometer expands and the

mercury column rises and vice versa.

2. Bimetallic thermometers

a. It has a thin, coiled bimetallic strip.

b. The metals used in the bimetallic strip

are brass and iron.

c. Brass expands or contracts faster than iron.c. Brass expands or contracts faster than iron.

d. The expansion and contraction of brass which is

faster d. The expansion and contraction of brass

which is faster than iron cause the coil to curl and

show the rise or fall in temperature.

e. Bimetallic thermometer is usually used in electric

ovens and car radiators.

• Diagram of a bi-

metallic strip

showing how the

difference in difference in

thermal expansion

in the two metals

leads to a much

larger sideways

displacement of

the strip

A bi-metallic coil from a thermometer

reacts to the heat from a lighter, by

uncoiling and then coiling back up when

the lighter is removed.

Thermometers

Digital Clinical

Thermometer Bath ThermometerCar Thermometer

Thermometer

Thermo scan

Thermometer

Industrial

Equipment

Thermometer

Bath Thermometer

Bottle

Thermometer

Weather

Thermometer

Cooking

Thermometer

3. Rivets

a. Rivets are steel bolts used to fasten two metal plates

firmly together.

b. The rivet is first heated over a very strong flame and

then it is fitted into the holes in the metal plates.

c. The thin end is then flattened with a hammer. c. The thin end is then flattened with a hammer.

d. When the rivet cools down, it contracts and holds the

two metal plates tightly together.

4. Other instruments that applied the principle

of expansion and contraction of matter:

a. Axles of wheels

b. Fire alarms

c. Thermostatc. Thermostat

d. Electric Irons

e. Air conditioners

f. Gas ovens

g. Refrigerators

5. Examples of using the principle of expansion and

contraction.

a. Railway tracks with small gaps.

b. Electric cables and telephone wires hung loosely.

c. Bridges with one end fixed and the other end

rests on rollers.

d. Concrete road surfaces built in small section

or using tiles as pavement.

e. Pipelines are usually coiled and have curved e. Pipelines are usually coiled and have curved

joints

ABSORBING AND GIVING OUT HEAT

7.5

7.5 Absorbing and Giving Out Heat

1. The rate of absorption and radiation of heat by an

object depends on

a. the temperature around the object.

i. The hotter the object, i. The hotter the object,

the more heat is given

out.

ii. In the same way, the

colder the object, the

more heat it absorbs.

b. the type and colour of its surface.

i. Dark, dull objects absorb heat better than

white, shiny objects.

7.5 Absorbing and Giving Out Heat

2. When an object gives out heat, its

temperature drops.

3. In general,

a. A good radiator of heat is also a good a. A good radiator of heat is also a good

absorb of heat.

b. Dull, black surfaces are very good radiators

and absorbers of heat.

c. Shiny objects are good reflector s of heat. reflector s of heat.

Emission experiment

Four containers were filled with warm water. Which container would have the

warmest water after ten minutes?

Dull metal Shiny black

Shiny metal Dull black

The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost.

The ________ container would be the coolest because it is the best at _______ heat radiation.

shiny metalradiation

dull black

emitting

Absorption experiment

Four containers were placed equidistant from a heater. Which container would have the

warmest water after ten minutes?

Dull metal Shiny black

The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best.

The _________ container would be the coolest because it is the poorest at __________ heat radiation.

dull black

radiation

shiny metal

absorbing

Shiny metal Dull black

APPRECIATING THE BENEFITS OF HEAT

FLOW

7.6

7.6 Appreciating the Benefits of Heat Flow

1. We should appreciate the flow of heat

through the three states of matter and

vacuums.

2. Their applications make our lives more

comfortable.

1. Which of the following is not a method of heat transfer?

A. Radiation

B. InsulationB. Insulation

C. Conduction

D. Convection

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

A. Solid

B. LiquidB. Liquid

C. Gas

D. Fluid

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

A. Radiation

B. ConductionB. Conduction

C. Convection

D. Insulation

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull whiteB. Dull white

C. Shiny black

D. Dull black

5. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull whiteB. Dull white

C. Shiny black

D. Dull black