EXPANSION and CONTRACTION OF MATERIALS

EXPANSION and CONTRACTION OF MATERIALS

Applying the principle of expansion and contraction of materials

Multiple Choice

REVISE...

When heated, material _____

• expands

• contracts

Multiple Choice

Heated materials expands because it _____

• lose heat

• gains heat

THE IMPORTANCE OF EXPANSION AND CONTRACTION PRINCIPLE OF MATERIALS

Knowing the principle of expansion and contraction enables us to apply it in our daily life.

During a hot day...

Multiple Choice

What would happen to the level of liquid in the thermometer if put under the hot sun?

• The level increases

• The level decreases

• No change

Multiple Choice

Give reason for your answer.

• The liquid gains heat and expands.

• The liquid lose heat and expands.

• The liquid gains heat and contracts.

The effect of heat on matter can cause the material to undergo expansion or contraction.

Kesan haba ke atas bahan boleh menyebabkan bahan mengalami pengembangan atau pengecutan.

• Example 1- During day time, solid can expand under hot Sun.

• Example 2 - During night time solid contracts because the surrounding is colder.

Gaps between connectors on a metal bridge

There are gaps between metal connectors on the bridges. The gaps allow bridges to expand when the temperature of the surrounding increases during a hot day.

Open Ended

What will happen if there's no gaps between the metal connectors?

Type your answer.

This will happen..

If there's no gaps, there'll be no room for the metal to expand during hot day. This situation can damage the other parts of the bridge.

Gaps between connectors railway tracks

The gaps between the connectors on a railway track allow the track to expand when the surrounding temperature increases.

Open Ended

What will happen if there's no gap between the connectors on the railway tracks? Type your answer.

This will happen..

If two railway tracks are laid together without any gap between them they will push against each other when they expand in the day time because of the heat of the sun.

When they cool down in the night they will contract and return to their original state pulling against each other.

Electric cables are hung loosely (sagging)

The cables are hung loosely between the poles to allow the cables to contract when the temperature decreases at night.

Open Ended

What if the electric cables are hung tightly between the poles? Type your answer.

This will happen..

If the cables are hung tightly, it will break when it contracts at night because of the decrease in the surrounding temperature.

Poll

If the principle of expansion and contraction of materials does not apply to the metal bridge, railway tracks and electric cables, what would the situation be?

Jika prinsip pengembangan dan pengecutan tidak digunakan dalam jambatan besi, landasan keretapi dan kabel elektrik, apakah keadaan yang terjadi?

• dangerous

• everything is fine

• still ok

• the material needs repair

  bahan perlu dibaik pulih

Other applications of expansion and contraction of material

Multiple Choice

Which of these DOES NOT apply expansion and contraction of material principle?

Multiple Choice

What principle do you apply to separate two glasses that stuck together?

• expansion of material

• contraction of material

• expansion and contraction of material

• heat gain and heat lose

Multiple Choice

What is the purpose of gaps between the pavement blocks?

• to allow contraction during night time

  untuk membolehkan pengecutan pada waktu malam

• to allow expansion during hot days

  untuk membolehkan pengembangan pada hari panas

• to beautify the pavement

  untuk mencantikkan laluan pejalan kaki

Poll

How do find today's lesson?

• I don't understand

• I understand

• Something new for me

Open Ended

A dented ping pong ball can be made round again by immersing the ball in hot water. Explain why.

Take your time to think and type your answer.