Expansion and Contraction

When the liquid level in a thermometer moves up, its _______ changes.

• colour

• mass

• volume

Answer explanation

When the liquid in the thermometer gains heat, it expands.

the liquid takes up more space = the liquid has greater volume

However, this does not affect the liquid's mass as the amount of

matter remains the same. No liquid was added nor removed from

the thermometer.

Also, the colour is unaffected.

The liquid in the tube moves up because it _______ heat ______ the hot water.

• gained, to

• gained, from

• lost, to

• lost, from

Answer explanation

The liquid moved up because it had gained heat from the hot water.

gain = get something

Hence, it must be paired with the preposition 'from'

lost = give away something

Hence, it must be paired with the preposition 'to'

Nate observed that the drop of coloured ink in the glass tube dropped.

What is the correct explanation for this observation?

• The air in the flask gained heat from the ice and took up more space.

• The air in the flask lost heat to the ice and took up less space.

• The ice gained heat from the drop of ink and melted.

• The ice lost heat to the air in the flask and melted.

Answer explanation

Besides the drop of coloured ink, there is air in the flask.

Hence, for the ink to move down, the air in the flask had lost heat to

the ice and contracted.

The red balloon is inflated because it gained heat and expanded.

The yellow balloon is deflated because it lost heat and contracted.

True or false?

• True

• False

Answer explanation

The explanation is not accurate because the balloon would not have inflated

if not for the air inside taking up more space and stretching the balloon.

What is the correct method to get the ink drop to move to the left?

• Add hot water to both basins X and Y.

• Add hot water to basin X and cold water to basin Y.

• Add cold water to basin X and hot water to basin Y.

• Add cold water to both basins X and Y.

Answer explanation

Since we want the drop of ink to move to the left, we have to get the air in the flask on the side of basin Y to expand and the air in the flask on the side of basin X to contract.

Two glasses are stacked tightly together.

Which action will help to separate them?

• Pour cold water into the top glass.

• Pour hot water into the top glass.

• Immerse the bottom glass into cold water.

Answer explanation

To separate the glasses, we need the glass on top to contract and/ or the

glass below to expand.

Rachel tried to put the ball through the ring but it would not fit.

What should she do to get the ball through the ring?

• Heat the ball over a flame.

• Heat the chain over a flame.

• Heat the ring over a flame.

• Heat the ball, chain and ring over a flame.

Answer explanation

This is not the usual question we encounter during our experiment.

I hope you were not tricked.

In this case, the metal ball is too big. Hence, we either have to make the ball

lose heat and contract or make the ring gain heat and expand.

Qi Zhen noticed that electric cables were hung loosely between posts.

What is the correct reason for this?

• To prevent the cables from breaking on a cold day.

• To prevent the cables from breaking on a hot day.

• To ensure that there is room for the cables to expand on a hot day.

Answer explanation

If the cables were hung taut, the cables would snap on a cold day

as matter loses heat and contracts. (gets shorter)

Hence, they are designed to hang loosely.

To ensure that the gap between railway tracks is enough, builders should measure the _______.

• contraction on the hottest day

• contraction on the coldest day

• expansion on the coldest day

• expansion on the hottest day

Answer explanation

The gap left between tracks is designed to leave room for expansion.

Hence, the builders should check the maximum expansion and this would

take place on the hottest day.

A brass strip and a steel strip of similar size were joined as one.

Then it was heated for a period of time until it bent.

Which diagram shows how the joined strip would look when cooled down for the same period of time?

• 
• 
• 

Answer explanation

Since the brass strip expanded more than the steel strip, it would follow

that the brass strip would similarly contract more than the steel strip when cooled for a period of time.

Hence, the brass strip would be shorter and the joined strip would curve upwards with the brass on the inner arc.