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Answer is B. 

For set up B, when the air in the bottle warms up, it expands and will rise, filling the balloon, increasing the mass and volume of air in the balloon.

For set up C, opposite happens, the air in the bottle cools and contracts, creating space in the bottle, therefore air from outside will be sucked into the balloon to fill the space in the bottle cause of the pressure difference caused by the air in the bottle contracting, hence increasing the volume and mass of air in the balloon.

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Thanks, Jennifer.
What happens in setup A? Will the baloon melt in 100 deg water?

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Just to reply to your question, answering Science questions require you to understand which topic, eg. heat, light, systems, etc. 

In this question, the concepts tested are : 

  • heat -> matter expansion
  • Matter occupies space
  • Concept of mass vs volume

So to answer the question, you should not be thinking about balloon melting, etc. 

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Thanks, Zappy for your advice. I came across the following wuestion:

A 50-kg wooden crate of 1 m height, 1 m length and 1 m breadth was placed on a cart. The cart was pulled around a bend at a high speed without toppling. Another wooden crate of the same size and weight was placed on top of the first crate. The cart was pulled at the same speed around a bend. This time, the cart and its two crates overturned.

A double decker bus has 50 seats on the lower deck and 30 seats on the upper deck. If all the seats were taken up, passengers would be allowed to stand. The bus rule states that standing passengers are allowed only on the lower deck.

Question: why are standing passengers not allowed on the upper deck?

Which primary school topic is tested here? How to answer this?

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This question is showing the results of an experiment and the applying the results to a theoretical situation.


Proposed ans: 

The experiment showed that the higher the crates are placed on a trolley, the less stable it is  around a corner at high speed. If a double decker bus has standing passengers on the upper deck, the weight of the higher passengers will cause the bus to be unstable when cornering at higher speeds and may cause the bus to topple. Hence, passengers are not allowed on the upper deck of a double decker bus.

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Many thanks, Zappy. Like the way you phrased the answer, very logical & clear.

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That’ll depend on the quality of the ballon haha.

But in set up A the important thing is that the balloon is tied, hence no air can either go in or escape. Theoretically, yes, the air in the balloon will expand being heated up by the water hence volume will increase, but since no air can go in or escape, the mass of the air inside will not change, therefore not satisfying Jen’s conclusion. This is unlike set up B where the air is also heated up, just that this time it’s the air in the bottle which is able to rise and fill the balloon.

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