Why is it difficult to measure the coefficient of expansion of a liquid than solid?
- A.Liquids tend to evaporate at all temperatures
- B.Liquids conduct more heat
- C.Liquids expand too much when heated
- D.Their containers also expand when heated
Correct answer
Explanation
The correct answer is D, Their containers also expand when heated. A liquid has no shape of its own, so it must be measured inside a vessel that expands at the same time.
A solid rod can be heated and its own length measured directly. A liquid can only be heated in a container, and the container expands too. What we see is the apparent expansion, the liquid's real expansion minus the expansion of the vessel. To get the real expansion, the expansion of the vessel must be added back: the coefficient of real expansion equals the coefficient of apparent expansion plus the volume coefficient of the container. This is why, when a flask of water is first heated, the level may dip slightly before it rises.
A is wrong: evaporation can be prevented by closing the vessel and is not the main difficulty. B is wrong: most liquids are poor conductors of heat, and conduction has no bearing on measuring expansion. C is wrong: a large expansion would make measurement easier, not harder.
Exam tip: For liquids, real expansion = apparent expansion + expansion of the vessel; liquids have only volume expansion.
Practice Questions
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- A.2, 3
- B.3, 4
- C.4, 5
- D.3, 5
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Phosphorus has five electrons in its outer shell and shows two common valencies, 3 and 5. Phosphorus, atomic number 15, has the electronic configuration 2, 8, 5.
Read the full explanation →Which one of the following statements is NOT correct ?
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- B.Yeast, a fungus is multicellular
- C.The fungi constitute a unique kingdom of heterotrophs
- D.Ascomycetes, a saprophytic fungi is multicellular or rarely unicellular
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This statement is false, because yeast is one of the few fungi that are unicellular. In Whittaker's five-kingdom system, fungi form a separate kingdom.
Read the full explanation →Desalination of seawater is done by using reverse osmosis. The pressure applied to the solution is
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- B.smaller than osmotic pressure
- C.equal to osmotic pressure
- D.equal to atmospheric pressure
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Read the full explanation →Which one of the following does not form oxide on reaction with oxygen?
- A.Magnesium
- B.Lead
- C.Tin
- D.Silver
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Silver sits near the bottom of the reactivity series and does not combine with oxygen even when heated in air.
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- A.urea into sulphur dioxide
- B.sugar into carbon dioxide
- C.lipids into methane
- D.urea into ammonia
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Bacteria on the floor break down the urea in urine and release ammonia, which has a sharp, pungent smell. Urea, CO(NH2)2, is the main nitrogenous waste of humans.
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