The statement that 'heat cannot flow by itself from a body at a lower temperature to a body at a higher temperature', is known as
- A.Zeroth law of thermodynamics
- B.First law of thermodynamics
- C.Second law of thermodynamics
- D.Third law of thermodynamics
Correct answer
Explanation
The correct answer is C, Second law of thermodynamics. This is the Clausius statement of the second law.
Rudolf Clausius stated that heat cannot by itself pass from a colder body to a hotter one; work must be done to make it do so. That is why a refrigerator or an air conditioner needs electricity to pump heat out of a cold space into the warmer room. Another form, the Kelvin-Planck statement, says no engine can turn all the heat it takes in into work. The second law also gives the idea of entropy and sets the direction in which natural processes run.
A is wrong: the zeroth law says that two bodies each in thermal equilibrium with a third are in equilibrium with each other, which is the basis of the thermometer. B is wrong: the first law is the conservation of energy, heat supplied equals the rise in internal energy plus work done. D is wrong: the third law says the entropy of a perfect crystal becomes zero at absolute zero.
Exam tip: Zeroth law, temperature; first law, energy conservation; second law, direction of heat flow and entropy; third law, absolute zero.
Practice Questions
View allThe valency of phosphorus is
- 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 ?
- A.Single celled eukaryotes belong to Kingdom Protista
- 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
- A.larger than osmotic pressure
- B.smaller than osmotic pressure
- C.equal to osmotic pressure
- D.equal to atmospheric pressure
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Only a pressure greater than the osmotic pressure of seawater can push pure water backwards through the membrane. In ordinary osmosis, water moves through a semipermeable membrane from the dilute side to the concentrated side.
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.
Read the full explanation →The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of
- 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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