UPSC Prelims 2002 · General Studies

Question 143: Science and Technology

Assertion (A): With the increase of temperature, the viscosity of glycerine increases. Reason (R): Rise of temperature increases kinetic energy of molecules.

aBoth A and R are individually true and R is the correct explanation of A

bBoth A and R are individually true but R is not a correct explanation of A

cA is true but R is false

dA is false but R is true

AnswerThe answer is (d).

Assertion A is false: the viscosity of liquids such as glycerine falls as temperature rises, because the molecules gain energy and overcome the attraction between them more easily (gases show the opposite trend). Reason R is true: a rise of temperature increases the kinetic energy of molecules. So A is false and R is true.

A. The viscosity of glycerine decreases as temperature rises.
R. A rise in temperature increases the kinetic energy of molecules.

How you could have got this

If you were sure statement 1 is not correct, only (d) is left: every other option says it is correct.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) A is false, so both cannot be true.
(b) A is false, so both cannot be true.
(c) A is false, not true.
(d) Right: A is false and R is true.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.