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JEE Main202120 Jul 2021Morning ShiftChemistrySolid StateActual

Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R . Assertion A : Sharp glass edge becomes smooth on heating it up to its melting point. Reason R : The viscosity of glass decreases on melting. Choose the most appropriate answer from the options given below.

Options

  1. AA is true but R is false
  2. BBoth A and R are true but R is NOT the correct explanation of A .
  3. CA is false but R is true.
  4. DBoth A and R are true and R is the correct explanation of A .

Correct answer

B. Both A and R are true but R is NOT the correct explanation of A .

Step-by-step solution

Sharp glass edges are heated to make them smooth. Because on heating glass melts and the surface of the liquid tends to take the rounded shape at the edges which has minimum surface area. This is called fire polishing of glass. Correct explanation for this is surface tension.

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