Q14
1 markMCQSection A

Assertion (A): In the process of nuclear fission, the amount of nuclear energy generated by the fission of an atom of uranium is so tremendous that it produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

Reason (R): The nucleus of a heavy atom such as uranium, when bombarded with low energy neutrons, splits apart into lighter nuclei. The mass difference between the original nucleus and the product nuclei gets converted to tremendous energy.


Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

Energy Flow and Sources of Energy

Options

(0)Both A and R are true and R is correct explanation of the Assertion.
(1)Both A and R are true but R is not the correct explanation of the Assertion.
(2)A is true but R is false.
(3)A is false but R is true.
Official Answer

Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). The fission of a single uranium atom produces about 10 million times the energy released by burning a single carbon atom from coal because the nuclear force involved is much stronger than chemical bonds, and the mass defect (Δm\Delta m) is converted directly into energy according to Einstein's equation E=Δmc2E = \Delta m c^2.

nuclear fissionuraniummass differencemass defectcombustion of carbontremendous energy

Marking Scheme

  • 11 Mark for selecting Option A and explaining the mass-energy conversion mechanism.

Hint

Recall Einstein's mass-energy equivalence equation E=Δmc2E = \Delta m c^2 and how nuclear forces compare to chemical bonds.

Quick Oral Answer

Nuclear fission produces millions of times more energy than chemical combustion because a small amount of mass is converted directly into energy during the splitting of a heavy nucleus, governed by E=Δmc2E = \Delta m c^2.

Analysis & Explanation

  • Assertion (A) is True: The energy released during the nuclear fission of a single uranium atom is indeed about 10710^7 (10 million) times greater than the chemical energy released by the combustion of a single carbon atom from coal.
  • Reason (R) is True: Nuclear fission involves bombarding a heavy nucleus (like 235U^{235}\text{U}) with low-energy neutrons, causing it to split into lighter nuclei. The sum of the masses of the product nuclei is slightly less than the mass of the original reactant nucleus. This mass difference (mass defect, Δm\Delta m) is converted into energy according to E=Δmc2E = \Delta m c^2.
  • Explanation: Since the conversion of mass defect into energy is the exact physical mechanism that produces this massive amount of energy, Reason (R) is the correct explanation of Assertion (A).

Common Mistakes

  1. 1Thinking that chemical combustion and nuclear fission release comparable amounts of energy.
  2. 2Failing to link the mass defect directly to the energy output.

Interesting Facts

Just 1 gram of Uranium-235 can produce as much energy as burning approximately 3 tons of coal, highlighting the incredible density of nuclear energy compared to chemical energy.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 1 mark in the CBSE Class 10 Science 2020 examination.

What topic does this question cover in Science?

This question covers the topic "Energy Flow and Sources of Energy" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2020 paper.