# Need help with Mass-Energy Equivalence

If mass-energy equivalence is taken into account when water is cooled to form ice, then:

Argument 1. The mass of the water should remain unchanged as the energy lost during the phase change is accounted by lowering of potential energy of the molecules of water.

Argument 2. When water is cooled to form ice, its thermal energy decreases. By mass-energy equivalence, mass should decrease.

Which one do you think is correct?

Note by Lokesh Sharma
5 years, 8 months ago

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- 5 years, 8 months ago

i think 1st one is correct... if i am wrong then please tell me why other one is right

- 5 years, 8 months ago

This question was asked in AIEEE 2002. The answer key to this question to any place I have searched so far is supporting Argument 2.

(The answer to this question is (c))

Take a look at this excerpt from Wikipedia regarding mass-energy equivalence: "E = mc2 has frequently been used as an explanation for the origin of energy in nuclear processes, but such processes can be understood as simply converting nuclear potential energy, without the need to invoke mass–energy equivalence."

So, the other way round it implies you can substitute mass-energy equivalence to explain energy released. This supports argument 2.

- 5 years, 8 months ago

plz explain...

- 5 years, 8 months ago

Explain what?

- 5 years, 8 months ago

Argument 2 is correct.

- 5 years, 8 months ago

1

- 5 years, 8 months ago