Question

If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should (a) Increase (b) Remain unchanged (c) Decrease (d) First increase then decrease

Answer 1

The connection between mass and energy in a system's rest frame, when the two quantities differ only by a constant and the units of measurement, is known as mass–energy equivalence in physics. The famous formula of physicist Albert Einstein describes the idea.

Complete answer:
$E=m{{c}^{2}}$
The energy E of a particle in its rest frame is defined as the product of mass (m) and the speed of light squared (${{c}^{2}}$). The formula suggests that a tiny quantity of rest mass equates to a huge amount of energy, which is irrespective of the composition of the matter, because the speed of light is a big number in common terms (about $3\times {{10}^{8}}$ metres per second). The mass of a system at rest, also known as rest mass or invariant mass, is measured. Even at high speeds approaching the speed of light, it is a fundamental physical characteristic that is independent of momentum (i.e., its value is the same in all inertial frames of reference).
The reaction in question is not a nuclear reaction in which mass and energy are exchanged. Only a phase shift occurs here, and energy in one form transforms into another. During phase transitions, mass is preserved. As a result, the water mass will stay unaltered. The mass-energy equivalence states that both mass and energy are preserved. Water loses energy when it cools to become ice, therefore a shift in energy increases the mass of water.

Hence option b is correct.

Note:
The equivalence principle states that when energy is lost in chemical processes, nuclear reactions, and other energy transformations, a comparable quantity of mass is lost in the system. Radiant energy, such as light, or thermal energy may be discharged into the environment to liberate energy and mass. Many branches of physics, including nuclear and particle physics, are founded on this idea.