Question

Which best describes the second law of thermodynamics? energy is not created nor destroyed, but it can change into matter. energy is not created nor destroyed, but it can change from one energy form to another. energy can be created from matter or used to produce matter. some useful energy is lost as heat whenever an energy transfer occurs. energy transfers are always 100% efficient in changing energy from one useful form to another?

Answer 1

Answer:

Some useful energy is lost as heat whenever an energy transfer occurs.

Explanation:

When heat is converted into useful work then in that case some of the energy is transferred from high temperature reservoir to low temperature reservoir this energy transfer is always counted as heat loss.

So here we can say that

$Q_{in} = W + Q_{out}$

here we can say that heat is transferred from high temperature reservoir to some useful work with some of the energy is transferred to low temperature reservoir.

So efficiency of any heat engine is not possible to have 100%

so here correct answer will be

some useful energy is lost as heat whenever an energy transfer occurs.

Answer 2

the answer is energy is not created nor destroyed, but it can change from one energy form to another.