According to the material, which statement best reflects the first law of thermodynamics?

According to the material, which statement best reflects the first law of thermodynamics?

• A. Energy cannot be created or destroyed
• B. Energy can be created from nothing
• C. Temperature is a measure of energy
• D. Entropy decreases in all processes

Answer: (A)

The main idea here is that energy is conserved in thermodynamics. The first law says energy cannot be created or destroyed in an isolated system; it can only be transformed from one form to another or transferred between the system and its surroundings. In practical terms, the change in a system’s internal energy comes from heat added to the system minus the work the system does on its surroundings. So adding heat raises internal energy, while letting the system do work lowers its internal energy, and total energy is conserved when you account for both the system and surroundings. That’s why the statement about energy not being created or destroyed is the best reflection of this principle. The other statements don’t fit: claiming energy can be created from nothing violates conservation; equating temperature directly with energy is an oversimplification—the temperature relates to average kinetic energy per particle, not the total energy of the system; and saying entropy decreases in all processes contradicts the second law, which describes how entropy tends to increase (or stay the same only in ideal reversible cases).

The main idea here is that energy is conserved in thermodynamics. The first law says energy cannot be created or destroyed in an isolated system; it can only be transformed from one form to another or transferred between the system and its surroundings. In practical terms, the change in a system’s internal energy comes from heat added to the system minus the work the system does on its surroundings. So adding heat raises internal energy, while letting the system do work lowers its internal energy, and total energy is conserved when you account for both the system and surroundings.

That’s why the statement about energy not being created or destroyed is the best reflection of this principle. The other statements don’t fit: claiming energy can be created from nothing violates conservation; equating temperature directly with energy is an oversimplification—the temperature relates to average kinetic energy per particle, not the total energy of the system; and saying entropy decreases in all processes contradicts the second law, which describes how entropy tends to increase (or stay the same only in ideal reversible cases).