During a chemical reaction, how can energy change within the system?

• A. Energy is converted entirely into mass.
• B. Energy can only be released, never absorbed.
• C. Energy can be absorbed or released as heat.
• D. Energy always remains constant and does not change.

Answer: (C)

Verified step by step guidance

1. Understand that in a chemical reaction, energy changes occur due to the making and breaking of chemical bonds within the system.
2. Recall the First Law of Thermodynamics, which states that energy cannot be created or destroyed, only transformed from one form to another.
3. Recognize that energy changes in a chemical reaction typically involve absorption or release of energy, often in the form of heat (endothermic or exothermic processes).
4. Eliminate incorrect options: energy is not converted entirely into mass, energy can be both absorbed and released (not only released), and total energy is conserved but can change form within the system.
5. Conclude that the correct understanding is that energy can be absorbed or released as heat during a chemical reaction.