In calorimetry, the expression q = m c ΔT calculates the energy change for which component?

• A. The energy released by the reaction.
• B. The final temperature of the water.
• C. The energy absorbed by the water.
• D. The mass of the water.

Answer: (C)

The expression q = m c ΔT tells you how much energy is transferred as heat when a substance changes temperature. In a calorimetry setup, the water is the substance whose temperature changes, so q represents the energy the water has absorbed (positive if it warms). If the reaction releases heat, that energy goes into the water, making its q positive and equal in magnitude to the heat released by the reaction but with opposite sign when you compare the two systems. The final temperature or the mass themselves aren’t the energy—they’re inputs or properties used to calculate the heat. The key idea is that q = m c ΔT quantifies the energy gained by the water in the process.