A heat energy of raising 2 kg of water by 10°C using c ≈ 4184 J/kgK; what is Q?

• A. 41,840 J
• B. 83,680 J
• C. 836,800 J
• D. 8,368 J

Answer: (B)

The key idea is using the heat formula Q = m c ΔT. Here, the mass m is 2 kg, the specific heat c for water is about 4184 J/(kg·K), and the temperature change ΔT is 10 K. Multiply these together: 2 × 4184 × 10 = 83,680 J. So the heat energy required is 83,680 joules (about 83.7 kJ).

The other numbers come from using different values for mass or temperature change. For example, halving the result would happen if the mass were 1 kg or the temperature rise were 5 K, while a much larger or smaller result would come from larger or smaller ΔT or m than given. With the given values, 83,680 J is the correct calculation.