Question

Which of the following has the most thermal energy?

500 mL water at 25°C

1.5 L water at 25°C

15 L water at 25°C

Answer 1

15 L of water at 25°C.

Reason: thermal energy (internal energy) for a substance at a given temperature is proportional to its mass: Q ∝ m c T (or more precisely m c ΔT from a reference). All three have the same temperature, so the one with the largest mass has the most thermal energy.

Quick check (density = 1 g/mL, c ≈ 4.18 J/g·°C, taking 0°C as reference):
- 500 mL → 500 g: Q = 500·4.18·25 ≈ 5.22×10^4 J
- 1.5 L → 1500 g: Q ≈ 1.57×10^5 J
- 15 L → 15000 g: Q ≈ 1.57×10^6 J

So 15 L has the most thermal energy.