Marine Engineering Practice Exam

The energy needed to heat a substance depends on its mass, how much energy its temperature can absorb per unit mass, and how big the temperature change is. For water, the specific heat is about 1 Btu per pound per degree Fahrenheit. That means one pound of water raising its temperature by one degree Fahrenheit requires 1 Btu of energy.

Since the problem has 1 lb of water and a 1°F rise, the required energy is 1 Btu. Among the options, the Btu is the unit that matches this scenario and definition. The other units represent different scales or amounts of energy and don’t correspond to heating 1 lb of water by 1°F (for example, a joule or watt-second is about 0.001 Btu, and a calorie is a different energy increment altogether). So the energy is 1 Btu.