Heat quantity definitions – raising the temperature of water The amount of heat required to raise the temperature of 1 kg of water by 1 K (approximately 1 °C) is called:

Introduction / Context:
Historically, thermal energy was often measured in calories. Although the S.I. unit of energy is the joule, legacy thermal units still appear in engineering practice and older data sheets. This question asks you to identify the traditional name for the amount of heat that raises 1 kg of water by approximately 1 K.

Given Data / Assumptions:

• Water mass considered: 1 kg.
• Temperature rise: 1 K (or 1 °C over the relevant range).
• Standard pressure conditions assumed.

Concept / Approach:
By definition, 1 kilocalorie (kcal) is the amount of heat required to raise the temperature of 1 kilogram of water by 1 °C. In S.I. units, 1 kcal ≈ 4.1868 kJ. While modern standards use joules exclusively, the historical definition clearly labels this quantity as one kilocalorie.

Step-by-Step Solution:
Recall caloric definitions: 1 cal raises 1 g of water by 1 °C; 1 kcal raises 1 kg by 1 °C.Match the problem statement: 1 kg of water, 1 K rise → fits 1 kilocalorie.Therefore choose “kilocalorie.”

Verification / Alternative check:
Convert to S.I.: 1 kcal ≈ 4186.8 J. Using c_p,water ≈ 4.186 kJ/(kg·K), the heat for 1 kg and 1 K is Q = m * c_p * ΔT ≈ 1 kg * 4.186 kJ/(kg·K) * 1 K = 4.186 kJ, consistent with 1 kcal.

Why Other Options Are Wrong:

• Specific heat capacity of water is a property (≈ 4.186 kJ/(kg·K)), not a unit name for a fixed quantity of heat.
• Joule is the S.I. unit; the numerical amount would be ~4186.8 J, but the named historical quantity is “kilocalorie.”
• Btu and watt-hour are different energy units (1 Btu heats 1 lb of water by 1 °F; 1 Wh = 3600 J).

Common Pitfalls:
Mixing up the unit name with the material property. The question asks for the name of the amount of heat, not the value of c_p.

Final Answer:
kilocalorie