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This question is directly linked to the definition of calorie and the specific heat of water. Option A (0.5 calorie) is incorrect — 0.5 cal/g/°C is the specific heat of ice, not water. Ice requires only half the heat that liquid water requires to achieve the same temperature rise per gram. Option B (1 calorie) is CORRECT — by definition, 1 calorie is the amount of heat required to raise the temperature of 1 gram of water by 1°C (specifically from 14.5°C to 15.5°C at standard pressure). This means the specific heat of water is 1 cal/g/°C, which is the highest specific heat among common substances. This high specific heat makes water an excellent coolant for engines and a moderating agent for climate near oceans and seas. Option C (4 calories) is incorrect — 4 calories is approximately equal to 4 × 4.186 ≈ 16.7 joules. While 1 calorie ≈ 4.186 joules, the amount needed to heat 1g of water by 1°C is 1 calorie, not 4 calories. Option D (10 calories) is incorrect — 10 calories would raise 1 gram of water by 10°C, not 1°C. Using Q = mcθ: Q = 1 × 1 × 1 = 1 calorie. For exams: specific heat of water = 1 cal/g/°C = 4186 J/kg/K (extremely important value).
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Heat is a form of energy that transfers between objects or systems due to a temperature difference, moving from a hotter body to a cooler one until thermal equilibrium is reached.
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