Heat Capacity Worked Example Problem

Heat capacity is the amount of heat energy required to change the temperature of a substance. This example problem demonstrates how to calculate heat capacity. Problem: Heat Capacity of Water From Freezing to Boiling Point What is the heat in joules required to raise the temperature of 25 grams of water from 0 degrees C to 100 degrees C? What is the heat in calories? Useful information: specific heat of water 4.18 J/g ·Ã‚ °CSolution: Part I Use the formula q mcΔTwhereq   heat energym massc specific heatΔT change in temperatureq (25 g)x(4.18 J/g ·Ã‚ °C)[(100 C - 0 C)]q (25 g)x(4.18 J/g ·Ã‚ °C)x(100 C)q 10450 JPart II4.18 J 1 caloriex calories 10450 J x (1 cal/4.18 J)x calories 10450/4.18 caloriesx calories 2500 caloriesAnswer:10450 J or 2500 calories of heat energy are required to raise the temperature of 25 grams of water from 0 degrees C to 100 degrees C. Tips for Success The most common mistake people make with this calculation is using incorrect units. Make certain temperatures are in Celsius. Convert kilograms to grams.Be mindful of significant figures, particularly when working problems for homework or an exam.