Chemistry / Unit 4 Chem 0648 worked example, 60 to 90 seconds
Calculating Heat from Mass, Specific Heat, and Temperature Change
The idea
Calculating heat from a temperature change means multiplying a substance's mass by its specific heat and by the temperature change it undergoes.
In practice
A flask holds 8.0 × 10² g of water heated from 21 °C to 85 °C. Multiplying 8.0 × 10² g by water's specific heat, 4.184 J/g°C, and by the 64 °C change gives about 2.1 × 10⁵ J absorbed. The positive sign shows the water absorbed heat as its temperature rose, matching the direction of the measured change. This same three-factor product applies to any substance once its mass, specific heat, and temperature change are all known.
Where people slip
Using the initial temperature alone instead of the temperature change, final minus initial, produces an answer with no connection to how much the sample actually warmed.
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