Chemistry / Chem 0651 · Procedure · 60–90 seconds
Solving for an Unknown Specific Heat
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Solving for an unknown substance's specific heat means dividing the total measured heat by the product of the sample's mass and its measured temperature change, rearranging the same heat equation used to compute heat from a known specific heat.
A 348-g piece of unknown metal absorbs 6.64 kJ of heat as its temperature rises from 22.4 °C to 43.6 °C. Converting 6.64 kJ to 6640 J, then dividing by the product of 348 g and the 21.2 °C temperature change, gives a specific heat near 0.90 J/g°C. Comparing that computed value against a reference table of specific heats identifies aluminum as the closest match, offering a clue to the metal's identity without directly analyzing its composition.
Forgetting to convert kilojoules to joules before dividing by the sample's mass in grams shifts the computed specific heat by a full factor of a thousand, pointing to entirely the wrong substance.