Physics

Physics

Problem

Equal masses of liquid water and liquid ethanol are each heated by 10 ∘C10\,^{\circ}\text{C}. Specific heat capacities are cwater=4.18 J g−1 ∘C−1c_{\text{water}} = 4.18\,\text{J g}^{-1}\,^{\circ}\text{C}^{-1} and cethanol=2.44 J g−1 ∘C−1c_{\text{ethanol}} = 2.44\,\text{J g}^{-1}\,^{\circ}\text{C}^{-1}. Which statement is true about the magnitude of the heat qq absorbed by each liquid? a) Both liquids absorb the same quantity of heat because their temperature increases are identical. b) Ethanol absorbs more heat than water because its lower specific heat means it must take in more energy to reach the same ΔT\Delta T.},{ c) Water absorbs more heat than ethanol because its specific heat capacity is higher. d) Water absorbs less heat than ethanol because, for equal volumes, ethanol has a smaller density and therefore a smaller mass.
Intuitive explanation

The key concept here is specific heat capacity—how much energy is needed to raise the temperature of a unit mass by one degree. Since both liquids have equal mass and experience the same temperature change, the one with the larger specific heat capacity will absorb more heat. Water's cc is nearly twice that of ethanol, so water will require significantly more energy for the same warming. Think of specific heat as a material's "thermal inertia": substances that resist temperature change need more heat input.

Intuitive explanation

The key concept here is specific heat capacity—how much energy is needed to raise the temperature of a unit mass by one degree. Since both liquids have equal mass and experience the same temperature change, the one with the larger specific heat capacity will absorb more heat. Water's cc is nearly twice that of ethanol, so water will require significantly more energy for the same warming. Think of specific heat as a material's "thermal inertia": substances that resist temperature change need more heat input.

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