Slide 1
Temperature describes a state; heat is energy in transfer
Temperature describes a thermal state. Heat is energy transferred because of a temperature difference, rather than a substance stored inside an object.
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A bathtub of warm water can transfer more energy while cooling than a tiny drop of hotter water. Both the amount of material and its thermal properties matter, not just the initial thermometer reading.
Slide 2
Specific heat capacity compares energy per mass and temperature rise
Different materials need different amounts of energy for the same temperature rise. Specific heat capacity expresses this difference per unit mass.
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Water’s relatively high heat capacity helps large bodies of water moderate nearby temperatures. Land surfaces often warm and cool more quickly, contributing to daily contrasts between coastal land and water.
Slide 3
More mass needs more energy for the same warming
Twice as much of the same material needs roughly twice the energy for the same temperature rise, under otherwise comparable conditions.
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The simple relation uses mass, specific heat capacity and temperature change. It applies over ranges where heat capacity is approximately constant and no phase change consumes a substantial part of the supplied energy.
Slide 4
Melting or boiling can absorb energy without warming
During melting or boiling at fixed pressure, energy can change the phase without raising the temperature of a pure substance.
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The energy changes intermolecular arrangements rather than simply increasing thermal motion. A mixture of ice and liquid water can therefore absorb energy while remaining near its melting temperature until the ice is gone.
Slide 5
Thermal contact can bring objects to a common temperature
When objects exchange energy thermally, net heat transfer normally runs from hotter to colder. Eventually they can reach a common temperature.
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Equal final temperatures do not imply equal internal energies. Material, mass and molecular structure still differ; thermal equilibrium only removes the temperature difference that drives net transfer between them.
Sources
- The Transfer of Heat Energy
NOAA
- Air temperature over land and water
NOAA
- Heat Transfer, Specific Heat, and Calorimetry
OpenStax, Rice University
- Phase Changes
OpenStax, Rice University