Heat vs. Temperature
- Heat and temperature are not the same thing.
- Heat energy is the total kinetic energy of the atoms of a
substance.
- Temperature is the average kinetic energy of the atoms of
a substance.
- Each atom has a certain amount of kinetic energy. This energy fluctuates
due to the many collisions with other atoms. However, when two atoms collide
transferring kinetic energy from one to the other, no kinetic energy is lost.
If the amount of kinetic energy for each atom is added up then you would have
a value representing the heat energy of that collection of atoms. It follows
that the more atoms which are counted, the greater the heat energy will be.
- Temperature is a measure of the average kinetic energy of those atoms. The
result of this difference between heat and temperature causes the number of
atoms measured to play a major role in understanding how much heat energy
an object has at a particular temperature.
- For example, if two glasses of water are left out on the table, one completely
full and the other exactly half full, they will eventually both come to room
temperature, about 21°C. They may have the same temperature, but the full
glass has twice the heat energy of the half full glass. Because the full glass
has twice as many molecules each carrying some heat energy (or kinetic energy)
the full glass has more heat at the same temperature.
- The higher the temperature the faster the atoms move.
- Large objects can have a kinetic energy and temperature which are distinctly
separate things. For example, a baseball sitting still has no kinetic energy,
but its atoms are moving, so they have kinetic energy. Because the
temperature of a substance is due to the average kinetic energy of its atoms,
the ball does have a temperature. Depending on how many atoms it takes to
make up the ball, it has a certain amount of heat energy (the total energy
of the atoms comprising the ball).
- Because temperature is a function of the average kinetic energy of the atoms,
the lowest possible temperature would be when the atoms stop moving, therefore
having no kinetic energy. Because there is a lowest possible temperature,
it would make sense to use a temperature scale that starts at zero. This temperature
scale is called the Kelvin temperature scale and zero Kelvin is a special
temperature called absolute zero (when all atomic motion is stopped).
- An atom, however, can't separate kinetic energy from heat energy. For atoms
they are one and the same thing. A bunch of atoms sitting still have no kinetic
energy, no heat energy, and would have zero temperature (on the Kelvin temperature
scale).
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In summary:
- For an atom Kinetic Energy = Heat Energy
- For a substance Heat Energy = Total of all
the Kinetic Energies of its atoms
- For a substance Temperature = Average Kinetic
energy of its atoms