Specific Heat Capacity & Temperature

In summary, the specific heat capacity of a material depends on how it divides energy between kinetic energy of molecules and other forms of energy when energy is put into the material. This is because different substances may store energy in forms other than molecular kinetic energy, such as rotational or internal modes.
  • #1
Christopher M
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This is not a homework question, just a question about physics that seems too basic to post in the main physics discussion forum. Please let me know if it is misplaced.

Temperature is average molecular kinetic energy. Is it therefore correct to say that a material's specific heat capacity depends entirely on the following question: when you put energy into the material, how does it divide that energy up between, on the one hand, kinetic energy of molecules, and on the other hand, other forms of energy?

In other words, is the reason that different substances have different specific heat capacities simply that some substances, when they take in energy, store it in forms other than molecular kinetic energy?

Thanks.
 
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  • #2
Welcome to PF!

Christopher M said:
Temperature is average molecular kinetic energy. Is it therefore correct to say that a material's specific heat capacity depends entirely on the following question: when you put energy into the material, how does it divide that energy up between, on the one hand, kinetic energy of molecules, and on the other hand, other forms of energy?

In other words, is the reason that different substances have different specific heat capacities simply that some substances, when they take in energy, store it in forms other than molecular kinetic energy?

Hi Christopher! Welcome to PF! :smile:

If we're talking about a solid, I've always assumed that the different specific heat capacities are because the molecules vibrate back and forth differently because they're more or less strongly bound.

I don't see what other forms (than kinetic energy) the energy could go into. :confused:
 
  • #3


Thanks for the response!

But if energy goes into making the molecules vibrate back and forth more energetically, doesn't that increase temperature (since temperature is average kinetic energy)?

In other words, if all the energy goes into kinetic energy -- and temperature is average kinetic energy -- how could the same amount of energy cause the temperature of different materials to rise by different amounts?
 
  • #4
Christopher M said:
Thanks for the response!

But if energy goes into making the molecules vibrate back and forth more energetically, doesn't that increase temperature (since temperature is average kinetic energy)?

In other words, if all the energy goes into kinetic energy -- and temperature is average kinetic energy -- how could the same amount of energy cause the temperature of different materials to rise by different amounts?

Hi Christopher! :smile:

Because only the translational vibrations determine the temperature (vie the Boltzmann equation), but a lot of the energy goes into rotational and other internal modes. For more detail, see wikipedia:

http://en.wikipedia.org/wiki/Thermo...ernal_motions_of_molecules_and_specific_heat" :smile:
 
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FAQ: Specific Heat Capacity & Temperature

1. What is specific heat capacity and how is it related to temperature?

Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by one degree Celsius. It is related to temperature because the specific heat capacity of a substance is dependent on its temperature. As temperature increases, so does the specific heat capacity.

2. How is specific heat capacity measured?

Specific heat capacity is typically measured using a device called a calorimeter. This device measures the amount of heat energy released or absorbed by a substance as its temperature changes. The specific heat capacity can then be calculated by dividing the heat energy by the change in temperature.

3. What are some factors that can affect the specific heat capacity of a substance?

Some factors that can affect the specific heat capacity of a substance include its chemical composition, temperature, and phase (solid, liquid, or gas). The specific heat capacity can also be influenced by external factors such as pressure, density, and the presence of impurities.

4. How does specific heat capacity impact the heat transfer process?

The specific heat capacity of a substance plays a crucial role in the heat transfer process. It determines how much heat energy is required to raise the temperature of a substance and how quickly it can absorb or release heat. Materials with high specific heat capacities are able to store more heat energy, while those with low specific heat capacities can quickly change temperature.

5. How does the specific heat capacity of water compare to other substances?

Water has a relatively high specific heat capacity compared to most other substances. This means that it requires more heat energy to raise its temperature compared to other materials. This is why water is often used as a cooling agent, as it can absorb a significant amount of heat without a large change in temperature.

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