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The internal energy E of a system has 2 components: kinetic energy and potential energy.

[itex]\Delta[/itex]E = q + w

where w is work and q is heat. heat is the transfer of thermal energy

at constant pressures, q becomes H (enthalpy)

My book says that another way to calculate the internal energy change of a gaseous reaction is to assume ideal gas behavior and constant temperature. since PV = nRT

In which case the equation would be:

[itex]\Delta[/itex]E = [itex]\Delta[/itex]H - [itex]\Delta[/itex](PV)

[itex]\Delta[/itex]E = [itex]\Delta[/itex]H - [itex]\Delta[/itex](nRT)

[itex]\Delta[/itex]E = [itex]\Delta[/itex]H - RT[itex]\Delta[/itex]n

My question is:

I know that heat is the transfer of thermal energy, and that it is a part of the total internal energy. And thermal energy depends on the kinetic energy of the molecules. But how does temperature relate to all this?

How can you have a change in heat (enthalpy) and no change in temperature?

(as the above equation shows)

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# Temperature, heat, and energy

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