2 Work, Heat, and Energy:
The First Law of Thermodynamics
PRINCIPAL FACTS AND IDEAS
1. Thermodynamics is based on empirical laws.
2. The first law of thermodynamics asserts that the internal energy U is a
state function if
∆U q + w
where q is an amount of heat transferred to the system and w is an amount
of work done on the system.
3. Heat is one way of transferring energy.
4. Work is another way of transferring energy.
5. The first law of thermodynamics provides the means to calculate amounts
of work and heat transferred in various processes, including adiabatic
processes.
6. The enthalpy is a state function whose change in a constant-pressure
process is equal to the amount of heat transferred to the system in the
process.
7. The enthalpy change of a chemical reaction can be calculated from the
enthalpy changes of formation of all products and reactants.
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