First Law

Note: This section needs a very basic knowledge of calculus. To see a simplified version (without equations) go HERE

Observations

The laws of thermodynamics are based on observations of the natural world. The first law is based on two observations concerning energy:

Energy can be transferred between a system and its surroundings by only two ways: work and heat
The total energy of a system and its surroundings is always constant (The conservation of energy)

These two observations can be combined into the First Law of Thermodynamics:

The internal energy of a system is constant unless changed by doing work or by heating

Mathematically, the change in internal energy is the sum of the work and heat entering or leaving the system:

[math]\Delta U = Q + W[/math]

or

[math]dU = dQ + dW[/math]

Thermodynamics
Introduction	What is this thing called Thermodynamics??? \| Definitions \| Thermal Equilibrium and Zeroth Law \| Limitations
First Law	Work, Heat, Energy, and the First Law \| Work, Heat, Energy, and the First Law (simplied) \| Derivatives \| Derivatives Exercise \| Reversibility, Enthalpy, and Heat Capacity
Second Law	Things to Think About \| Observations and Second Law of Thermodynamics \| Alternative Approach - the Clausis Inequality \| Consequences of the Second Law \| Consequences of the Second Law (simplified) \| Carnot Principle - motivation and examples \| Equivalence of Second Law Statements*
Third Law	Third Law of Thermodynamics \| Consequences of Third Law*
Development of Thermodynamics	The Thermodynamic Network \| Network Exercise \| Equations of State (EOS) \| EOS Example, Reading Tables, and Numerical Analysis \| EOS Exercises \| Thermochemistry
* Optional Section