Gas Laws: Boyle's, Charles's, and Pressure Law

Gases behave in predictable, quantifiable ways when you change their pressure, volume, or temperature. The three classical gas laws — Boyle's law, Charles's law, and the pressure law — describe these relationships. Together, they form the experimental foundation for the ideal gas equation.

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Boyle's Law (Pressure and Volume)

Boyle's law states that for a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume:

pV = constant (at constant T)

Equivalently: p₁V₁ = p₂V₂

If you compress a gas into a smaller volume (without changing the temperature), the pressure increases. This makes sense from a molecular perspective: the same number of molecules occupy a smaller space, so they hit the walls of the container more frequently, creating more pressure.

A graph of p against V gives a curve (a rectangular hyperbola). A graph of p against 1/V gives a straight line through the origin, confirming the inverse proportionality.

Experimental Verification

Boyle's law can be verified using a sealed gas syringe or a Boyle's law apparatus (a column of gas trapped by oil in a glass tube connected to a pressure gauge):