Boyle's Law
Definition and meaning of Boyle's Law in chemistry.
Boyle's Law states that, at constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume: as volume decreases, pressure increases proportionally, and vice versa.
In more detail
Mathematically, this is expressed as PV = k (a constant) at fixed temperature and moles of gas, or equivalently P1V1 = P2V2 when comparing two states. The relationship arises because compressing a gas into a smaller volume forces its molecules to collide with the container walls more frequently, raising pressure. Boyle's Law is a special case of the ideal gas law (PV = nRT) when temperature (T) and the amount of gas (n) are held constant. It was formulated by Robert Boyle in 1662 based on experiments with trapped air columns.
Key facts
| Field | Physical Chemistry |
|---|---|
| Equation | PV = k, or P1V1 = P2V2 |
| Discovered by | Robert Boyle (1662) |
| Conditions | Constant temperature and fixed amount of gas |
A gas sample occupies 4.0 L at 2.0 atm. If it is compressed at constant temperature to 2.0 L, the new pressure is found from P1V1 = P2V2: (2.0 atm)(4.0 L) = P2(2.0 L), so P2 = 4.0 atm.
Frequently asked questions
Does Boyle's Law apply to real gases?
It's an idealization that closely approximates real gas behavior at low pressure and moderate temperature, where intermolecular attractions and molecular volume are negligible; noticeable deviations occur at high pressure or near a gas's condensation point.
How is Boyle's Law related to the ideal gas law?
It is the special case of the ideal gas law, PV = nRT, obtained by holding both temperature (T) and moles of gas (n) constant, which reduces the equation to PV = constant.