Click image to open full size
Gas Laws
Boyle's, Charles's, Gay-Lussac's, and Ideal Gas Law
Related Tools
Related Labs
Gas laws describe how pressure, volume, temperature, and amount of gas are related. They help explain everyday systems such as bicycle pumps, weather balloons, car tires, and breathing. By studying these relationships, students can predict how a gas will respond when one variable changes. This makes gas laws a foundation for chemistry, physics, and engineering.
Boyle's law shows that pressure and volume are inversely related when temperature and moles stay constant. Charles's law shows that volume increases with absolute temperature when pressure and moles stay constant. The ideal gas law combines several gas relationships into one equation, PV = nRT, linking pressure, volume, temperature, and amount of gas. Although real gases can deviate under extreme conditions, the ideal gas model works well for many common problems.
Key Facts
- Boyle's law: P1V1 = P2V2 at constant T and n.
- Charles's law: V1/T1 = V2/T2 at constant P and n, with T in kelvin.
- Ideal gas law: PV = nRT.
- If volume decreases while temperature and moles stay constant, pressure increases.
- If temperature increases at constant pressure, gas volume increases.
- R = 0.0821 L·atm/(mol·K) or 8.314 J/(mol·K), depending on units.
Vocabulary
- Pressure
- Pressure is the force per unit area caused by gas particles colliding with the walls of a container.
- Volume
- Volume is the amount of space occupied by a gas.
- Absolute temperature
- Absolute temperature is temperature measured in kelvin, starting from absolute zero.
- Mole
- A mole is a unit that counts particles, with 1 mol equal to 6.022 × 10^23 particles.
- Ideal gas
- An ideal gas is a simplified model in which particles have negligible volume and no intermolecular attractions.
Common Mistakes to Avoid
- Using degrees Celsius in gas law equations, which is wrong because gas law temperature must be in kelvin for proportional relationships to work correctly.
- Forgetting which variables are held constant, which is wrong because Boyle's and Charles's laws only apply under their specific constant conditions.
- Mixing units without converting them, which is wrong because pressure, volume, and temperature units must match the gas constant and equation used.
- Assuming pressure and volume change in the same direction in Boyle's law, which is wrong because they are inversely related when temperature is constant.
Practice Questions
- 1 A gas has a volume of 4.0 L at 2.0 atm. If the pressure changes to 5.0 atm at constant temperature, what is the new volume?
- 2 A gas occupies 2.5 L at 300 K. If the temperature rises to 360 K at constant pressure, what volume will it occupy?
- 3 A sealed rigid container of gas is heated. Explain what happens to the pressure and why, using particle motion and the ideal gas law.