What are the Gas Laws?
The gas laws describe how the pressure, volume, temperature, and amount of a gas relate to one another. Boyle's Law, Charles's Law, and Avogadro's Law each capture one relationship, and together they combine into the Ideal Gas Law.
The gas laws state that pressure, volume, and temperature of a gas are all connected through the amount of gas present; combined, they give the Ideal Gas Law PV = nRT.
- •Pressure and volume are inversely related
- •P₁V₁ = P₂V₂
- •Compressing a gas raises its pressure
- •Used in syringes and scuba tanks
- •Volume and temperature are directly related
- •V₁/T₁ = V₂/T₂
- •Heating a gas expands it
- •Seen in hot-air balloons
Try it: interactive calculator
Step-by-step worked examples
A gas at 2 atm occupies 5 L. It is compressed to 2 L at constant temperature using Boyle's Law. Find the new pressure.
P₁V₁ = P₂V₂ 2 × 5 = P₂ × 2 P₂ = 10/2 = 5 atm
0.50 mol of gas at 300 K occupies 12.3 L. Find its pressure using the Ideal Gas Law.
PV = nRT → P = nRT/V P = (0.50 × 0.0821 × 300) / 12.3 P = 12.315/12.3 ≈ 1.00 atm
A gas occupies 400 mL at 300 K. At constant pressure, it is heated to 600 K. Find the new volume using Charles's Law.
V₁/T₁ = V₂/T₂ 400/300 = V₂/600 V₂ = 400 × 600/300 = 800 mL
Flashcards
Quick quiz
Q1.A gas at 4 atm and 6 L is compressed to 3 L at constant temperature. What is the new pressure?
Q2.Which variable does the Ideal Gas Law add to Boyle's and Charles's Laws?
Q3.In PV = nRT, temperature must be measured in…
Q4.At constant pressure, heating a gas causes its volume to…
The full card deck, worked steps and AI-tutor support for “What are the Gas Laws?” are in Notek — study by hand before your exam.
Common mistakes
Using Celsius directly in gas law equations. — Correct: Convert to Kelvin first: K = °C + 273.
Assuming pressure and volume are directly proportional. — Correct: At constant T they are inversely proportional (Boyle's Law).
Mixing units of R with volume in mL or pressure in Pa. — Correct: Match units to R (atm, L, mol, K) or convert R accordingly.
Forgetting that the Ideal Gas Law assumes n (moles) is constant unless it's a variable in the problem. — Correct: Track n as its own variable — it can also change (e.g., adding more gas).
FAQ
What are the gas laws?
The gas laws are a set of relationships — Boyle's, Charles's, Avogadro's and the combined Ideal Gas Law — describing how pressure, volume, temperature and moles of a gas interact.
What is the gas laws formula?
The key formula is the Ideal Gas Law, PV = nRT, which combines Boyle's, Charles's and Avogadro's Laws into one equation.
What are some gas laws examples?
Compressing air in a bicycle pump (Boyle's Law), a hot-air balloon expanding when heated (Charles's Law), and inflating a tire with more air (Avogadro's Law) are everyday examples.
How do you calculate gas laws problems?
Identify which variables are constant, choose the matching law (or use PV = nRT for all four variables), keep temperature in Kelvin, and solve algebraically.