Skip to main content
MassachusettsChemistrySyllabus dot point

How are the pressure, volume, and temperature of a gas related to one another?

State and apply Boyle's law, Charles's law, Gay-Lussac's law, and the combined gas law to calculate changes in the pressure, volume, and temperature of a gas (MA STE supporting content, behavior of gases).

A standard-level answer on the gas laws for Massachusetts high school chemistry: Boyle's law, Charles's law, and Gay-Lussac's law as relationships between pressure, volume, and temperature, the combined gas law, and the need to use Kelvin temperature, grounded in the framework's gas content.

Generated by Claude Opus 4.813 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

Have a quick question? Jump to the Q&A page

Jump to a section
  1. What this topic is asking
  2. Boyle's law
  3. Charles's law
  4. Gay-Lussac's law
  5. The combined gas law and the Kelvin rule
  6. Try this

What this topic is asking

A Massachusetts high school chemistry course expects you to use the gas laws to relate the pressure, volume, and temperature of a gas. These laws follow directly from the kinetic molecular theory: gas particles are far apart and in fast motion, so changing one variable predictably changes the others. You should be able to state Boyle's, Charles's, and Gay-Lussac's laws, use the combined gas law, and remember to work in Kelvin.

Boyle's law

Halving the volume doubles the pressure. In particle terms, forcing the same number of particles into a smaller space makes them strike the walls more often, raising the pressure. A syringe shows this: blocking the nozzle and pushing the plunger compresses the gas and the pressure climbs.

Charles's law

Doubling the Kelvin temperature doubles the volume. Heating makes the particles move faster, so to keep the pressure constant the gas must expand to give them more room. A balloon left in the sun swells; the same balloon shrinks in a freezer.

Gay-Lussac's law

In a rigid sealed container the gas cannot expand, so heating it raises the pressure instead. This is why an aerosol can carries a warning not to heat it: the rising temperature drives up the pressure until the can may burst.

The combined gas law and the Kelvin rule

The three laws are special cases of one relationship when nothing is held constant:

P1V1T1=P2V2T2\dfrac{P_1V_1}{T_1} = \dfrac{P_2V_2}{T_2}

To use any of these, temperature must be in kelvin (K=∘C+273K = {}^{\circ}\text{C} + 273). The direct proportions only work from absolute zero, so a Celsius value would give a wrong ratio (and 0 degrees Celsius is not zero motion). Pressure and volume units only need to match on both sides, since they appear as ratios.

Try this

Q1. A gas at 50 kPa and 2.0 L is compressed to 1.0 L at constant temperature. Find the new pressure. [1]

  • Cue. Boyle's law: P2=50×2.01.0=100P_2 = \dfrac{50 \times 2.0}{1.0} = 100 kPa.

Q2. Convert 27 degrees Celsius to kelvin for use in a gas-law calculation. [1]

  • Cue. K=27+273=300K = 27 + 273 = 300 K.

Exam-style practice questions

Practice questions written in the style of MA DESE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

MA Chemistry (style)3 marksA gas occupies 4.0 L at 100 kPa. The pressure is increased to 200 kPa at constant temperature. (a) Name the law that applies. (b) Calculate the new volume. (c) Explain the result using particle motion.
Show worked answer →

A 3-point Boyle's law item.

(a) 1 point: Boyle's law (pressure and volume at constant temperature).
(b) 1 point: P1V1=P2V2P_1V_1 = P_2V_2, so V2=100×4.0200=2.0V_2 = \dfrac{100 \times 4.0}{200} = 2.0 L.
(c) 1 point: squeezing the gas into half the volume packs the particles closer, so they hit the walls twice as often, doubling the pressure. Markers reward the inverse relationship and a particle-level reason.

MA Chemistry (style)3 marksA gas has a volume of 2.0 L at 300 K. It is heated to 600 K at constant pressure. (a) Name the law. (b) Find the new volume. (c) State why temperature must be in kelvin.
Show worked answer →

A 3-point Charles's law item.

(a) 1 point: Charles's law (volume and temperature at constant pressure).
(b) 1 point: V1T1=V2T2\dfrac{V_1}{T_1} = \dfrac{V_2}{T_2}, so V2=2.0×600300=4.0V_2 = 2.0 \times \dfrac{600}{300} = 4.0 L.
(c) 1 point: the law is a direct proportion that only holds from absolute zero, so temperature must be in kelvin; using Celsius would give a wrong ratio. Markers reward the kelvin requirement.

Related dot points

Sources & how we know this