Ideal Gas Study Guide: NEB 11 Physics

Learning target

What mastery looks like

Check the CDC Physics Grade 11 page and secondary curriculum for Nepal scope. Use the OpenStax ideal-gas reference for institutional explanations and examples.

Mastery means selecting a relation from stated controls, using absolute variables, explaining results with collisions and identifying where the ideal model becomes unreliable. The paired Ideal Gas concept guide rebuilds theory when needed.

One equation, several views

Build the state-variable map

Seven focused sessions

Ideal Gas study sequence

Use 55-minute blocks: ten minutes retrieval, ten minutes targeted reading, thirty minutes problems and five minutes error coding. Begin later sessions with one delayed problem.

Translation routine

Make a two-state table before algebra

1. Write the gas boundary.
2. Convert units on the table.
3. Cross out fixed variables.
4. Choose the simplest surviving relation.
5. Predict the direction of the answer.
6. Solve symbolically, then substitute.

Mental fluency

Practise ratios without numbers

At fixed T and n, halving V doubles P. At fixed P and n, increasing T by 25% increases V by 25%. At fixed V and n, a 10% rise in kelvin temperature gives a 10% rise in absolute pressure.

Write the proportionality first. It reveals whether a calculator answer has the correct direction.

Graph language

Match axes to a controlled process

An isothermal P–V graph is a hyperbola, while P against 1/V is linear through the ideal origin. At constant pressure, V against T in kelvins is linear. At constant volume, P against T in kelvins is linear.

A Celsius-axis extrapolation may approach −273.15°C, but no ordinary ideal-gas experiment reaches that point; phase changes and non-ideal behaviour intervene. Label the experimentally supported range and avoid treating extrapolation as direct measurement.

Explain calculations

Use collisions and kinetic energy

The OpenStax kinetic-theory reference connects PV=(1/3)Nm⟨v²⟩ with average translational energy 3k_BT/2. Practise explaining a constant-volume pressure rise: molecules move faster on average, collide more often and transfer more momentum per collision.

At equal T, hydrogen and oxygen molecules have equal average translational kinetic energy, but hydrogen has greater rms speed. If temperature quadruples, rms speed doubles because v_rms∝√T.

Use PhET Gas Properties with a prediction table. Change only one variable and describe both the state equation and collision-level cause.

Evidence and uncertainty

Analyse a Boyle-law investigation

Plot absolute pressure against reciprocal volume for a trapped gas. Use slow volume changes to reduce warming, allow equilibrium, include connector dead volume and watch for leakage. A best-fit line is stronger than forcing every point through an expected curve.

Spaced correction

Turn the first wrong decision into a schedule

Code scale, boundary, fixed variable, equation, graph, molecular explanation, unit or algebra. Redo after one day with changed values, after three days in a mixed set and after seven days from an empty state table. Review Heat & Temperature if equilibrium and temperature language remain weak, and Physical Quantities for conversions.

Final self-test

Ideal Gas readiness checklist

• Pressure is absolute and temperature is kelvin.
• The gas boundary and fixed amount are explicit.
• Controlled-variable laws come from PV=nRT.
• Two-state tables use consistent units.
• Graphs match their fixed variables.
• Kinetic explanations mention momentum transfer.
• Model limits and experimental bias are stated.

1. Solve three gas-law ratios.
2. Find n from one state.
3. Complete a two-state problem.
4. Explain rms-speed scaling.
5. Evaluate Boyle-law data.

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References and next steps

Sources and related study guides

• CDC Nepal: Physics Grade 11
• CDC Nepal: Secondary Curriculum
• OpenStax: Ideal Gas Law
• OpenStax: Kinetic Theory
• OpenStax: Gas Concept Questions
• PhET: Gas Properties

Use the Ideal Gas Practice Set to test calculations and explanations under timed conditions. Curriculum scope and sources were checked on 2 August 2026; follow current CDC, NEB and college instructions if requirements change.

Oral transfer test

Explain four unfamiliar situations

Explain a sealed bottle warming, a flexible balloon rising, a bicycle pump heating during rapid compression and a pressure sensor with a small leak. For each, state system boundary, fixed variables, equilibrium assumption and collision-level cause. If the process is rapid, say why an isothermal assumption may fail.

Record the explanations, then replace vague phrases such as “particles expand” with changes in molecular speed, collision rate, momentum transfer or available volume.

Integrated revision challenge

Build and defend a complete solution

A sealed 5.0 L vessel contains gas at 120 kPa absolute and 300 K. It is connected to an evacuated 3.0 L rigid vessel and allowed to equilibrate at the same temperature. If the connecting system is rigid and no gas escapes, total available volume becomes 8.0 L and the ideal final pressure is 120×5/8=75 kPa. Write why total amount and temperature are fixed before applying the ratio.

Now suppose final temperature is 320 K. Use P₂=P₁V₁T₂/(T₁V₂)=80 kPa. Explain the molecular difference: greater available volume reduces wall-collision frequency per area, while the temperature rise partly offsets it by increasing average molecular kinetic energy.

Complete an error audit. If a learner used 47°C/27°C, label temperature scale. If 3.0 L was omitted, label system geometry. If the evacuated vessel was treated as containing a negative amount of gas, label state interpretation. Redo the problem after two days with new volumes and a lower final temperature.