WASSCE Physics · Paper 1 style

Thermal physics

One sample question with the full working. 3 more in the app, with instant feedback and repair sessions for the traps below.

According to the kinetic theory, the pressure of a gas is due to

Athe weight of the gas molecules
Bthe expansion of molecules on heating
Cthe collisions of gas molecules with the walls of the container
Drepulsion between molecules

Show the answer and working

Answer: C

Change in momentum per unit time per unit area.

Trap A Treats inverse relations as direct: At constant temperature PV = constant: halving the volume DOUBLES the pressure. Charles: V/T constant with T in KELVIN.

Trap B Picks a related law, device or effect with a different job: Learn laws and devices as 'name → what it tells you' cards. Contrast neighbours: left-hand rule = motor force, right-hand rule = dynamo current, grip rule = field around a wire.

Trap D Treats inverse relations as direct: At constant temperature PV = constant: halving the volume DOUBLES the pressure. Charles: V/T constant with T in KELVIN.

Traps in Thermal physics

Treats inverse relations as direct
At constant temperature PV = constant: halving the volume DOUBLES the pressure. Charles: V/T constant with T in KELVIN.
Picks a related law, device or effect with a different job
Learn laws and devices as 'name → what it tells you' cards. Contrast neighbours: left-hand rule = motor force, right-hand rule = dynamo current, grip rule = field around a wire.
Chooses a true but irrelevant statement
Re-read the question word (why, which, what causes). A true fact that answers a different question is still wrong.
Uses everyday intuition instead of physics
Name the law that applies (Newton's first law, Archimedes' principle, kinetic theory) and reason from it. If the option only 'feels' right, test it against the law.
Reverses a relationship or direction
Write the relationship with an arrow or proportionality sign first (E ∝ f; R ∝ L; cooling a metal → R falls). Then check the option follows the same direction.
Uses Celsius temperatures in gas laws
Gas laws need absolute temperature: T(K) = θ(°C) + 273. Convert every temperature before using a ratio.

Practise Thermal physics (3 questions)Send to your class on WhatsApp