Ideal Gases & Thermal Properties is one of 9 topics in the Grade 11 Physical Sciences CAPS syllabus, covered across 3 lessons on Study Vault. Below are real practice questions from this topic with full worked answers.
Sample practice questions
Easy
1. According to kinetic theory, gas molecules are in a state of:
Constant, random motion, moving at a range of different speeds
Complete rest, with no motion at all
Motion only in one fixed direction
Motion only when the gas is heated above room temperature
Answer: Constant, random motion, moving at a range of different speeds — Kinetic theory describes gas molecules as being in constant, random motion, with individual molecules moving at a wide range of different speeds at any given moment.
Easy
2. The pressure exerted by a gas on the walls of its container arises from:
The collisions of gas molecules with the container walls
The weight of the gas pressing down
The colour of the gas
Chemical reactions between gas molecules and the container
Answer: The collisions of gas molecules with the container walls — Gas pressure results from the cumulative force of the enormous number of molecular collisions with the container walls each second.
Medium
3. Which of the following is an assumption of the ideal gas model?
Gas molecules have negligible volume compared to the container, and experience no intermolecular forces
Gas molecules have significant volume and strong intermolecular attractions
All gas molecules move at exactly the same speed at all times
Collisions between gas molecules always lose kinetic energy
Answer: Gas molecules have negligible volume compared to the container, and experience no intermolecular forces — The ideal gas model assumes molecules have negligible volume, no intermolecular forces (except during collision), and perfectly elastic collisions.
