# IBDP Physics 3.2 – Modelling a gas: IB Style Question Bank- HL Paper 1

### Question

Two ideal gases X and Y are at the same temperature. The mass of a particle of gas X is larger than the mass of a particle of gas Y. Which is correct about the average kinetic energy and the average speed of the particles in gases X and Y?

 Ans: Average kinetic energy Average speed A larger for Y larger for Y B same larger for Y C same same D larger for Y same

Ans: B

Average speed Hence lighter particle will have higher Average Speed.
The Kinetic energy associated with each degree of freedom has the same average value (i.e., ), and this average value depends on temperature. Hence it is independent of mass of particle.

### Question

What is not an assumption of the kinetic model of an ideal gas?

A  Attractive forces between molecules are negligible.

B Collision duration is negligible compared with time between collisions.

C Molecules suffer negligible momentum change during wall collisions.

D  Molecular volume is negligible compared with gas volume.