1 Kinetic Theory

Question 1

Describe the arrangement of the particles in solids.

Answer 1

In a solid, the particles are closely, and often regulary, packed.

Question 2

What is sublimation?

Answer 2

Changing state between solid and gas. A process, while a small number of particles change directly from solid to gas, without involving any liquid.

Question 3

What name is givet to each of following changes of state?

a) solid to liquid
b) gas to liquid
c) solid to gas

Answer 3

a) melting
b) condensing
c) sublimation

Question 4

What is diffusion?

Answer 4

The spreading out of particles in a gas or liquid is known as diffusion.

Question 5

What is the difference between boiling and evaportion?

Answer 5

Boiling happens if the liquid is heated very strongly (to the boiling point). The particles are moving fast enough to break all the forces of attraction in the liquid.

Evaporation happens if some particles on the surface of the liquid have enough speed to leave the liquid (happens without heating the liquid).

Question 6

What process is faster, evaporation or boiling and why is it so?

Answer 6

Boiling is faster, because all particles have enough speed to leave the liquid. (Evaporation - just some particles on surface have enough speed).

Question 7

What is the speed of an ammonia molecule in a gas?

Answer 7

About 600 m/s (2160 km/h)

Question 8

The quetion refers to the substances and their melting ponts.

Substance A (melting pont    -259 °C)
Substance B (melting pont     820 °C)
Substance C (melting pont     0 °C)

What substace has the strongest attractions between its particles an why is it so?

Answer 8

Substance B, because it has the highest melting point. Bigest amount of energy is needed to break the attractions between the particles.

Question 9

The quetion refers to the substances and their melting ponts.

Substance A (melting pont    -259 °C)
Substance B (melting pont     820 °C)
Substance C (melting pont     0 °C)

What substace is a gas, solid or can be a liquid at room temperature (20 °C)

Answer 9

Substance A - gas
Substance B - solid
Substance C - (can be) liquid

Question 10

What gas particles have the higher speed, HCl or HBr? Explain your answer.

Answer 10

The speed of HCl particles is higher, because the relative atomic mass Mr is lower.