3: Changes of the states of matter

Question 1

What happens to the particles of a substance when it is heated?

Answer 1

When a solid/liquid is heated, the particles gain energy and vibrate faster and faster until they have
enough energy to break away from their fixed positions (break free from the forces of attraction) between
the particles and molecules.

Question 2

What happens to the particles of a substance when it is cooled?

Answer 2

When a gas/liquid is cooled, the particles lose energy and move and vibrate more and more slowly. The
particles and molecules cannot overcome the forces of attraction and move very close together (liquid) or
get stuck in a fixed position (solid).

Question 3

Define vaporisation

Answer 3

Change of state from liquid to gas

Question 4

What are the 2 types of vaporisation? Name and explain each.

Answer 4

Boiling: Occurs throughout the liquid but only at the boiling point
Evaporation: Takes place only at the surface of the liquid but at any temperature

Question 5

Define condensation

Answer 5

Change of state from gas to liquid and happens when a gas is cooled to its boiling point and below.

Question 6

Define melting

Answer 6

Change of state from solid to liquid, which is called the melting point.

Question 7

Define freezing

Answer 7

Change of state from liquid to solid, which is called the freezing point.

Question 8

Define sublimation and give an example

Answer 8

Change of state from solid directly into a gas

E.g. Dry ice (Solid carbon dioxide)/Solid Iodine

Question 9

Define deposition and give an example

Answer 9

Change of state from gas directly into a solid

E.g. Frost

Question 10

How can one test if a substance is pure/not pure?

Answer 10

Every substance has its own melting, boiling and freezing point.
One can test if a substance melts over a range of temperatures, it is not pure and is a mixture of
substances.
If it has a specific melting point, then the substance is pure.

Question 11

Define brownian motion

Answer 11

Brownian motion: Random motion of particles suspended in a fluid (liquid/gas) resulting from their collision
with fast-moving atoms in the gas/liquid.

Question 12

Define diffusion

Answer 12

Diffusion: Movement and mixing of particles, from a high concentration to a lower concentration.
The more energy particles have, the faster they can diffuse.