Particles of matter

Question 1

States of matter

Answer 1

Solids
Liquids
Gases

Question 2

Solids

Answer 2

• Particles are closely packed in a regular arrangement.
• Do not move around but vibrate against each other.
• Have strong forces holding them together.
• Very small spaces between them.

Question 3

Liquids

Answer 3

• Particles are loosely arranged but still quite close together.
• Particles can move quite fast and slide past each other.
• Have weaker forces holding them together.
• Take the shape of the container.
• Have small spaces between them.

Question 4

Gases

Answer 4

• No particular arrangement.
• Particles are far from each other.
• Forces are extremely weak.
• Particles can move very fast and free and can collide with each other.
• Have very big spaces between particles compared to those in solids and liquids.
• Fills the whole container.

Question 5

Diffusion

Answer 5

Diffusion is a process whereby particles in liquids and gases move (separate and spread) from a highly concentrated area to an area with a lower concentration.

The process of diffusion can occur in liquids and gases.

Question 6

Physical changes

Answer 6

Freeze/solidify: A material changes from a liquid to a solid state.

Boil: A liquid changes to a gas.

When a solid change to a gas, this is called sublimation e.g. dry ice

When a gas changes to a solid, it is called deposition

Question 7

Condensation

Answer 7

The conversion of a vapour/gas to a liquid.

Question 8

Evaporation

Answer 8

When a liquid becomes a gas without forming bubbles inside the liquid volume.

Question 9

Sublimation

Answer 9

Substance directly from the solid to the gas state.

Question 10

Boiling point

Answer 10

The temperature at which a liquid boils and turns into vapour.

Question 11

Density: Mass and volume

Answer 11

→ All matter possess mass.
→ The mass gives an indication of the amount of matter that the material consists of.
→ Mass is measured in grams (g) or kilograms (kg).
→ Some of the apparatus with which mass can be determined are a triple beam balance, a mass meter and an electronic scale.
→ The volume of liquids measured with a measuring cylinder, burette or pipette.
→ Units for volume: cubic meter (m3); cubic centimetre(cm3); cubic millimetre(mm3)

Question 12

Density: Density of substances

Answer 12

→ Density of a material is the amount of mass in a given volume of the material.
→ Some materials have low density and others have high density.
e.g. a loaf of bread has a lower density than a clay brick of the same size.
→ The individual particles making up one material may have different masses .
→ There can also be more spaces between the particles.
→ Density = mass/volume

Question 13

The density of a material will depend on

Answer 13

• The nature of the particles and the strength of the forces between the particles;
• The size and type of particles it is made of ; and
• The size of the particles between the particles.

Question 14

Density: Applications

Answer 14

• Cream that floats on milk can be removed. 2% (low fat) milk or 0%(fat free) milk is sold. The cream Is sold separately.
• Different liquid densities cause bath oil to have different layers in the container.
• In some countries in Northern America, tree trunk cut offs are thrown into rivers to float down to the saw mills.

Question 15

Expansion and contraction of materials

Answer 15

→ During heating: expansion. During cooling: contraction.
• Size of the object changes, but the number of particles do not.
• Only the spaces between particles become larger or smaller.
– During expansion the spaces between particles become larger.
– During contraction the spaces between the particles are smaller.

Question 16

Pressure

Answer 16

→ A gas exerts pressure due to the collisions of the particles with each other, and against the sides of the container.

→ By pumping more gas into a container, the number of gas particles increases. This increases the number of collisions, and therefore the pressure increases.
e.g. Heating also increases the pressure. When the particles gain more energy, they move faster, and collide with greater force.

Weak forces between particles: The particles are not held together and the particles move further apart.
Strong forces between particles: The particles are held together and move or vibrate against each other.