Principles Of Chemistry

Question 1

Characteristics of a liquid

Answer 1

• close together but randomly arranged
• move around each other
• more energy than a solid

Question 2

Characteristics of a gas

Answer 2

• very weak forces
• particles move in all directions and have more energy than a liquid
• arranged randomly

Question 3

Solid liquid
Liquidgas
Solid—->gas

Answer 3

Melting , freezing
Condensing , BOILING
sublimation

Question 4

Describe melting

Answer 4

When you heat a solid the energy makes the particles vibrate faster. Eventually they vibrate fast enough so that the forces of attraction are no longer strong enough to hold each other together

Question 5

Describe freezing

Answer 5

If a liquid is cooled down its move slower until eventually they will be held in a regular arrangement

Question 6

Describe boiling

Answer 6

When a liquid is heated strongly the particles have enough energy to break all forces of attraction

Question 7

Describe condensing

Answer 7

If you cool a gas down the particles eventually move slowly and decrease in energy enough for the attractions between them to hold them in liquid form

Question 8

What is evaporation

Answer 8

When a liquid turns to a gas at a temperature other than boiling point .particles move at different speed as they have different amount of energy

Question 9

Describe sublimation

Answer 9

When a solid turn directly into a gas eg iodine

Question 10

Define diffusion

Answer 10

The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient

Question 11

Characteristics of a solid

Answer 11

• particles close together and held by strong bonds
• vibrating in fixed position
• arranged in a regular pattern

Question 12

Two experiments for diffusion

Answer 12

1)jar of bromine - brown diffuses up
2)ammonia at one end , hcl on other
Ammonium chloride ring forms closer to hcl meaning it diffuses slower

Question 13

The speed of diffusion takes place depends on….

Answer 13

The amount of energy the particles have …. Basically temperature
The mass of the particles diffusing ….heavier particles move slower

Question 14

What are atoms made of

Answer 14

Protons , neutrons and electrons

Question 15

What is a molecule

Answer 15

a group of two or more non-metal atoms joined together by covalent bonds

Question 16

What are elements

Answer 16

Something that contains only one type of atom

Question 17

What are compounds

Answer 17

A combination of two or more elements in a fixed ratio and joined by bonds

Question 18

What are mixtures

Answer 18

Elements and compounds can also be mixed together as well as just the molecules . There is no fixed ratio or bonds so they are easy to separate

Question 19

When would you use filtering

Answer 19

To separate insoluble particles from a liquid eg sand from water

Question 20

When would you use evaporation (separation techniques)

Answer 20

To remove substances dissolved in a solution eg salt from salt water

Question 21

when would you use distillation (separation techniques)

Answer 21

When you want the liquid in a solution and not the dissolved solid …. Or the liquid from a mixture of liquids

Question 22

When would you use chromatography ?

Separation techniques

Answer 22

Separating a mixture of soluble substances

Question 23

How to interpret chromatographs

Answer 23

The substance thats the most soluble with travel the furthest

Question 24

What is fractional distillation

Answer 24

Two or more miscible (things that mix with another) liquids with different boiling points .the one with the lower boiling point evaporates faster and travels higher up then condenses in the condenser

Question 25

Describe an experiment in which we can realise how small particles are.

Answer 25

Dilution: if you dissolve 0.1 g of potassium permanganate In 10 cm³ of water you get a deep purple solution. Assume that the smallest drop you see is 1/1000 cm³. This means the whole solution is made from 10,000 drops. So each drop will contain 0.0001 g of potassium permanganate. If you continue to dilute this by a factor of 10, you will see colour up to the fifth dilution. If you assume you only need one particle of potassium permanganate to see the colour, the particle cannot wait more than 0.000000001 g.