3.1 Introduction

Question 1

Good observations when describing substances

Answer 1

• Solid, Liquid, Gas?
• Coloured or Colourless?
• Crystalline or Powdered (Solid)?
• Clear or Cloudy (Liquid)?

Question 2

Good observations when describing change

Answer 2

• Fizzing/Effervescence?
• Solid appeared or disappeared?
• Colour change?
• Sounds or smells?

Question 3

Physical change

Answer 3

• No new substances
• Easy to reverse
• Release small amounts of energy

Question 4

Example of physical change

Answer 4

Ice melting, can be frozen again

Question 5

Chemical change

Answer 5

• Creates new substance
• Difficult to reverse
• Release large amounts of energy

Question 6

Example of chemical change

Answer 6

Burning wood, can’t reverse, very hot, turns into soot

Question 7

Chemical test for water

Answer 7

Anhydrous copper sulphate turns white to blue if water is present

Question 8

Physical tests for water

Answer 8

Melting point = 0C
Boiling point = 100C

Purer water matches properties closer

Question 9

Element

Answer 9

One type of atom

Question 10

Properties of a metal

Answer 10

• High melting/boiling point
• Electrical conductors
• Malleable
• Shiny

Question 11

Properties of a non-metal

Answer 11

• Low melting/boiling point
• Electrical insulators
• Brittle
• Dull

Question 12

Which are the diatomic elements?

Answer 12

Found in an L shape starting at nitrogen to astatine

Question 13

Compound

Answer 13

More than one type of atom, chemically bonded

Question 14

How to make a compound

Answer 14

Compounds are often formed by heat, e.g. Zinc + Sulphur —> Zinc Sulphide

Question 15

Types of compounds

Answer 15

Metallic, Ionic (metal + non-metal), Covalent (non-metals)

Question 16

Ammonium Chloride Tube Practicle

Answer 16

• Making the compound ‘Ammonium Chloride’ is used to show diffusion
• Two gases diffuse from 2 ends of sealed tube (Ammonium + Hydrogen Chloride)
• Hydrogen Chloride doesn’t diffuse as far, meaning it’s molecules are heavier
• Heating up tube increases rate of reaction as they have more energy and collide more often

Question 17

Solute

Answer 17

The substance going to be dissolved

Question 18

Solvent

Answer 18

The liquid which is going to do the dissolving

Question 19

Solution

Answer 19

The mixture of the solute dissolved in the solvent

Question 20

Saturated

Answer 20

A solution in which no more solute can be dissolved in

Question 21

Suspension

Answer 21

A solid floating in the liquid as it cannot dissolve

Question 22

Soluble

Answer 22

A substance that can be dissolved

Question 23

Insoluble

Answer 23

A substance that cannot be dissolved

Question 24

Unit for solubility

Answer 24

g per 100g of solvent

Question 25

What does the line mean in a solubility curve?

Answer 25

Line = Saturated

Shows the maximum mass of solid which can be dissolved at each temperature

Question 26

What does the below the line mean in a solubility curve?

Answer 26

Below = Soluble

Shows less than maximum mass of a solid so it will all dissolve at a specific temperature

Question 27

What does the above the line mean in a solubility curve?

Answer 27

Above = Insoluble

More than the maximum mass of solid that can be dissolved. The mass that dissolves can be found by reading off the line

Question 28

What is 36g of sodium chloride per 100g in 50g?

Answer 28

18g per 50g