3.1.1 Introduction

Question 1

What is a physical change?

Answer 1

No new substance, usually quite easy to reverse, absorbs or releases small amounts of energy. Examples - Dissolving, Melting, Freezing.

Question 2

What is a chemical change?

Answer 2

New substance is made, usually hard to reverse, absorbs or releases large amounts of energy. Examples - Explosion, Limewater turning cloudy, Combustion.

Question 3

What is the difference between an observation and an inference?

Answer 3

An observation is just what you see with no explanation. Whereas an inference is why you think you see something.

Question 4

What is an element?

Answer 4

A substance containing 1 type of atom.

Question 5

What is a molecule?

Answer 5

A small group of atoms that have been chemically bonded together.

Question 6

What is a compound?

Answer 6

A substance containing more than 1 element that have been chemically bonded together.

Question 7

What are the state symbols?

Answer 7

S-solid
L-liquid
G-gas
Aq-aqueous (dissolved in water)

Question 8

What is the chemical test for water?

Answer 8

Anhydrous copper(II) sulphate: turns from white to blue.

Question 9

What are 2 physical tests for water

Answer 9

Melting point (MP) = 0°C
Boiling point (BP) = 100°C
Purer water matches these properties more closely.