Introduction

Question 1

what are good observations to make when describing substances in practical work?

Answer 1

• solid, liquid, gas?
• coloured or colourless?
• crystalline or powdered? (for solids)
• clear or cloudy? (for liquids)

Question 2

good observations to make when describing changes during practical work?

Answer 2

• is there any fizzing?
• has a solid appeared or disappeared?
• has anything changed colour?
• are there any unusual sounds or smells?

Question 3

how to tell if something is a physical change?

Answer 3

• creates no new substances
• are usually easy to reverse
• absorb or release small amounts of energy

Question 4

how to tell if something is a chemical change?

Answer 4

• creates new substances
• are usually difficult to reverse
• absorb or release large amounts of energy

Question 5

what is a chemical test for water?

Answer 5

anhydrous copper(II) sulphate turns from white to blue (this tells you that water is present but NOT how pure it is)

Question 6

what are two physical tests for water?

Answer 6

• melting point = 0 degrees celcius
• boiling point - 100 degrees celcius
  (purer water matches these properties more closely)