Required Practicals

Question 1

Disappearing Cross

Answer 1

1) Add hydrochloric acid to the flask and swirl to mix reactants
2) Start Timer
3) When cross is no longer visible stop the timer
4) Repeat experiment using hydrochloric acid of a different concentration

Question 2

Chromatography

Answer 2

1) Draw a ‘start line’ in pencil on a piece of absorbent paper

2) Put samples of five known food colourings and the unknown substance on ‘start line’

3) Dip paper into a solvent

4) Wait for solvent to travel to top of the paper

5) Identify substance X by comparing the horizontal spots with the results of food colourings

Question 3

Purifying water - distillation

Answer 3

1) heat water using Bunsen burner

2) This will form water vapour which travels along a tube

3) water condenses as it enters the cold test tube which turns back into a liquid

Question 4

Waste water Treatment

Answer 4

1) Sewage is screened by passing thru a mesh

2) sewage settles in sedimentation tanks producing effluent + sludge

3) sludge digested by anaerobic bacteria in absence of o2 can produce bio gas burned for electricity

4) digested sludge used as fertiliser for farming

5) Air is bubbled through liquid effluent allowing aerobic bacteria to multiply

6) in presence of 02 aerobic bacteria digest organic molecules + harmful microorganism

7) liquid effluent safely discharged into sea