WATER

Question 1

i) Name three sources of natural water and two cations which cause hardness in water.

Answer 1

Sources of natural water:
• Sea
• Rivers
• Ponds

Cations causing hardness:
• Calcium ion
• Magnesium ion

Question 2

i) Differentiate between soft water and hard water.
ii) Give two disadvantages of hard water.

Answer 2

i) Soft water lathers easily with soap; hard water does not.
ii)
• Wastes soap
• Forms scales in kettles and pipes

Question 3

Give four economic activities associated with water.

Answer 3

Economic activities:
• Irrigation
• Electricity generation
• Washing
• Cooling machines

Question 4

Name three types of dissolved substances in water.

Answer 4

• Gases (e.g., carbon dioxide)
• Acids or alkalis
• Dissolved salts

Question 5

State two disadvantages of soft water.

ii) Name two ions found in hard water.

Answer 5

• Can cause lead poisoning from lead pipes
• Lacks calcium for strong bones

ii)
• Calcium ion (Ca²⁺)
• Magnesium ion (Mg²⁺)

Question 6

What is temporary hardness of water?

Answer 6

Temporary hardness is hardness that can be removed by boiling the water.

Question 7

i) Name three substances in rainwater.
ii) State three methods of softening hard water.

Answer 7

i)
• Oxygen
• Dust
• Carbon dioxide

ii)
• Boiling
• Distillation
• Adding washing soda

Question 8

i) Why is it important to treat water?
ii) List five methods of improving domestic water quality.

Answer 8

i) To make it safe for domestic use
ii)
• Filtration
• Boiling
• Chlorination
• Distillation
• Addition of alum

Question 9

What is hard water?

ii) What causes hardness of water?

Answer 9

i) Hard water does not lather easily with soap.

ii)
• Calcium salts
• Magnesium salts
• Iron salts

Question 10

i) Why should water be softened before use in laundries?
ii) Describe one method to remove permanent hardness.

Answer 10

i) To prevent wastage of soap and avoid fabric damage
ii) Add washing soda to remove calcium and magnesium ions

Question 11

i) Why water is a polar substance:

Answer 11

• Electrons are pulled toward oxygen
• Oxygen becomes slightly negative, hydrogen slightly positive
• Charge is unevenly distributed

Question 12

Three sources of water contamination:

Answer 12

• Domestic waste or detergents
• Industrial waste or chemicals
• Agricultural waste (fertilizers/pesticides)

Question 13

Three water purification processes:

Answer 13

• Screening
• Sedimentation
• Chlorination

Question 14

Four ways water can be contaminated:

Answer 14

• Oil spills
• Sewage/domestic waste discharge
• Industrial or mining waste
• Excess fertilizers or pesticides

Question 15

Five ways to conserve water at home:

Answer 15

• Turn off tap when brushing
• Fix leaking pipes
• Reuse water for flushing or plants
• Don’t wash cars with treated water
• Flush only when needed