Topic 10

Question 1

How do fertilisers and detergents pollute our water? What is this type of pollution called?

Answer 1

They contain phosphates and nitrates, which can cause algae blooms, which prevent light reaching underwater plants, so photosynthesis decreases. Plants continue to respire, so oxygen levels decrease. This is called Eutrophication

Question 2

How does thermal pollution pollute our water?

Answer 2

Water that was used as a coolant in industry is disposed of in lakes and waterways, so the temperature of the water increases. This causes gases like oxygen to be less soluble, so oxygen levels decrease

Question 3

How do pesticides pollute our water?

Answer 3

They are designed to kill pests, and can often be poisonous to humans. They can wash in to our waterways due to rain or flooding

Question 4

Define solvent?

Answer 4

The substance that does the dissolving of the solute

Question 5

Define solute?

Answer 5

The substance that dissolves in the solvent

Question 6

Define solution?

Answer 6

A substance that is a mixture of a solute and a solvent

Question 7

Define saturated solution?

Answer 7

A solution which cannot dissolve anymore solute

Question 8

Define anhydrous?

Answer 8

A substance that does not contain any water

Question 9

Define hydrated?

Answer 9

A substance that does contain water

Question 10

As temperature increases, how is the solubility of solids affected?

Answer 10

Solubility of solids increases

Question 11

As temperature increases, how is the solubility of gases affected?

Answer 11

Solubility of gases decreases

Question 12

Define solubility?

Answer 12

Solubility is a measure of how much solute dissolves in 100g of solvent at a certain temperature

Question 13

How to calculate solubility?

Answer 13

Mass of solute
—————- X 100
Mass of solvent

Question 14

Describe an experiment to determine the solubility of a solid? (8 steps)

Answer 14

• Add 10cm3 of water to test tube
• Add solid to test tube and stir until excess is present at room temperature
• Decant the saturated solution in to a weighed evaporating basin
• Weigh basin and solution
• Evaporate until it just starts to spit
• Complete drying over water bath. Heat until constant mass
• Calculate mass of solute and solvent
• Calculate solubility

Question 15

Describe an experiment to test relationship between temperature and solid? (Constructing a solubility curve) (8 steps)

Answer 15

• Weigh 4g of solute and place in boiling tube
• Place 10cm3 of water in boiling tube
• Set boiling tube in clamp and retort stand, place thermometer and stirrer in boiling tube
• Heat in water bath until solute has dissolved
• Remove from water bath, allow to cool and then record temperature at which crystals first appear
• Add 2.5cm3 of water to boiling tube
• Repeat steps 5-8 until tube holds 20cm3 of water
• Using results construct a solubility curve

Question 16

Give 4 pollutants of our water supplies?

Answer 16

Fertilisers
Detergents
Thermal Pollution
Pesticides