C11 water and air

Question 1

Eutrophication

Answer 1

The nitrates from excessive use of fertilizers get into water. This causes the growth of algae that eventually die and decay. The bacteria responsible for this decay use up the oxygen in the water causing the amount of dissolved oxygen to decrease and kill animal life

Question 2

Aqueous solution

Answer 2

A solid dissolved in water

Question 3

Solvent

Answer 3

Liquid that dissolves solids. Water is the most common solvent and is excellent at dissolving ionic substances. Non aqueous solvents are good at dissolving molecular solids such as oil and grease

Question 4

Soluble/insoluble

Answer 4

If a solid is able to dissolve of not in a particular solvent

Question 5

Fractional distillation

Answer 5

A process by which components in a chemical mixture are separated according to their different boiling points. Vapors from a boiling solution are passed along a column. The temperature of the column gradually decreases along its length. Components with higher boiling points condense on the column and return to the solution; components with a lower boiling points pass through the column and are collected

Question 6

Rusting

Answer 6

The formation of reddish brown ferric oxides on iron by low temperature oxidation, in the presence of water and air

Question 7

Ammonia

Answer 7

Alkaline has made in the Haber process from nitrogen and hydrogen

Question 8

Ammonium salts

Answer 8

Ammonium nitrate, sulfate or chloride. Made by neutralizing ammonia with a particular acid. Very soluble and useful as a chemical fertilizer.

Question 9

Fertilizer

Answer 9

Compounds that contain vital elements requires for healthy growth of plants. These mainly include the elements nitrogen, phosphorous and potassium (NPK)

Question 10

Litmus paper

Answer 10

Used as a test for the alkaline nature of ammonia gas. Damp red litmus will turn blue

Question 11

Leaching

Answer 11

High solubility of chemical fertilizers in water means that they may be washed from the land into local streams and rivers causing massive environmental impact (eutrophication). Can be reduced by using less fertilizer and by not using before heavy rain

Question 12

Haber process

Answer 12

A reversible reaction where nitrogen and hydrogen react to give ammonia. Process is favored by high pressure and low temperatures with an iron catalyst

Question 13

Chlorination

Answer 13

The process by which chlorine is added to drinking water to kill the bacteria

Question 14

Sacrificial protection

Answer 14

By attaching a more reactive metal to iron, for example zinc, the zinc will corrode in preference to the iron. As a result the iron does not rust. Ships have zinc blocks attached to them and are periodically replaced

Question 15

Conditions required for iron to rust

Answer 15

Oxygen and water must be present. Salt also helps to speed up the rusting

Question 16

How do oil, greasing and painting prevent rust forming? What are the disadvantages to this method?

Answer 16

It forms a barrier to prevent the iron from being exposed to the air and moisture.
The barrier could be scratched/ damaged, and the rusting will start

Question 17

Galvanising

Answer 17

to coat iron or steel with a protective layer of zinc to form a zinc oxide. This prevents the zinc from corroding and the iron from rusting

Question 18

Difference between galvanising and sacrificial protection

Answer 18

Galvanising: only occurs with zinc. Must coat all of the iron
Sacrificial protection: Can be used with any metal more reactive than iron. Does not need to cover all of the iron

Question 19

The composition of clean air

Answer 19

a mixture of 78% nitrogen, 21% oxygen, and small quantities of noble gases, water vapor and carbon dioxide

Question 20

Common air pollutants

Answer 20

Carbon monoxide, sulfur dioxide, oxides of nitrogen

Question 21

Tests for water (there’s 2)

Answer 21

1) add anhydrous copper II sulphate to water. It should turn from white to blue
2) Dip in a piece of dry blue cobalt chloride paper. It should turn from blue to pink

Question 22

causes of carbon monoxide

Answer 22

Burning of fuels (300 million tonnes per year) Forest fires, biological processes (3000 million per year)

Question 23

causes of sulphur dioxide

Answer 23

burning of coal, oil, and roasting of sulphide ores (146 million a year) Volcanoes (9 million per year)

Question 24

causes of hydrocarbons

Answer 24

vehicle exhausts, chemical processes (88 million per year) Biological processes (1000 million per year)

Question 25

causes of nitrogen oxides

Answer 25

Vehicle exhausts, burning of fuels (50 million per year) Bacterial action in soils, electrical storms (160 million per year)

Question 26

causes of ammonia

Answer 26

Waste treatment (4 million per year) Biological decay (150 million per year)

Question 27

causes of hydrogen sulphide

Answer 27

Chemical processes, sewage treatment (3 million per year) Volcanoes and biological decay (65 million per year)

Question 28

Fractional distillation of liquefied air

Answer 28

1) the air is turned into a mixture of liquids. This is done by cooling air so that water can freeze and be removed
2) The remaining air is cooled to -200 degrees celsius where it is liquefied
3) Liquid air is warmed up to -185 degrees celsius in the fractionating column - causes all nitrogen to evaporate and rise up the column
4) Liquid oxygen is piped out at the bottom

Question 29

Freezing point of carbon dioxide

Answer 29

-79 degrees celsius

Question 30

Boiling point of oxygen

Answer 30

-183 degrees celsius

Question 31

Boiling point of Nitrogen

Answer 31

-196 degrees celsius

Question 32

Boiling point of argon

Answer 32

-186 degrees celsius

Question 33

How is water purified?

Answer 33

1) goes through a screen- traps any large particles such as twigs
2) a coagulant is added- a chemical to make all the small suspended particles stick together
3) air is blown through the water in flotation tanks, to make the coagulated particles float to the top and be skimmed off
4) Water passed through a bed of sand to filter it. It may go through further filters, e.g charcoal to remove bad tastes /smells
5) Chlorine added to kill bacteria. Fluorine can be added to help fight tooth decay
6) Water pumped into a storage reservoir