Environmental Chemistry

Question 1

Distinguish between physical and chemical changes

Answer 1

Physical change:
- No new substance
- Can be reversed
- No energy given out or taken in
Chemical change:
- Opposite of the above named thingymagingies

Question 2

Name three types of chemical reactions, and describe each one shortly

Answer 2

1. Synthesis reaction - two or more substances join to form a new one
2. Combustion - reaction with oxygen
3. Decomposition - when a substance is broken down into two or more products

Question 3

Name five properties of acids

Answer 3

• Sour taste
• Turns litmus paper red
• pH less than 7
• Include non-metal oxides
• Contain hydrogen

Question 4

Name four properties of bases

Answer 4

• Soapy feel
• Bitter taste
• pH more than 7
• Include metal oxides & hydroxides

Question 5

Distinguish between a strong and a weak acid

Answer 5

A strong acid will dissociate completely in water, whereas a weak acid will only dissociate partially

Question 6

Describe neutralisation

Answer 6

The reaction of an acid and a base in order to neutralise the acid. Neutralisation is used to prepare salts

Question 7

Describe the preparation and test for oxygen

Answer 7

Preparation: Decomposition of hydrogen peroxide
Test: Will relight a glowing splint

Question 8

Describe the preparation and test for carbon dioxide

Answer 8

Preparation: Reacting calcium carbonate and HCl
Test: Will turn clear limewater milky

Question 9

Describe the preparation and test for hydrogen

Answer 9

Preparation: Reacting a metal and an acid
Test: Match will make popping sound

Question 10

Describe fractional distillation of air

Answer 10

Fractional distillation of air involves cooling and compressing air to -200 degrees. Solid carbon dioxide is removed as “dry ice” at -80 degrees. The air is then slowly heated and different gases are collected at different temperatures.

Question 11

Describe the industrial process used to convert nitrogen to ammonia and nitrates

Answer 11

The Haber process is used. This involves reacting nitrogen (fractional distillation) and hydrogen (natural gas) under high pressure and temperature (400-450 degrees) and cooling the ammonia. Unused nitrogen and hydrogen is recycled and the process starts over. The mixture in the main reaction tank contains about 10% ammonia. Ammonia is used to make nitric acid, which is converted to nitrate salts, and then used in fertilisers.

Question 12

Name five uses of oxygen

Answer 12

• Production of steel
• Welding
• Hospitals
• Mountain climbers
• Deep sea divers

Question 13

Name four uses of carbon dioxide

Answer 13

• Fizzy drinks
• Refrigiration
• Fire extinguishers
• Baking

Question 14

Name two uses of nitrogen

Answer 14

• Fertilisers

- Refrigirant

Question 15

Define air pollution

Answer 15

• The formation of harmful particles in the air

Question 16

Name five sources of air pollution

Answer 16

• Burning of forests
• Marine vessels burning fuels
• Oil refinering
• Coal power plants
• Road vehicle emission gases

Question 17

Name two pollutant gases originating from car exhaust systems

Answer 17

• Sulphur dioxide

- Nitrogen oxide

Question 18

Name the product of incomplete combustion, and state why it is harmful to humans

Answer 18

Carbon monoxide

Breathing in carbon monoxide can lead to unconciousness and eventually death

Question 19

Describe the formation of acid rain

Answer 19

Sulphur dioxides and nitrogen oxides produced by industrial activities and the emission systems of cars rises into the air and dissolves into water droplets, which leads to acid rain

Question 20

Name two effects of acid rain on the environment

Answer 20

• Damages limestone buildings and statues by dissolving the limestone
• Damages the waxy cuticles on leaves

Question 21

Describe the working of a catalytic converter

Answer 21

Catalytic converters prevent air pollution by converting nitrogen oxides, carbon monoxide and unburned hydrocarbons into water, carbon dioxide and nitrogen

Question 22

Name four solid particle pollutants

Answer 22

• Smoke
• Ash
• Mineral dust from soil
• Mica dust

Question 23

Name one effect of mica dust on the human body

Answer 23

Mica dust causes a lung disease called pneumoconiosis

Question 24

Describe a chemical test to determine the presence of water

Answer 24

White anhydrous copper (II) sulphate will turn blue in the presence of water, and blue cobalt (III) chloride will turn pink

Question 25

Describe a physical test for water

Answer 25

Water can be physically tested for by using the boiling point and density of water. If a substance boils at 100 degrees or if the density of the substance is 1g/cm3, the chance of it being water is very high

Question 26

Explain why ice floats on water

Answer 26

The density of ice is 0,9 g/cm3, whereas the density of water is 1 g/cm3, therefore ice will foat on water

Question 27

Describe the importance of the expansion of water between 4 and 0 degrees, referring to the survival marine animals and plants

Answer 27

Due to this unusual phenomenon, ice always forms on the surface of lakes and dams. The water at the bottom is the warmest, making it possible for marine animals and plants to survive during the winter

Question 28

Distinguish between soft and hard water

Answer 28

Soft water lathers easily, whereas hard water does not lather easily and forms scum

Question 29

Describe scum (The answer “My friends” is not acceptable)

Answer 29

The product of soap and calcuim and magnesium salts in water

Question 30

Name the substances causing temporary hard water

Answer 30

Calcium and/or magnesium hydrogen carbonate

Question 31

Name the substances which cause permanent hard water

Answer 31

Calcuim and/or magnesium carbonate

Question 32

Describe how temporary hard water can be softened, and name the substance which forms on the side of the apparatus used

Answer 32

Temporary hard water can be softened by boiling, and scale forms at the side of the kettle

Question 33

Describe how scale can be removed from the inside of a kettle

Answer 33

Scale can be removed by the reaction with a weak or dilute acid, like vinegar