GCE N Level Science ( Chemistry )

1. The atmosphere and Environment

2. The Atmosphere and the Environment Composition of air Air Pollution 1. Presentation in graphs/charts Identity of air pollutants 2. Experiments which show composition of air Sources/how they are formed Effects Acid rain Equations Equations

3. Composition of air Air is a mixture of several gases, both elements and compounds. Its composition varies from time to time.

4. Representations of air composition

6. Only oxygen gas will react with copper upon heating. We know that oxygen gas only constitute 20% of the volume of air. Thus , after the heated copper reacts with oxygen gas, the volume of air will decrease by 20% ( 80% of the volume of air is left. ) Thus, the volume of air left in syringe B is  80% x 200cm3 = 160cm3 Answer: Option C

7. Air pollution Definition : the pollution caused by chemicals in the air that can harm living things or damage non-living things Example - Ozone , O3 Unburnt hydrocarbons Carbon monoxide , CO Oxides of nitrogen , NO , NO2 Sulfur dioxide , SO2

8. Carbon monoxide Properties Poisonous Colourless Odourless Source Incomplete combustion of carbon-containing fuels ; i.e. incomplete combustion of petrol in car engines Effects CO reacts with haemoglobin in blood to form carboxyhaemoglobin. As a result, it cannot transport oxygen to the rest of the body. Headaches, fatigue, breathing difficulties and even death

10. 3 Dimensional model of haemoglobin

11. Oxides of nitrogen Produced in 2 ways Due to high temperature in a car engine, the nitrogen present combines with oxygen to form nitrogen monoxide (NO) or nitric oxide, a colourless gas. N2 (g) + O2 (g)  2NO (g) NO (g ) + O2 (g)  2NO2 (g) 2. Heat energy released when lightning strikes. This causes the nitrogen and oxygen to react to form NO and NO2.

12. Sulfur dioxide Source Combustion of fossil fuel e.g. coal , crude oil and natural gas Volcano eruptions Fossil fuel contains sulfur S (s) + O2 (g)  SO2 (g)

13. Effects from sulfur dioxide and oxides of nitrogen Eye irritation Lung irritation  breathing difficulties Inflammation of lungs  bronchitis Both gasses form acid rain Acid rain destroys buildings, plants and aquatic life pH of acid rain ~ 4

14. Forming acid rain SO2 (g ) + H2O (l)  H2SO3 (aq) Sulfur dioxide sulfurous acid H2SO3 then slowly reacts with oxygen to form sulfuric acid, H2SO4

15. Forming acid rain 4 NO2 (g) + 2H2O (l) + O2 (g)  4HNO3 (aq)

16. Forming acid rain CO2 (g) + H2O (l)  H2CO3 (aq)

17. Effects of acid rain Acid reacts with metals, carbonates in marble and limestone . Recall acids chapter!!! This affects metal bridges and stone buildings Makes lakes and rivers acidic  kill fish and other aquatic life. Leaches (dissolves out) important nutrients from the soil  plants are destroyed