10.3 Air quality and climate Flashcards
The composition of clean air
78% nitrogen, 21% oxygen, 0.96% noble gas, 0.04% carbon dioxide.
Aqueous
A substance (solute) dissolved in water.
Testing for presence of water
We can use two substances to test for the presence of water
Cobalt(II) chloride paper is blue when dry (anhydrous). However, if it is exposed to water, cobalt(II) chloride paper changes from blue to pink
Copper(II) sulfate is white when it is in an anhydrous state. When exposed to water, the copper(II) sulfate changes from white to blue.
Testing for impurities of water
To test for purity, you can instead use a physical test. A physical test is done by investigating a liquid’s freezing and boiling points, which are also called its fixed points.
Pure substances, like pure water, have exact fixed points:
water freezes at exactly 0 oC
water boils at exactly 100 oC (at normal air pressure).
Melting range
If when testing for impurity of a substance and the point at which it melts is spread out this is a melting range
water from natural sources may contain substances, including:
(a) dissolved oxygen
(b) metal compounds
(c) plastics
(d) sewage
(e) harmful microbes
(f) nitrates from fertilisers
(g) phosphates from fertilisers and detergents
Substances in water which are beneficial, including:
(a) dissolved oxygen for aquatic life
(b) some metal compounds provide essential minerals for life
Substances in water which are potentially harmful, including:
(a) some metal compounds are toxic
(b) some plastics harm aquatic life
(c) sewage contains harmful microbes which cause disease
(d) nitrates and phosphates lead to deoxygenation of water and damage to aquatic life
Fertilisers
Ammonium salts and nitrates are used as fertilisers
The use of NPK fertilisers
To provide the elements nitrogen, phosphorus and potassium for improved plant growth
The source of each of these air pollutants: carbon dioxide, carbon monoxide, methane, oxides, sulfur dioxide
carbon dioxide from the complete combustion of carbon-containing fuels
carbon monoxide and particulates (smoke) from the incomplete combustion of carbon-containing fuels
methane from the decomposition of vegetation and waste gases from digestion in animals
oxides of nitrogen from car engines
sulfur dioxide from the combustion of fossil fuels which contain sulfur compounds
The adverse effects of these air pollutants: carbon dioxide, carbon monoxide, methane, oxides, sulfur dioxide
(a) carbon dioxide: higher levels of carbon dioxide leading to increased global warming, which leads to climate change
(b) carbon monoxide: toxic gas
(c) particulates: increased risk of respiratory problems and cancer
(d) methane: higher levels of methane leading to increased global warming, which leads to climate change
(e) oxides of nitrogen: acid rain, photochemical smog and respiratory problems
(f) sulfur dioxide: acid rain
Strategies to reduce the effects of these environmental issues
(a) climate change: planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy, e.g. wind, solar
(b) acid rain: use of catalytic converters in vehicles, reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurisation with calcium oxide
(c) Explain how oxides of nitrogen form in car engines and describe their removal by catalytic converters, e.g. 2CO + 2NO → 2CO2 + N2
Photosynthesis
The reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
Carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2”
Describe how the greenhouse gases carbon dioxide and methane cause global warming
(a) the absorption, reflection and emission of thermal energy
(b) reducing thermal energy loss to space
