WJEC GCSE The ever-changing Earth

Starter………. Can you name the products of combustion Starter……….. Can you name the products of combustion? Write a word and symbol equation for this reaction

Lesson Objectives: LO 1: Explain the environmental effects and consequences of SO2 in the atmosphere. LO 2: Evaluate the measures used to address the problems of acid rain (sulphur scrubbing – higher tier only)

Look at the following demonstration…………….

Burning Fossil fuels CH4 (g) + 2 O2 (g)  CO2 (g) + 2H2O(l) Crude oil can be refined to give us hydrocarbon fuels such as natural gas (methane, CH4) and petrol (Octane, C8H18). When hydrocarbon fuels are burnt (combustion) in enough oxygen we produce carbon dioxide and water. CH4 (g) + 2 O2 (g)  CO2 (g) + 2H2O(l) If there is insufficient oxygen present combustion is incomplete – CO2 is not produced!. CH4 (g) + 1 1/2 O2 (g)  CO (g) + 2H2O(l) Carbon monoxide, CO, is a poisonous gas and replaces O2 in your red blood cells causing death by asphyxiation (Oxygen deficiency). If even less oxygen is present the incomplete combustion forms the solid pollutant, Carbon, more commonly known as Soot. Soot is a carbon particulate, which can cause asthma and cancer. CH4 (g) + O2 (g)  C (s) + 2H2O(l)

Fuels may contain impurities such as Sulphur. When burnt during combustion the Sulphur can react with oxygen to form SO2 (Sulphur dioxide) S (g) + O2 (g)  SO2 (g) Combustion of fuels produces a lot of heat, this allows Nitrogen and Oxygen in the air to react with each other to produce: Nitrogen Oxides (NO, NO2, N2O4). These are known as NOx. N2 (g) + O2 (g)  2NO (g)

It is not just CO2 that can dissolve into atmospheric water! Sulphur dioxide (SO2) and NOx are the major contributors to the formation of “Acid rain”. Rain is naturally acidic (pH 5.6). This is due to the rain water dissolving some atmospheric carbon dioxide. This produces a dilute solution of Carbonic acid (H2CO3) a weak acid. H2O(g) + CO2 (g)  H2CO3 (g) It is not just CO2 that can dissolve into atmospheric water!

SO2 produced from the combustion of fuel impurities can also be dissolved: SO2 (g) + H2O (g)  H2SO3 (g) This produces Sulphurous acid, H2SO3 a weak acid. H2SO3 can react further with atmospheric oxygen to form the strong acid, Sulphuric acid, H2SO4 H2SO3 (g) + 1/2 O2 (g)  H2SO4 (g) NO, produced by a ‘spark’ and high temperatures when fuel is ignited can also be dissolved: NO (g) + H2O (g)  HNO3 (g) This produces Nitric acid, HNO3 a strong acid.

Sulphurous acid (H2SO3), Sulphuric acid (H2SO4) and Nitric acid (HNO3) cause the pH of the precipitation to be more acidic. Acids are toxic to living organisms. They can inhibit the functions of enzymes and denature proteins. Effects of acid rain

QWC- Question Fossil fuels such as coal release sulfur dioxide into the atmosphere when burned. This causes acid rain. Describe how acid rain is formed and its effects on the environment. [6 QWC] Task: You must describe how acid rain is made and the effects it has on the environment using the storyboard in your own words.

Causes ? Effects? Power stations Coal Electricity Sulfuric acid Cars lorries Fuel Nitric acid atmosphere Lakes Acidic Lowers pH No oxygen Dead fish Dead trees Buildings Limestone corrode

Removing Sulphur dioxide In industry, one of the processes which we can use is known as “sulfur scrubbing” Waste gases (flue gas) is pumped through a “scrubber” before the gas is released to the atmosphere. Gas passed over solid CaO or CaCO3. This reacts with SO2 to produce gypsum (CaSO4) which is used in plasterboards.