So what’s in air? Oxygen. Nitrogen. Carbon dioxide. Water vapour Argon. Other gases. But how much of each?

The ones you need to know: Nitrogen 78%, Oxygen 21% and Argon 1%.

How good is this particle diagram? Air is a mixture of different gases consisting of small molecules with large spaces between them. What about the amount of each type of gas?

Evolution of Earth’s atmosphere. Discover 1. Name the 4 gases that made up Earth’s early atmosphere? 2. Where did these gases come from? 3. Why did the oceans form? 4. Where did the first living things form? 5. What gas did they produce? 6. What is this process called? 7. How was carbon dioxide removed from the atmosphere? 8. Why was the formation of ozone important? 9. How was ammonia converted into nitrogen? 10. How long as our present atmosphere existed?

Evolution of Earth’s atmosphere. 1. Carbon dioxide, ammonia, steam and methane. 2. From the Earth’s crust (volcanoes). 3. Earth cooled down and steam condensed. 4. In the ocean. 5. Oxygen. 6. Photosynthesis. 7. Photosynthesis which then formed fossil fuels and by dissolving in the oceans and then forming sedimentary rocks. 8. It stops harmful rays form the Sun reaching the surface. 9. Reacted with oxygen and bacteria in the soil. 10. 200 million years. The answers in bold you definitely need to know!

Evolution of the Earth’s Atmosphere Carbon dioxide Methane Ammonia Oxygen Nitrogen Others Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day

Evolution of the Earth’s Atmosphere Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans. Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life. 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released. Nitrogen is also produced as a result of denitrifying bacteria on nitrates from decaying plants.

What happens to the carbon dioxide? 1. Plants use it during photosynthesis. Millions of years.

What happens to the carbon dioxide? 2. Dissolved in rain water and the sea.

What do you know about oxygen?

Element, mixture or compound? Oxygen can be obtained from the atmosphere by separating it from the other gases.

Oxygen Production Plants

Getting oxygen from the atmosphere. Air is filtered to remove dust, and then cooled in stages until it reaches –200°C. At this temperature it is a liquid. We say that the air has been liquefied. Here's what happens as the air liquefies: water vapour condenses, and is removed using absorbent filters carbon dioxide freezes at –79ºC, and is removed oxygen liquefies at –183ºC nitrogen liquefies at –196ºC The liquid nitrogen and oxygen are then separated by fractional distillation. Liquid oxygen

Testing for oxygen. How would you test a gas to find out if it is oxygen?

Oxy-fuel welding torches. These welding torches use pure oxygen. Why?

Other uses of oxygen.

The metal joins with oxygen Copper Copper oxide To make a solid metal oxide The metal gets heavier after combustion because the oxygen particles have joined with the metal particles to make a compound.

Oxidation – adding oxygen. When a substance chemically combines with oxygen this is an example of an oxidation reaction. Heating magnesium to make magnesium oxide.

Fuels. What is a fuel? A substance that contains energy. Why are fuels burned? To release the energy. What is the name of this type of reaction? Combustion.

So what is in a fuel? Coal contains carbon. Oil and gas are compounds called hydrocarbons. From the name what are the 2 elements found in a hydrocarbon? Hydrogen and carbon. A hydrocarbon is a compound that contains hydrogen and carbon only.

Hydrocarbons.

Investigating the products of combustion. What tests are being carried out to identify the products of combustion? What happens to the mass of the candle?

Complete combustion Hydrocarbon + oxygen  water + carbon dioxide Methane + oxygen  water + carbon CH4 + O2  CO2 + H2O Balanced: CH4 + 2O2  CO2 + 2H2O Explain why combustion reactions are an example of an oxidation reaction?

To make gaseous products. Non-metal fuels join with oxygen This is butane To make gaseous products. The mass of the fuel decreases because the products are gases that diffuse away.

Element or compound? B C D E A 1Label these substances as elements or compounds. carbon dioxide copper chloride zinc sodium hydrogen carbonate hydrogen 2 Label these particle pictures as elements or compounds. B C D E A 3 Label these formulae as elements or compounds. CO2 CO O2 NaCl H2SO4 Cs 4 Which particle pictures show molecules? 5 Which particle picture is both an element and a molecule?

The formula of a compound shows the symbols of the elements it is made from and how many atoms of each element there are. H2O hydrogen 2 atoms oxygen 1 atom Formulas show all the atoms in a molecule. NaCl 1 sodium atom for every 1 chlorine atom or the ratio of atoms

Understanding formulae Draw particle diagrams for the following compounds; carbon dioxide CO2, carbon monoxide CO, sulfur dioxide SO2, nitrogen monoxide NO, nitrogen dioxide NO2 and water H2O. The first one has been drawn for you. O C O

Counting atoms. Could you draw a particle picture of this compound?

When a compound is made from two elements. Lithium Calcium The first part of the name is the name of the metal element. The non-metal element makes the last part of the name. oxide chloride

Name of element when in a compound Compound names that end in –ate Pyrotechnics Skycolour 3 Illuminate SS6 Naming compounds The first part of the name is the name of the metal element. Metal element Non-metal element Compound potassium chlorine magnesium oxygen sulfur iron sulfide sodium sodium iodide copper bromide sodium fluoride sodium fluorine The non-metal element makes up the last part of the name. But the ending of the non-metal element is changed to – ide. Complete the tables: Non-metal element Name of element when in a compound fluorine fluoride chlorine chloride oxide sulfur bromide iodine phosphide Compound names that end in –ate Contain two elements and oxygen silver nitrogen oxygen silver nitrate Compound Elements calcium carbonate calcium carbon oxygen copper sulphate potassium phosphate 30

Investigation – Iron and sulfur. Mix the iron and sulfur together. Describe what it looks like. Using the equipment provided – how can you separate this mixture? Mix the iron and sulfur together – now heat it for 5 mins. Let the substance cool down and then test to see if it is magnetic. What is the name of the compound you have made?

iron particles Key: one iron particle strong bonds between iron particles iron particles held together by strong bonds

iron particles iron particles are attracted to a magnet iron particles diagram

sulfur particles one sulfur particle Key: one sulfur particle strong bonds between sulfur particles sulfur particles held together by strong bonds

sulfur particles sulfur particles are not attracted to a magnet sulfur particles diagram

iron particles sulfur particles

A mixture of iron and sulfur particles What’s this? A mixture of iron and sulfur particles strong bonds between iron particles strong bonds between sulfur particles

A mixture of iron and sulfur particles A magnet attracts the iron particles but not the sulfur particles. The mixture is separated mixture diagram

A compound between iron and sulfur particles What’s this? A compound between iron and sulfur particles one iron particle one sulfur particle strong bonds between iron and sulfur particles

A compound between iron and sulfur particles strong bonds between iron and sulfur particles The magnet cannot separate iron and sulfur particles in a compound compound diagram

Conclusion: After a chemical reaction has taken place the properties of the reactants and products are different. Reactants (before) Product (after) Iron + sulfur  iron sulfide

Word equations Rules Reactants (starting materials) are on the left-hand side. Products (what is made) are on the right-hand side. An arrow  separates products from the reactants. The + sign is used instead of ‘and’.

Testing understanding. Write word equations for the 3 reactions described below. 1. Magnesium metal burns in oxygen gas with a bright white light to make a white powder called magnesium oxide. 2. A solution of sodium iodide is added to a solution of potassium nitrate to make a potassium iodide precipitate and a sodium nitrate solution. 3. Gaseous hydrogen and gaseous oxygen react explosively to form water vapor.

Answers 1. Magnesium + oxygen  magnesium oxide 2. Sodium iodide + potassium nitrate  potassium iodide + sodium nitrate 3. Hydrogen + oxygen  water What is the correct name for water? Which 3 atoms are found in sodium nitrate?

Chemical reactions. During a chemical reaction no new atoms are added and none are lost they are simply rearranged.

Writing balanced symbol equations. 1. The number of each type of atom must be equal for each side of the reaction. 2. The formula can’t be changed e.g. CO2 is always CO2 3. Only the number in front of the formula can change.

Complete combustion Hydrocarbon + oxygen  water + carbon dioxide Methane + oxygen  water + carbon CH4 + O2  CO2 + H2O Balanced: CH4 + 2O2  CO2 + 2H2O

Another example!

2 Mg + O2  MgO 2  Symbols Mg + O2

2 Al + I2  AlI3 3 1½ 2  Symbols Al + I2

Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 Ca + H2O NaOH + H2SO4 CH3OH + O2 MgO ZnCl2 + H2 FeCl3 NaCl + H2O CO2 + H2O Ca(OH)2 + H2 Na2SO4 + H2O 2 2 4

Are humans to blame for pollution? Human activity Natural processes

What is a pollutant? Pollutants are directly harmful to humans, and some that are harmful to the environment and so cause harm to humans indirectly. Can you give examples of both?

Some sources of pollution.

Pollutants. The common pollutants found in air are: 1. Carbon monoxide. 2. Oxides of nitrogen. 3. Sulfur dioxide. 4. Particulates of carbon. 1. Carbon dioxide indirectly harms us. Checking exhaust emissions

Carbon monoxide. Causes – incomplete combustion of petrol or diesel (hydrocarbons) in car engines. Effect – a poisonous gas.

Carbon monoxide and volume of traffic. What is the connection between amount of traffic and the concentration of carbon monoxide?

Oxides of nitrogen. Causes – formed in the internal combustion engine. Effect – photochemical smog and acid rain.

Emissions of Nitrous oxides

Sulfur dioxide Causes – formed when sulfur impurities in fossil fuels burn. Found in coal which is used in power stations. Effects – acid rain kills plants, aquatic life, erode stonework and corrode metals.

Emissions of sulfur dioxide. How does this compare with the map for Nitrous oxides?

Formation of acid rain.

Effects of acid rain

Particulates of carbon. Particulate carbon is deposited on surfaces, making them dirty.

What happens to the carbon dioxide? 1. Carbon dioxide is used by plants in photosynthesis. 2. Carbon dioxide dissolves in rain water and in sea water.

What fuels do power stations use? The 3 fossil fuels are; Coal Oil Gas What pollutants do they produce?

Pollutants produced by power stations The pollutants are: 1. Sulfur dioxide. 2. Particulates of carbon. 3. Carbon monoxide 1. Carbon dioxide indirectly harms us.

Reducing pollutants from power stations. Remove sulfur dioxide and carbon from flue gas emissions. Use less electricity. Remove sulfur from natural gas and fuel oil.

Incomplete combustion. Incomplete combustion occurs when there is not enough oxygen. What would you observe if incomplete combustion is taking place?

Understanding incomplete combustion. Which balanced equation represents complete combustion and which represents incomplete combustion? What do you notice about the amount of oxygen in each reaction? 1 2

Neutralising the acidic gas. When wet scrubbing with a Ca(OH)2 (lime) slurry, the reaction also produces CaSO3 (calcium sulfite ) and can be expressed as: Ca(OH)2 + SO2 → CaSO3 + H2O Alkali Acid Salt Water

Seawater absorbs sulfur dioxide. A natural alkaline usable to absorb SO2 is seawater. The SO2 is absorbed in the water, and when oxygen is added reacts to form sulfate ions SO4- and free H+

What pollutants are produced by a car engine? The pollutants are: 1. Carbon monoxide. 2. Oxides of nitrogen. 3. Sulfur dioxide. 4. Particulates of carbon. 1. Carbon dioxide indirectly harms us.

Formation of Nitrogen Oxides Nitrogen monoxide NO is formed during the combustion of fuels in air and is subsequently oxidised to nitrogen dioxide NO2 . What type of reaction is this? Oxidation – oxygen is added.

What happens to the nitrogen oxides?

Reducing pollutants from car emissions. More efficient engines. More public transport. Use catalytic convertors. Remove sulfur from fuel. Legal limits on car Emissions – checked by MOT tests.

Financial incentives: Task: Read p.53 Foundation or p.61 Higher of textbook. What are the 3 ways that the UK government has used to encourage people to produce less pollution. Then answer Q.2

Catalytic converter

What does a catalytic converter do? After Before What happens to the carbon monoxide (CO) and nitrogen oxides (NOx )? Hint – oxidation/reduction.

What does a catalytic converter do? A catalytic converter oxidises carbon monoxide into carbon dioxide. It also reduces nitrogen oxide into nitrogen and oxygen.

What happens inside the converter. 2NO => N2 + O2 or 2NO2 => N2 + 2O2 This is a reduction reaction. The reduction catalyst is the first stage of the catalytic converter. The oxidation catalyst is the second stage of the catalytic converter. 2CO + O2 => 2CO2 This is an oxidation reaction.

Biofuels. What are the problems and benefits of using biofuels as an alternative to petrol and diesel? Have a go at the update activity.

Electric cars – as an alternative. What are the problems and benefits of using electricity as an alternative to petrol and diesel? Hint – think about how the electricity might be generated.

Is there a pattern when hay fever occurs? Discover. You will analyse some data in order to answer the question above. The key skill you will use is; Examine patterns and relationships.

Describe any pattern in the data? Why would a graph be useful? Why has the investigation being repeated?

What does correlation mean? Correlation measures how strong is the link between the factor and the outcome. Which of the graphs opposite shows the strongest link – greatest correlation? How did you tell?

Strong correlation.

Be very careful! Not all links between factor and outcome means one causes the other.

What do you need? The key to any correlation is the EVIDENCE. If the evidence is good and links the factor to the outcome then a strong scientific claim can be made.

A reliable claim. This evidence must be checked by other scientists – repeated – making it reliable