The document outlines a chemistry route map for studying various topics over 24 lessons, including alkanes, alcohols, carboxylic acids, esters, fats and oils, energy changes, chromatography, titrations, reaction rates, equilibrium, the chemical industry, and green chemistry. It provides lesson objectives, activities, and questions for lessons on alkanes, alcohols, and carboxylic acids, covering topics like their structures, properties, reactions, uses, and how they are produced.

1. C7 Chemistry ‘triple science’ Route map Over the next 24 lessons you will study : Friday 21 October 2011 C7.1 The alkanes C7.2 The alcohols C7.3 Carboxylic acids C7.4 Esters End of module test C7.5 Fats and oils C7.7 Energy changes C7.15 Chromatography C7.16 Interpretating chromatograms C7.17 Gas chromatography C7.18 Titrations C7.8 How much energy C7.9 How fast...rates of reaction C7.10 Reversible changes C7.11 Equilibrium C7.19 Precision and accuracy C7.20 Overview of the chemical industry C7.21 Green chemistry C7.22 Improving yield in industrial chemistry C7.12 Theories on acidity C7.13 Stages in analysis C7.23 Making industrial chemistry greener C7.24 Reducing waste in industrial chemistry C7.6 fats and human health C7.14 Sampling C7.25 Using by-products and reducing waste C7.26 Making ethanoic acid

3. C7.1 The alkanes Extension questions: 1: Name the following alkane a) CH 4 b) C 3 H 8 and c) C 5 H 12 ? 2: As the size of the alkane chain increase so does its boiling point of methane (CH 4 ) is -164 o C, the boiling point of ethane (C 2 H 6 ) -89 o C is predict the boiling point of propane CH 3 H 8 ? 3: What type of bonds are between Carbon and hydrogen ? 4: Write a balanced equation for the combustion of CH 4 and O 2 ? 5: Alkanes with over 17 carbon atoms are solids. Explain the minimum number you would find in carbon atoms in wax ? Know this: a: Know that the alkanes contain just two elements, hydrogen and water. b: Know the chemical and physical properties of the alkanes. Friday 21 October 2011 Introduction: The alkanes have a general formula of C n H 2n + 2 and are used mainly as fuels for combustion with oxygen. They include methane (natural gas), the simplest alkane with the formula CH 4 . Alkanes can have up to 300 carbon atoms in a long carbon chain, but their general formula does not change. Longer chains are used for to make petrol, diesel, lubricating oils and domestic heating fuels. Alkanes with more than 100 carbon atoms are found in bitumen or tar used to make tarmac found on road surface. Alkanes will not react with an acid or alkaline because the C-H and C-C bonds are un-reactive.

4. Key concepts C7.1 a Look at the photograph and information and answer all the questions: Alkanes like methane, ethane, propane, butane and octane are separated and extracted using fractional distillation from crude oil, a thick dark black liquid rich in different hydrocarbon chains When these fuels are combusted with oxygen, energy in the form of heat and light is released. The products of the complete combustion of an alkane are water and carbon dioxide. Loom at the diagram opposite left draw the space filling and structure formula for pentane C 5 H 10 and decane C 10 H 22 ? Write a balanced equation for the combustion of methane CH 4 ? What happens to their a) boiling point and b) viscosity as the number of carbons increase in the chain length ? Alkane (space filling model) Alkane (structure formula) Methane CH 4 Propane C 3 H 8 Ethane C 2 H 6 Butane C 4 H 10

5. Key concepts C7.1 b Look at the photograph and information and answer all the questions: Suggest one or more products of incomplete combustion of methane ? Carbon dioxide gas is one of the products of combustion of an alkane. What effects does rising carbon dioxide gas levels have in our atmosphere ? Methane is rich in carbon and is a store of ancient chemical energy. During its combustion with oxygen, it releases its energy in the form of heat and light. The methane (CH 4 ) molecules breaks apart and forms new bonds with the oxygen atoms. The products of methane combustion with oxygen are water (H 2 O) and carbon dioxide. (C0 2 ) If there is not enough oxygen carbon monoxide can form. Substrates During the reaction Products C O O O O H H H C0 2 H 2 O H 2 O H O 2 O 2 CH 4

6. C7.1 c Look at the photograph and information and answer all the questions: An engine works by combusting octane (C 8 H 18 ) with oxygen (O 2 ). The fuel/air mixture is pulled into a cylinder, A spark ignites the mixture to create combustion to thrust the piston downward and the car forward. If combustion was complete are there were no nitrogen or sulphur impurities in the petrol, the only products would be carbon dioxide and water. What two elements do all hydrocarbons like methane, butane and octane contain ? How does a) carbon monoxide and b) carbon particulates affect human health and in particular the lungs ? Explain why all cars have to undergo a yearly emissions test as part of the vehicle MOT which test the level of these polluting gases ? Key concepts octane + oxygen carbon dioxide + Substrates Products water Combustion of the Alkanes

7. C7.1 Plenary Lesson summary: eight fuels hydrogen alkanes Friday 21 October 2011 Carbon is a very interesting element: Carbon is the basis for organic chemistry, as it occurs in all living organisms. Carbon is a non-metal that can bond with itself and many other elements, forming nearly ten million compounds. Elemental carbon can take the form of one of the hardest substances (diamond) or one of the softest (graphite). How Science Works: Research into alcohols. What is their common formula, what are they used for and how are they made. Preparing for the next lesson: Many common ____ contain a mixture of ________, for example petrol contains about 80% octane. This hydrocarbon has a formula C 8 H 18 showing us the presence of ______ carbon atoms and 18 _________ atoms.. Decide whether the following statements are true or false : False True 3: As the number of carbon atoms increase so does their melting points ? False True 2: The alkanes are used mainly as fuels for example octane is found in petrol ? False True 1: Methane has the formula CH 4 and decane has the formula C 8 H 18 ?

9. C7.2 The alcohols Extension questions: 1: Alcohols are good at dissolving fats, why does this make them useful in the car industry ? 2: Ethanol used in bio-fuels can be fermented form corn starch or made using fossil fuels. Which type of ethanol has the least impact in the environment ? 3: Write a balanced equation for the reaction between a) methanol and sodium and b) ethanol and sodium? 4: As you increase the number of carbon atoms in an alcohol would you expect the boiling point to rise or fall…explain your answer ? Know this: a: Know the physical and chemical properties of alcohols. b: Know the different reactions of the alcohols. Friday 21 October 2011 Introduction: The most commonly used alcohol is ethanol, C 2 H 5 OH. Ethanol has been produced and consumed by humans for millennia in alcoholic drinks. It is a clear flammable liquid that boils at 78.4 °C, which is used as an industrial solvent, car fuel, and raw material. The simplest alcohol is methanol CH 3 OH. It is a clear liquid resembling ethanol in smell and properties, with a slightly lower boiling point (64.7 °C), and is used mainly as a solvent, and fuel. Unlike ethanol, methanol is extremely toxic: one sip can cause permanent blindness The hydroxyl group generally makes the alcohol molecule polar. Alcohols, like water, can show either acidic or basic properties. Alcohols react with strong bases such as sodium hydroxide or reactive metals such as sodium. The salts that result are called alkoxides ,

10. Key concepts C7.2 a Look at the photograph and information and answer all the questions: Propane (C 3 H 8 ) has a boiling point of -42.4 o C. Suggest the boiling point for propanol (C 2 H 5 OH) and explain the difference ? Explain why alcohols with longer carbon chains (e.g. hexanol C 6 H 13 OH) do not mix as well in water as alcohols like ethanol (C 2 H 5 OH) All alcohols have a O-H functional group. Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons. The boiling point of the alcohol ethanol is 78.3 °C (C 2 H 5 OH), compared to -89.0 °C for ethane (C 2 H 6 ) Alcohols, like water, can show either acidic or basic properties at the O-H group. They are still able to react with strong bases such as sodium hydride or reactive metals such as sodium. The salts that result are called alkoxides, with the general formula RO- M+. Alcohol (space filling model) Alcohol (structure formula) Methanol CH 3 OH Propanol C 3 H 7 OH Ethanol C 2 H 5 OH

11. Key concepts Look at the photograph and information and answer all the questions: Describe the ideal conditions for fermentation to take place ? Over the next 50 years the governments hopes to increase the amount of bio-ethanol used to power cars and lorries,. Why is bio-ethanol described as carbon neutral ? Land used for producing bio-ethanol cannot be used to grow crops for the human food chain....why might this make our food more expensive in the future ? C7.2 b Making alcohol to drink or to be used as an alternative to petrol involves fermenting the sugar found in plant biomass and distilling it to ethanol. Enzymes found in yeast microbes break down plant starch or cellulose into sugars which then undergo microbial fermentation. The end product is distilled to ethanol. The first record of humans making and drinking alcohol is around 8000 years ago ! Ethanol fermentation ethanol in drinks ethanol used in bio-fuels

12. C7.2 Plenary Lesson summary: alcoholic sodium solvent used Friday 21 October 2011 Alcohol is the waste produced by yeast when they metabolise sugars. The waste builds up in the fermenting mass until it is too poisonous for them to continue to metabolise. Almost every culture has developed a way to make consumable alcohol from anything they have handy. We make it from grain and grapes, the Japanese from rice, and the Mongolians from fermented Yak's milk. How Science Works: Research into the physical and chemical properties of carboxylic acids. Preparing for the next lesson: Ethanol is the most widely ______ alcohol an can be used in _________ drinks, as a fuel and a _________ or degreaser. The alcohols are polar molecules that will react with metals like ________. They can also be either basic or alkaline. Decide whether the following statements are true or false : False True 3: Ethanol because it is polar will have a higher boiling point that ethane ? False True 2: Alcohols are good solvent of both poplar and non polar molecules ? False True 1: The formula of ethanol is C 3 H 7 OH ?

14. C7.3 The carboxylic acids Extension questions: 1: Write a balanced equation (using formulae) for the reactions between zinc and methanoic acid (CHOOH) and calcium hydroxide (CaOH) and ethanoic acid (CH 3 COOH) ? 2: Explain how vinegar (ethanoic acid) keeps food form going off ? 3: Explain why you could not use ordinary hydrochloric acid to preserve foodstuff like onions and gherkins ? 4: Write a) the formula and b) the structure formula for propanoic acid and butanoic acid ? Know this: a: Know the structure, chemical and physical properties of carboxylic acids. b: Know that carboxylic acids are weak acids and as such can be used to preserve food stuffs. Friday 21 October 2011 Introduction: Carboxylic acids are very polar acidic compounds with a COOH functional group. Carboxylic acids has a higher melting point than a different type of organic compound with a similar molecular weight, therefore, they are all solids. The compounds with five carbons or less are miscible with water, and those with more than five carbons are insoluble in water. Carboxylic acids are the most acidic of all organic compounds but are still weak acids. Carboxylic acids will react by neutralisation in the following way. Carboxylic acid + metal salt + hydrogen Carboxylic acid + hydroxide salt and water Carboxylic acid + metal carbonate salt + carbon dioxide + water

15. Key concepts C7.3 a Look at the photograph and information and answer all the questions: Vinegar is an acidic liquid produced by allowing ethanol to react with oxygen in the air forming its key ingredient ethanoic acid, (acetic acid) It also may come in a diluted form. Known as vinegar the amount of acid is typically around 20% for pickling. Vinegar has been used since ancient times and is an important element in European, Asian, and other cuisines Both ethanol (alcohol) and ethnaoic acid (vinegar) can be sued to preserve food stuff. Explain why vinegar is the more useful preservative ? Name two weak acids and two strong acids found in the lab or at home ? Why are preserved pickles in vinegar not kept in metal tins...explain using your knowledge of metals and acids ? Ethanoic acid CH 3 COOH Preserving food in vinegar (ethanoic acid)

16. Key concepts Look at the photograph and information and answer all the questions: How would you measure the pH of a solution of methanoic acid and ethanoic acid ? If you are stung by an ant (the sting contains methonic acid) how would you reduce the pain and inflammation ? The carboxyl functional group that characterizes the carboxylic acids is unusual in that it is composed of two functional groups. This functional group is made up of a hydroxyl group bonded to a carbonyl group. It is often written in condensed form as COOH. The effect of these two function groups (C=O and O-H) on the chemical and physical properties so profound that the COOH is treated as a unique functional group in organic chemistry. C7.3 a Carboxylic acid (space filling model) Carboxylic acid (structure formula) Methanoic acid CHCOOH Propanoic acid C 2 H 5 COOH Ethanoic acid CH 3 COOH

17. C7.3 Plenary Lesson summary: partially ionise water weak Friday 21 October 2011 Formic acid is the simplest organic acid, present in large quantities in animal and plant life. It is a clear liquid with a sharp acidic smell. It is manufactured from carbon monoxide and water. Formic acid is present in the nature as a natural substance. The ants use it in their defence and alarm systems, and it is also found in plants such as the common stinging nettle . How Science Works: Research into ester and how esters are made by reacting an alcohol with a carboxylic acid. Look into what esters are used for form food flavourings to ingredients found in perfumes. Preparing for the next lesson: Carboxylic acids _______ to produce hydrogen ions when dissolved in ________. They only _________ ionise, which means that unlike sulphuric and hydrochloric acid which are very strong acids, they are _______ acids. Decide whether the following statements are true or false : False True 3: Carboxylic acids will neutralise alklaine like sodium hydoxide ? False True 2: Methanoic acid is found in vinegar ? False True 1: Carboxylic acids have a double function group C=) and O-H ?

19. C7.4 Esters Extension questions: 1: Explain what ester you would make if you react methanoic acid with propanol ? 2: During the synthesis of an ester form an alcohol and a carboxylic acid explain the purpose of a) refluxing the two substrates b) the condenser c) the acid catalysts d) the drying agent calcium chloride? 3: If you started with 30 g of ethanol and 40 g of ethanoic acid and got 50 g of ethyl ethanoate. What is the a) theoretical yield for this reaction and the percentage yield ? 4: List three fruits that naturally contain esters ? Know this: a: Know how to make an ester form a carboxylic acid and an alcohol. b: Know that making esters require using the reflux method of organic synthesis. Friday 21 October 2011 Introduction: Esters are compounds formed from the reaction between alcohols and acids. confined to esters of organic acids They have the functional group, RCOOR' where R can be hydrogen or an organic group like CH 3 : Esters are widely used for food flavourings and for making female perfumes. Many of the esters used by chemists are 'nature-identical', that is synthetic versions of naturally occurring esters. Esters can also be used as a ‘plasticisers’ to make PVC soft when used to make children’s toys

20. Key concepts C7.4 a Look at the photograph and information and answer all the questions: Look at the space filling models and structural formula for the three esters opposite left. Dar both for the next ester in the series Methyl pentanoate ? Look at the structural formula of ester would you expect esters to be acid like carboxylic acids ? The functional group that characterises esters is the RCOOR’. Esters are less polar than alcohols. They participate in hydrogen bonds as hydrogen-bond acceptors, but cannot act as hydrogen-bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonding means they are slightly eater soluble. Esters are sweet smelling and highly volatile, due to the fact that they do not self-associate. Consequently esters are more volatile than carboxylic acids of similar molecular weight. Ester (space filling model) Ester (structural formula) Methyl ethanoate CH 3 COOCH 2 CH 3 Methyl propanoate CH 3 COOCH 2 C 2 H 5 Methyl butanoate CH 3 COOCH 2 C 3 H 7

21. Key concepts C7.4 b Look at the photograph and information and answer all the questions: Explain the role of reflux in trying to improve the yield of the ester product ? Explain how the condenser work in this experiment ? An ester can be made by reacting a carboxylic acid with an alcohol in the presence of a dehydrating agent R 1 COOH + R 2 OH R 1 COOR 2 + H 2 O Strong acids, typically sulfuric acid, catalyze this reaction. Many other acids are also used. Esterification is highly reversible. The yield which is normally only 50 to 60% of the product may be improved by using reflux where substrates are recycled during the reaction ester vapour substrates heat ester condenser substrates heat Making esters using the reflux method

22. C7.4 Plenary Lesson summary: ester yield strong alcohol Friday 21 October 2011 Esters are widespread in nature and are widely used in industry. In nature, fats are generally triesters derived from glycerol and fatty acids. Several billion kilograms of polyesters are produced industrially annually and used to make clothing and many other products. How Science Works: Research into fats and oils and understand the differences between saturated and unsaturated fats. Preparing for the next lesson: An ___________ can react with a carboxylic acid to make an _______ This reaction is catalysed by a _________ acid like H 2 SO 4 . The ester ________ can be improved by using reflux where the two substrates are continually recycled during the reaction. Decide whether the following statements are true or false : False True 3: If you react methanoic acid with ethanol the ester will be methyl propanoate ? False True 2: An ester is volatile and will easily evaporate ? False True 1: All esters have a ammonia like smell ?

24. C7.5 Fats and oils Extension questions: 1: Which have the lower melting points an oil or a fat ? 2: Name three food rich in fats or oils from a) animals fats ad b) plant oils ? 3: Do fats mix with a) water and b) alcohols ? 4: Fats can be heated with a strong alkaline like sodium hydroxide to to make which product ? 5: What disease of the circulatory system are saturated fats linked to and which fats are said to protect our hearts? Know this: a: Know the structure and properties of fats and oils. b: Know the difference between a saturated and unsaturated fat or oil. Friday 21 October 2011 Introduction: Fats and oils are large molecules found in the diet form both animal and plant sources. Their role in the human body is as a long term energy store, to keep us warm and also as a starting compound in the manufacture of some hormones including testosterone. Fats and oils are made form an alcohol (glycerol) attached to three carboxylic acids by an ester linkage. The carboxylic acids in fats are sometimes called fatty acids owing to their presence in fats. The difference between oils and fats lies in their melting temperatures rather than in any fundamental structural difference.

25. Key concepts C7.5 a Look at the photograph and information and answer all the questions: Saturated fatty acids are the type of fat that is found in foods from animals, e.g. meat, butter, cheese and cream. Many baked goods such as cakes, biscuits and pastries are also high in saturated fat. Excessive intake of saturated fat can increase blood cholesterol levels, one of the major risk factors for heart disease. Saturated fatty acids are usually solid at room temperature. Name three foods that are rich in saturated fats ? Are foods with so called ‘trans fats’ good or bad for our health ? Describe the difference between a saturated and unsaturated fat ? Saturated fatty acid

26. Key concepts C7.5 b Look at the photograph and information and answer all the questions: Unsaturated fatty acids are found in most types of nuts, avocado pears and plant oils,. Unsaturated fatty acids do not raise blood cholesterol and evidence shows that they may also help to reduce blood cholesterol levels if they replace saturated fat in the diet. Unsaturated fats tend to be liquid at room temperature and sometimes are known as "good fats". Unsaturated fatty acid Name three foods that are rich in unsaturated fats ? Why are plant oils with their lower melting points said to be better at travelling around are circulatory system and if you compared the French death rates in the dry south where olive oil is used and the wet north where butter is used would you expect to find a difference in death from heart disease and other circulatory diseases ? Plant oils

27. Key concepts C7.5 c Look at the photograph and information and answer all the questions: Margarine was once considered a cheap alterative to butter, now it is rebranded as part of a healthy lifestyle rich in what type of fats ? Explain why a person who has suffered a heart attack should lower they total intake of fats in their diet ? Margarine is a purely synthetic product manufactured from using a series of chemical reactions. It was first developed in 1859 as an cheap alterative to butter. The raw materials are a variety of natural oils including rapeseed, palm and sunflower seed oils. The oils are extracted and them chemically changed by a process called hydrogenation. This increases the thickness and melting point of the margarine spread. Further impurities are removed using aqueous sodium hydroxide to neutralise free acids and steam which removes any volatile compounds. Fats and oils Rape seed Palm nut Sunflower seed

28. C7.5 Plenary Lesson summary: rich saturated solid oils Friday 21 October 2011 Soap is made by reacting an acid (oils and fats, such as sunflower and olive oils, are acids) with an alkali (sodium hydroxide otherwise known as lye). It is important not to have too much oil or your soap will be greasy and unpleasant to use. Conversely if you have too much lye the soap will be caustic and could burn anyone who tries to use it. How Science Works: Research into the role of fat in the diet in promoting high blood cholesterol, high blood pressure atherosclerosis and heart disease. Preparing for the next lesson: Animal fats are generally ________ at room temperature. They also have a high percentage of __________ fats which increase blood cholesterol and case heart disease. Plant _____ are usually liquid at room temperature are _____ in unsaturated fats and are healthier when consumed in our diets . Decide whether the following statements are true or false : False True 3: A fat is made form an alcohol and three carboxylic acids joined by a ester link ? False True 2: Plant oils are rich in omega 3 and 6 oils ? False True 1: Trans and saturated fats are when consumed not linked to heart disease ?

30. Extension questions: 1: Why is arthrosclerosis much more likely to develop in an artery ? 2: In the second stage, raised blood pressure and reduced blood flow occurs, what is this condition known as ? 3: What type of fats in the diet are associated with increase the risk of promoting atherosclerosis in humans ? 4: You are the health minister for England and you want to reduce heart disease death rates in the population. Put to together a brief action plan on how you would succeed ? NB: Consider a) education, use of taxation, information campaigns, using prescription drugs and the NHS ? Know this: a: Know that a high fat diets is casual of heart disease in humans. b: Know how we can manage lifestyle factors and lifestyle disease. Friday 21 October 2011 Introduction: Disease of the heart and blood vessels are known as cardiovascular diseases or CVD. They are responsible for more deaths in the developed world than smoking or excessive alcohol consumption. Virtually unheard of in the 1900s, the largest example of a CVD is atherosclerosis...this is the progressive degeneration of the artery walls. High blood cholesterol Raised blood pressure Fatty deposits C7.6 Dietary fats, oils and human health High fat diet Arteries narrow... heart disease

31. Key concepts C7.6 a Look at the photograph and information and answer all the questions: Myocardial infarction is where a part of the heart muscle suddenly loses its blood supply. If you have an MI, a coronary artery or one of its smaller branches is suddenly blocked. The part of the heart muscle supplied by this artery loses its blood (and oxygen) supply. This part of the heart muscle is at risk of dying unless the blockage is quickly undone. 'infarction' means death of some tissue. Explain what happens to the heart tissue that in downstream of the blocked arteries ? Explain why a blockage that occurs toward the aorta is more life threatening than if the blockage occurs at the very bottom ? What advise would you give if you had a friend who has male relatives that have died from CVD between the ages of 45 and 56 ? Myocardial infarction from narrowing arteries

33. C7.6 c Look at the photograph and information and answer all the questions: Look at the graph left, the association between saturated fat in the diet and death from heart disease is show, but no causal link is proved. After more analysis and further studies, a firmer link between saturated fat and deaths from heart disease can be shown. These studies involved clinical trials and clinical intervention. If you treated a large mixed group of people from the US and Finland with statins which lower blood cholesterol and they showed a reduce incidence of deaths from heart disease would that allow you to make a definite link between the two factors ? A second study looked at the effects of intervention for vulnerable (at risk) people and show that by buying them low fat products and giving them free membership to a gym reduced their risk of heart disease...what would this study tell you ? 800 600 400 200 0 0 5 10 15 20 25 Deaths per 10,000 lives Japan Greece Italy Yugo US Finland Dutch France Negative correlation No correlation Key concepts Dietary fat versus heart disease Sat Fat intake (5)

34. C7.6 Plenary Lesson summary: aneurism lungs three fatty Arteries and (veins) can become blocked by ______ deposits that build up over time in a _______ stage process. This blockage can cause high blood pressure and results in a arterial rupture or __________. The fatty deposits can also break off and block a key artery to the heart, _______ or brain. If you’re male have family members who have died or suffer from heart disease, are unfit and eats lots of animal fats including cholesterol your are not likely to make it to 60. Taking statins, drugs that lower blood cholesterol, exercising and of course eating less fats will prolong your life by about 20 years. How Science Works: Friday 21 October 2011 Research into energy changes that occur during a chemical reaction Preparing for the next lesson: Decide whether the following statements are true or false : False True 3: A high fat diet leads to high blood fat levels which cause narrowed arteries ? False True 2: A high salt and fat diet are risk factors for lung cancer ? False True 1: Death from heart disease increase with age and pose a higher risk for males ?

36. Extension questions: 1: Where else are the terms exo and endo used ? 2: Other than heat energy what other forms of energy can be give out to the surroundings ? 4: Give two examples of chemical reactions that are endothermic and exothermic ? 5: In combustion reactions are the reactants (e.g. methane and oxygen) or products (carbon dioxide and water) more stable ? Are the following reactions endothermic or exothermic a) zinc reacting in acid b) Iron rusting and c) a fire work exploding ? Know this: a: Know that reactions either give out or take in energy to and form the surroundings. b: Know how energy diagrams can show the energy changes that occur during a reaction. Friday 21 October 2011 Introduction. All chemical reactions are accompanied by some form of energy changes. These changes can be very obvious (e.g. coal burning) but can go unnoticed Exothermic Energy is given out Endothermic Energy is absorbed Examples: Exothermic combustion of fuels, respiration (oxidation of glucose) Endothermic photosynthesis C7.7 Energy changes and chemical reactions

37. Key concepts C7.7 a Look at the photograph and information and answer all the questions: Give three example of exothermic and three examples of endothermic reactions ? How could show when two solutions react with one another whether they are exothermic or endothermic ? When ever a change occurs in a ‘system’ there is almost always a energy changes: Reactions that give out energy to their surroundings in the form of heat, light or sound are called exothermic reactions, those that take energy from their surroundings are endothermic reactions. In the experiments that you do, exothermic reactions are more common. Reaction progress Reaction progress Exothermic Endothermic

38. Key concepts C7.7 a Look at the photograph and information and answer all the questions: Look at the enthalpy (energy) diagram opposite left. Is this an example of an endothermic or exothermic reaction ? Explain why energy needs to be first put into the system when the first molecules of CH 4 collide and react with the first few molecules of O 2 ? The energy needed to ‘kick start’ and break apart the bonds in the first few reactant molecules is called the activation energy. This is a small amount of energy which is required to break the bonds of the first few substrate molecules so they can form the reaction products. What allows the reaction to continue is the energy released from the formation of the first few product molecules. CH 4 O 2 H 2 O CO 2 Molecules with stored chemical energy Products Energy from a spark or heat source kick starts the reaction Activation energy Potential energy Reaction progress Net energy released during reaction Substrates

39. C7.7 Plenary Lesson summary: collide products enthalpy reactions Thermo-chemistry is the study of ________ changes of ________ where substrates ________ with one another, bonds are broken and new bonds are formed forming new __________. Energy changes can either be exothermic or endothermic and the value of these changes are always given in kilojoules per mol. Fuels contain carbon and when combusted give out huge amounts of heat, light, sound and kinetic energy. These different energies can be used for heating, moving a car or turning water into steam which then drives a turbine generator producing electrical energy. How Science Works: Friday 21 October 2011 Research into measuring enthalpy changes and how when bonds are broken energy is taken in from the surrounds and when bonds are formed energy is given out to the surroundings Preparing for the next lesson: Decide whether the following statements are true or false : False True 3: The mass of the products and substrates should always be the same ? False True 2: When bonds are broken energy is take in from the surroundings ? False True 1: Photosynthesis is an example of an exothermic reaction ?

41. Extension questions: 1: For the following reaction C 2 H 6 + 2O 2 2CO 2 3H 2 O a) which bonds are broken during the reaction, b) which bonds are formed when the products are formed c) is this an example of an endo or exothermic reaction ? 2: Why is activation energy a good thing when you are at a petrol station filling your car ? 3: Draw an energy level diagram to show an endothermic and exothermic reaction ? Know this: a: Know how energy is taken in from the surroundings to break bonds and given out to the surroundings when bonds are formed. b: Know that energy given out can do useful work. Friday 21 October 2011 Introduction: Most combustion reactions including the formation of water using jus hydrogen and oxygen requires a ‘kick start’ in the form of heat or an ignition spark for the reaction to proceed, even though they are highly exothermic. The energy needed to ‘kick start’ a reaction is called the activation energy . This is a small amount of energy which is required to break the bonds of the first few substrate molecules so they can form the reaction products. What allows the reaction to continue is the energy released from the formation of the first few product molecules. C7.8 How much energy

42. Key concepts C7.8 a Look at the photograph and information and answer all the questions: List the bods broken and new bonds formed when hydrogen and oxygen react with one another to form water ? Why are buses and cars that use hydrogen fuel cells not completely pollution free despite only emitting water where they travel ? A hydrogen fuel cell is an electrochemical cell that uses hydrogen to generate electricity. The hydrogen (split form water using electricity) is combined with oxygen forming water as its waste product. It generates electricity inside a cell through reactions between a the hydrogen and oxygen. Hydrogen fuel cells are now being developed for use by cars and buses. The advantage here is that they are pollution free where they are driven because the only waste gases they emit is water. Potential energy Reaction progress O 2 Products 2H 2 2H 2 O Substrates Energy required to break O=O and 2 H-H bonds Energy given out when 4 O-H bonds form Energy released when water forms Energy diagram for the formation of water

43. Key concepts C7.8 b Look at the photograph and information and answer all the questions: Loot at the diagram above, explain why energy is need to form Hydrazine (N 2 H 4 ) form nitrogen and hydrogen ? If the reaction was reverse, would this be an endothermic or exothermic reaction ? Most reactions that take simple molecules like N 2 and H 2 and build larger product molecules like NH 4 are endothermic meaning they require energy from their surroundings. This energy is normally supplied to the reacting molecules as heat. Photosynthesis where CO 2 and H 2 O are combine to form glucose (C 6 H 12 O 6 ) is a good example of an endothermic reaction Potential energy Reaction progress Products Substrates Activation energy Net energy taken in during reaction N 2 2H 2 N N + 2H H Bonds broken H H H H Bonds formed N N

44. C7.8 Plenary Lesson summary: endothermic give reactions break Friday 21 October 2011 A fuel cell is a device that converts a fuel such as hydrogen, alcohol, gasoline, or methane into electricity directly. A hydrogen fuel cell produces electricity without any pollution, since pure water is the only by product. Hydrogen fuel cells are used in spacecraft and other high-tech applications where a clean, efficient power source is needed. How Science Works: Research into Rates of reaction and how we can measure the rate of reaction between two or more substrates. Preparing for the next lesson: Chemical _______ can be either exothermic if they ______ out energy to their surroundings or ____________ is they take in energy form their surroundings. What decide this is the difference in the energy required to _______ bonds and the energy given out as _____ bonds form in the product molecules. Decide whether the following statements are true or false : False True 3: An energy diagram helps us understand the energy changes that occur ? False True 2: Energy changes during a reaction is measured in kilojoules or joules (J) ? False True 1: The energy released when H 2 and O 2 react is used to generate electricity ?