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
C7.9 How fast…rates of reaction Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand how a ‘successful collisions between substrate molecules results in a chemical reaction and the formation of a new product </li></ul><ul><li>Understand how activate energy can affect the overall rate of reaction </li></ul>We will focus on. Friday 21 October 2011 First activity: Think of two reaction that have a high rate of reaction and two reactions that have a slow rate of reaction ? Literacy: Rates, rate of reaction, chemical kinetics, activation energy, collision theory, collision, spark, heat, ignition, exothermic and endothermic. Numeracy: The rate of reaction between two reacting substrate must be determined by experiment and describes how much product or substrate is produced or used over time. The units are usually gmin -1 or gs -1 . PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
Extension questions: 1: Explain why a spark is required to ignite petrol ? 2: If you compared how you light a gas bunsen burner and a sparkler, which reaction has the higher activation energy and explain how you made that decision ? 3: Explain how washing clothes a) at a higher temperature and b) with double the amount of washing powder ? 4: Explain how enzymes speed up the rate of reaction when breaking food down like proteins, carbohydrates and lipids ? Know this: a: Know how successful collision produce a reaction between colliding substrate molecules. b: Know that the activation energy can affect the overall rate of reaction. Friday 21 October 2011 Introduction: Although collision theory is simple and states that for two or more substrates, they must first collide to form new products. Substrates have to collide with one another in the right way and with sufficient kinetic energy for a successful collision where new products are formed. Take the reaction between methane and oxygen, it is not enough that they collide to react. Bonds in the substrates must first be broken. This needs energy in the form of a heat source of an ignition spark. In any reaction if the activation is high, then fewer molecules will have sufficient energy and the reaction will proceed slowly. If activation is low the rate of reaction, over will be fast. C7.9 How fast…rates of reaction
Key concepts C7.9 a Look at the photograph and information and answer all the questions: Reaction with low activation energies allow more of the substrate molecules to collide successfully resulting in the formation of a new product. This means that the rate of reaction remains high. Reactions with a high activation energy, means that the success rate when substrates molecules collide is much lower meaning that the rate remains low. Give an example of a reaction that is a) fat and b) slow ? Based on the rate of the following reactions do they ace a high or low activation energy a) iron rusting b) respiration of glucose c) combustion of methane ? Respiration in cells is speeded up by enzymes. Look at the diagram opposite left, how do enzymes work when the speed up the rate of a reaction ? Reaction with a low activation energy Reaction with a high activation energy Potential energy Reaction progress Products Substrates Potential energy Reaction progress Products Substrates
C7.9 b Look at the photograph and information and answer all the questions: New products formed during a reaction are accompanied by changes in temperature. This is because energy is transferred to or from the surroundings. Reactions that give out energy to the surroundings like combustion are described as exothermic. Reactions that take in energy from the surroundings like photosynthesis are described as endothermic. Name two everyday reactions that re endothermic and two everyday reactions that are exothermic ? When a rocket is set off an exothermic reaction occurs. Apart from heat and light energy, give two other types of energy that are given out to the surroundings ? Photosynthesis where carbon dioxide and water is combined to form glucose is an endothermic reaction. What is the opposite of this reaction ? Exothermic Endothermic ‘ energy to the surroundings’ ‘ energy from the surroundings’ energy reaction progress energy reaction progress Key concepts substrates substrates products products
Key concepts C7.9 c Look at the photograph and information and answer all the questions: Out of 1000 collisions for the reaction between methane and oxygen, how many would by on average successful ? Explain why it matters how substrates collide (think about what happens when substrates react and the bond that are broken) ? Although collision theory is simple and states that for two or more substrates, they must first collide with sufficient energy to react and form new products, there are right and wrong collisions. During the combustion of methane with oxygen, not all collisions between the methane molecule and oxygen result in a successful reaction and the formation of new products (carbon dioxide and water.) Only one out of three collision as shown by the diagrams above have the correct orientation, so that the two substrates can react forming new products Collision theory
Key concepts C7.9 d Look at the photograph and information and answer all the questions: Give one example where a) heat or temperature b) concentration and c) particle size is used to speed up or slow down a chemical reaction ? Explain why powders are explosive and powders like magnesium or aluminium powder are dangerous if given to students in a laboratory ? Although collision theory is simple and states that for two or more substrates, they must first collide with sufficient energy to react and form new products, there are right and wrong collisions. During the combustion of methane with oxygen, not all collisions between the methane molecule and oxygen result in a successful reaction and the formation of new products (carbon dioxide and water.) Only one out of three collision as shown by the diagrams above have the correct orientation, so that the two substrates can react forming new products
7.9 Plenary Lesson summary: bonds substrates activation concentration Friday 21 October 2011 Gunpowder burns but it burns very quickly. It's very reactive with oxygen. When enough heat is applied, either externally or from itself, the reaction progresses very rapidly and the gunpowder "explodes” producing enough product gases to expel at very high speed a bullet. How Science Works: Research into reversible changes and how factors like temperature concentration and pressure can change which direction a reaction will go. Preparing for the next lesson: The rate of reaction between two colliding __________ can be influenced by the __________ energy required to break the _______ between atoms in the reacting substrates. There are four main factors that affect the rate of reaction: temperature, ____________, particle size and presence of a catalysts Decide whether the following statements are true or false : False True 3: The rate o reaction is always highest at the beginning of a reaction ? False True 2: The rate of reaction cannot be predicted, it must be determined by experiment ? False True 1: Heating reacting molecules give them more kinetic energy ?
C7.10 Reversible changes Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand that some chemical reactions are reversible and go in the forward or reverse direction </li></ul><ul><li>Understand the factors like temperature and pressure can determine the direction of a reversible chemical reaction </li></ul>We will focus on. Friday 21 October 2011 First activity: Thinks about rates and reaction and the effect of temperature explain the following a) why food is placed in the fridge to keep it fresh and b) why do we warm milk and the bacteria lactic bacillus when making yoghurt ? Literacy: Reversible reaction, equilibrium, forward, reverse, change of state, matter, solid, liquid, gas and reversible processes. Numeracy: If you raise the temperature of a reaction by 10 o C it normally double the rate of reaction. This is because for each 10 o C rise in temperature twice as many collisions have sufficient energy to overcome the activation energy. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
Extension questions: 1: Take calcium carbonate with the formula CaCO 3 . If you heat is strongly it will decompose form calcium oxide (CaO) and carbon dioxide gas (CO 2 ) What happens if you cool the calcium oxide in normal air and write an equation for this reaction ? 2: Write an equation to show the reversible reaction between carbon monoxide (CO) and steam (H2O) to form carbon dioxide (CO2)and hydrogen (H 2 ). When you have written your equation describe what is happening a) in the forward direction and b) in the reverse direction ? Know this: a: Know that some reactions can go in the forward and reverse direction b: Know that the direction of a reversible reaction can change depending on the conditions like temperature, pressure and concentration. Friday 21 October 2011 Introduction: Most reactions that we see are not easily reversible and go in one direction, for example the combustion of butane or the rusting or iron. Some chemical reactions are reversible going forwards or backwards depending on the conditions. The direction of a reversible reaction can changed according to the temperature, pressure or concentration. In the reaction below, at room temperature the reaction ammonia gas and hydrogen chloride will form ammonium chloride. NH 3 (g) + HCl (g) NH 4 Cl NH 4 Cl (g) NH 3 (g) + HCl (g) When ammonium chloride is gently heated it will decompose back to ammonia and hydrogen gas. C7.10 Reversible changes
C7.10 a Look at the photograph and information and answer all the questions: Gases, liquids and solids are all made up of particles, but the behaviours of these particles differ in the three phases. Particles in a gas are well separated with no regular arrangement moving freely at high speeds, in a liquid particles are close together with no regular arrangement sliding about one another and in a solid particles are tightly packed, usually in a regular pattern vibrating around a fixed point. Using your knowledge of the properties of solids, liquids and gases, is sand behaving like a solid, liquid or gas ? Explain what happens when you heat a) a solid iron bar and b) a can containing a compressed gas ? Glass from an 11 th century church window was measured to be slightly thicker at the bottom than the top, does this prove that glass can flow like a liquid ? Solid Liquid Gas Key concepts a b c d a melting b freezing c evaporation d condensation Sates of matter
Key concepts C7.10 b Look at the photograph and information and answer all the questions: Give another example of a chemical reaction that goes in a forwards and backwards direction ? If you rescued off the sea bed an old cannon from a ship wreck and is was badly corroded with lots of iron oxide, how could you restore this piece using the above ? In the above example the reaction is fully reversible. The forward direction is favoured when the concentration of steam is very high forming iron oxide and hydrogen gas. The backward direction is favoured when the concentration of hydrogen is high and the concentration of steam is low forming iron from iron oxide and water vapour Forward direction Backward direction Forward direction Steam high Hydrogen low Products Fe 3 O 4 (s) + 4H 2 (g) Backward direction Steam low Hydrogen high Products 3Fe (s) + 4H 2 O (g) Heat Hydrogen Iron Steam Heat Hydrogen Iron Steam
C7.10 Plenary Lesson summary: products oxide reactions temperature Friday 21 October 2011 Did you know that a reversible reaction that is exothermic when going in the forward direction can be encourage further to go in the forwards direction if you cool the substrates. That because the system will do the opposite to produce heat ! How Science Works: Research into when chemical reaction reach equilibrium. Preparing for the next lesson: Some chemical ________ go only in one direction, for example the oxidation of magnesium metal forming magnesium __________. Some reaction can go either direction. The direction they go will depend on the conditions for example the reaction ___________, pressure and even concentration of the substrates or __________. Decide whether the following statements are true or false : False True 3: The reverse reaction of cellular respiration is photosynthesis ? False True 2: Most reactions that we observe in our everyday lives are not reversible ? False True 1: A rust iron object can be restored by passing hydrogen gas over it ?
C7.11 Equilibrium Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand that for a reversible reaction the amount of substrates and products can reach equilibrium </li></ul><ul><li>Understand that at dynamic equilibrium, there is no overall net change of the concentration of substrates and products </li></ul>Friday 21 October 2011 First activity: Ozone and oxygen in the high upper atmosphere are at equilibrium. Ultra violet light, the very thing ozone protects us from, encourages the formation of ozone from oxygen. Write a balance equation for both the forward and reverse direction of ozone form oxygen ? Literacy: Reversible reactions, equilibrium, dynamic equilibrium, forwards, backwards, concentration, temperature and pressure,. Numeracy: When a reaction can go in the forward and backwards direction, yield of product are typically low at around 30 to 40%. Removing the product as it is produced helps improve the yield as well as recycling un-reactants substrate molecules PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
Extension questions: 1: Write balance symbol equation showing the forward and backwards direction for the formation of ammonia (NH 3 ) from hydrogen (H 2 ) and nitrogen (N 2 ) ? 2: The formation of NH 3 is endothermic, what would happen if you heated the reaction system ? 3: Explain why the yield for products of reversible reaction are low ? 4: Give one other example of a reversible reaction ? 5: Why do you need to do the reaction in a sealed test tube ? Know this: a: Know that for reversible reactions the amount of substrate and product reach equilibrium. b: Know that at dynamic equilibrium there is no net change in the concentration of substrates and products. Friday 21 October 2011 Introduction: In closed systems (sealed test tube) a reversible reaction will reach equilibrium with both substrate and product molecules present staying at the same overall net concentration. Example: If you sealed a test tube containing both nitrogen and hydrogen gas and left it a room temperature, slowly ammonia (NH 3 ) would form. Eventually, a dynamic equilibrium would be reached where the concentration of hydrogen (H 2 ) nitrogen (N 2 ) and ammonia will not change. C7.11 Equilibrium
Key concepts C7.11 a Look at the photograph and information and answer all the questions: Describe what happens over time to the concentration of substrates and products ? Why does the rate of change of formation of products or use of substrates slow down over time ? Time (seconds) Substrate concentration Substrates Products Product concentration Time (seconds) Substrates Products Substrate concentration At the beginning of the reversible reaction the concentration of substrates reduces as the concentration of the products increases. The rate at which both substrates and products change concentration begins to slow down. When equilibrium is reached, the net concentration of substrates and reactants do not change, however the forward and back reaction does not stop. The rate for both directions is the same. Changing the temperature or pressure will alter the equilibrium point. Reaching equilibrium At equilibrium
Key concepts C7.11 b Look at the photograph and information and answer all the questions: Explain the difference in the molecules present at the start of the reaction and when dynamic equilibrium is reached ? Why is the production of ammonia, a starting compound for the manufacture of fertilisers so important ? Ammonia which is used to make nitric acid (HNO 3 ) is made by reacting nitrogen and hydrogen. This reaction is very slow and reversible i.e. some of the ammonia that is formed breaks down again to form hydrogen and nitrogen. The first attempts in the late 1800s to make ammonia only yielded very small amounts . N 2 + 3H 2 2NH 3 (g) forwards backwards substrates N 2 + 3H 2 products NH 3 + 3H 2 Dynamic equilibrium
Key concepts C7.11 c Look at the photograph and information and answer all the questions: Describe how the concentration of a) substrates and b) products change over time ? At equilibrium, the reaction goes in the forward and reverse direction, but there is not net change in substrates and products. What is meant by this ? In a closed sealed system containing nitrogen (N 2 ) and hydrogen (H 2 ) molecules, an equilibrium would be reached where ammonia (NH 3 ) and the two substrate molecules nitrogen and hydrogen would also be present. At equilibrium, you might think that the reaction has finished but this is not the case. Some H 2 and N 2 molecules are still reacting to give NH 3 , but they are compensated by NH 3 molecules reacting to form H 2 and N 2 . NH 3 Time (minutes) Concentration of substrates Substrates Products 3H 2 N 2 N 2 + 3H 2 The reaction will reach equilibrium where all three molecules (N 2 H 2 + NH 3 ) exist. 2NH 3 Dynamic equilibrium
Key concepts C7.11 b Look at the photograph and information and answer all the questions: Explain what happens to the rate of reaction between nitrogen and hydrogen gas as you increase the a) pressure and b) temperature of the reaction ? Look at the graph showing the effect of adding a catalysts to the reaction. Explain what happens to the rate of reaction ? The first attempts to make ammonia only yielded very small amounts. Fritz Haber began to experiment to improve the yield and succeeded by using catalysts and changing the temperature and pressure. He discovered the main factors that controlled the yield of ammonia (NH 3 ), which was then used to make fertilisers. These are temperature, pressure and the presence of an iron catalyst. Because of Fritz Haber, modern agriculture is now able to feed all those millions of people who live in the USA and Europe . Changing pressure Changing temperature Using a catalyst % yield of ammonia % yield of ammonia % yield of ammonia 0 Pressure (atms) 200 400 0 Temp ( o C) 300 600 Time (minutes) Catalyst Without catalyst 550 o C 50 o C 400 o C 350 o C 100atms 150atms 200atms 300atms 70 70 70
C7.11 Plenary Lesson summary: yield product substrate net Friday 21 October 2011 Fritz Haber realised, using basic theory, that low temperatures and high pressures would be the right conditions for the highest yield of ammonia, however, the reaction in the forward direction was too slow to be profitable. He came up with the solution of using moderately high temperatures and pressures with an iron catalyst. Although the reaction still didn’t go to completion, the yield of ammonia was high enough to make it viable to then make fertilser. How Science Works: Research into theories of acidity and what makes a strong and weak acid . Preparing for the next lesson: At equilibrium, the concentration of __________ and _________ stay the same with no overall _____ change. In all reversible reactions _______ are low typically around 30 to 40%. Decide whether the following statements are true or false : False True 3: A reversible reaction is indicated by using forward and backward arrows ? False True 2: Most reactions are reversible ? False True 1: Dynamic equilibrium can only be reached in a closed system ?
C7.12 Theories on acidity Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand what is an acid and how it differs from a base </li></ul><ul><li>Understand that strong acid fully ionise in water and weak acids only partially ionise in water </li></ul>We will focus on. Friday 21 October 2011 First activity: Think of three substance that are weakly acidic for example lemon juice and three substances that are strongly acids for example bleach ? Literacy: Acid, base, alkaline, pH, acidity, ionise, strong acid, hydrochloric acid, sulphuric acid, weak acid, properties, carboxylic acid ethanoic acid and buffers. Numeracy: The ph of a weak acid is around 5 to 6, the pH of a strong acid is around 1 to 2. the pH of a neural substance like water is 7. All alkaline have a pH above 7, with the strong base having a pH of around 11 to 13. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
Extension questions: 1: Give the names of two acid and two soluble base found in your kitchen or bathroom at home ? 2: Which is the strong acid: lemon juice pH 5.5 or vinegar pH 5.2 ? 3: Describe the reaction between magnesium (Mg) and hydrochloric acid (HCl) a) what is the metal salt called and b) what is the gas produced called ? 4: Explain how you could test the pH of a) water b) coca cola ? 5: Give two uses for strong acid and two uses of a weak acid ? Know this: a: Know how an acid differs form a soluble base. b: Know what makes an acid either a strong or weak acid. Friday 21 October 2011 Introduction: In the late 1800s, the Swedish scientist Svante Arrhenius suggested that acids are compounds that contain hydrogen and can dissolve in water to release hydrogen ions into solution. For example, hydrochloric acid (HCl) dissolves in water as follows: HCl in H 2 O H+( aq ) + Cl-( aq ) Arrhenius defined bases as substances that dissolve in water to release hydroxide ions (OH-) into solution. NaOH in H 2 O Na+( aq ) + OH-( aq ) Strong acids like H 2 SO 4 HCl are strong acid because all the molecules ionise in water Weak acids like ethanoic acid are weak because only a handful of molecules ionize in water C7.12 Theories on acidity
C7.12 a Look at the photograph and information and answer all the questions: The pH scale is a way of telling us whether a a substance is acidic, neutral or alkaline. Liquids like lemon and tomato juice are acidic. Pure water is neutral and liquids like toothpaste and oven cleaner are alkaline. pH can also tell us how strong an acid or alkaline is, for example strong acids have a pH of 1, strong alkalis have a pH of 13. Give two examples of a substance that is strongly acidic and two examples of substance that are strongly alkaline ? Explain why all toothpastes are made slightly alkaline with a pH of 8 ? A lake has become acidic due to acid rain...explain how you could obtain the lake water’s pH and how would you bring the lake water’s pH back to near neutral ? Key concepts pH 2 pH 3 pH 4 pH 5 pH 6 pH 1 pH 7 pH 12 pH 11 pH 10 pH 9 pH 8 pH 13 pH 7 Battery acid Vinegar Urine Lemon juice Acid rain Tomato juice Pure water Caustic soda Oven cleaner Toothpaste Bleach Baking soda Soapy water Pure water Acids Alkalis
C7.12 b Look at the photograph and information and answer all the questions: Acids are chemicals with very high amounts of hydrogen ions. They will turn litmus paper red. They will also have a pH ranging from 1 to 6 when tested using universal indicator. Acids will also attack materials like metals liberating hydrogen gas and forming a metal salt. Acids are found naturally and have a sour taste, for example lemon juice is rich in citric acid. You have two liquids, both are acids. The pH of liquid A is 2 and the pH of liquid B is 6.5...explain which is the strongest acid ? Explain how the acids contained in vinegar preserve foods like pickled onions over long periods of time ? You spill hydrochloric acid on your skin and clothes...what safety precautions should you have taken and what should you do ? pH 2 pH 3 pH 4 pH 5 pH 6 pH 1 pH 7 Battery acid Vinegar Urine Lemon juice Acid rain Tomato juice Pure water Acids and pH Key concepts
Look at the photograph and information and answer all the questions: A soil’s pH is important because different plants like different soil conditions. Both cranberries and blueberries like weakly acid soil, where as peach varieties like only mildly acidic to neutral soils. Crops like wheat and corn only gown in neutral soils. Soils can become acidic die to acid rain and we can raise the pH of a soil by adding lime and lower it by adding gypsum. A farmer has a field with soil that has a pH of around 5. He wants to grow corn or wheat...should he add lime or gypsum to his field ? A soil’s pH can be affected by acid rain...what are the causes of acid rain ? How do plant and or tree roots help stabilise soil against water and wind erosion ? Key concepts C7.12 c No growth No growth Peaches Fir trees Blueberries Cranberries Corn & wheat pH 2 pH 3 pH 4 pH 5 pH 6 pH 1 pH 7
C7.12 d Look at the photograph and information and answer all the questions: Hair care products are alkaline, why should you not was your hair with soap designed to was skin ? Name one other use for controlling the pH of a process of a product ? 100% acid base 100% Key concepts Buffers in skin and hair care products Acid buffers working by resisting changes in pH when a base is added. This buffer keeps the pH around 5.5 ideal for skin care products How do buffers work ? Most skin an hair care products are pH balanced. This means that they contain a ‘buffer solution’ which prevents changes or large fluctuations in the products pH. An acidic buffer designed for skin or care. commonly made from a weak acid and one of its salts - often a sodium salt. For skin car, since the natural pH of skin is around pH 5.5. An ideal buffer would resist changes in pH keeping the product at pH 5.5 You can change the pH of the buffer solution by changing the ratio of acid to salt, or by choosing a different acid and one of its salts.
C7.12 Plenary Lesson summary: partially weak fully strong Friday 21 October 2011 Working with strong acids is always dangerous, because the H + ion that is contained in the acid will interact with you skin epithelia cells and destroy them leading to an acid burn. Burns caused by an alkaline are far worse, however because alkalis react with the fat layer underneath the living tissue causing much more damage and far worse scarring. How Science Works: Research into chemical analysis and how chemists continually sample, test and control industrial process designed to manufacture bulk qualities of useful products. Preparing for the next lesson: Carboxylic acids are ______ acids because they only ________ ionise in water. Hydrochloric and _________ acid are strong acids because the _______ ionise in water. Decide whether the following statements are true or false : False True 3: A strong acid fully ionises in water making lots of H + ions available ? False True 2: All acids have pH of 8 or above ? False True 1: A buffer is a solution of a weak acid and its salt ?
C7.13 Stages in analysis Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand why chemists sample and how they control the steps in chemical analysis from sampling to the reliability if the results </li></ul><ul><li>Understand that each step of chemical analysis is very carefully controlled </li></ul>Friday 21 October 2011 First activity: Think of an industrial process, for example making polythene from ethene or making other plastic like PVC and polyurethane. At which points form taking the raw material to the finished product would you sample ? Literacy: Chemical analysis, sample, sampling, measuring, qualitative, quantitative, errors, reliability, comparing calculating and predicting Numeracy: During experiments, data that is produce is often repeated to give a reliable average. The data can have a range or spread (highest to lowest) and also an average. The spread of data can tell us how good our data is ! PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
Extension questions: 1: Why would a farmer want to know the quality of the grass that he or she is feeding to their livestock. ? 2: Why would the following tests be done a) the presence of banned drugs in an athletes blood b) the amount of alcohol in a drivers blood c) The concentration of carbon monoxide in a living room d) the amount of sugar in a fizzy drink d) the amount of vitamin c in a multi vitamin pill ? 3: What is the difference between a qualitative and quantitative method ? Know this: a: Know why chemists need to sample and how they sample and determine the composition of a sample . b: Know the chemists ensure that their sampling data is reliable. Friday 21 October 2011 <ul><li>Introduction: </li></ul><ul><li>Chemists often sample and do qualitative analysis to find out the chemical composition of a sample, for example of polluted air from a inner city location. Samples can also be taken to check the progress, purity or yield of chemical produced by an industrial process. Chemists often consider the following: </li></ul><ul><li>How to take the sample </li></ul><ul><li>How to asses the sample’s composition </li></ul><ul><li>How to calculate the concentration of each component </li></ul><ul><li>How to determine the reliability of the results yielded by steps 2 and 3. </li></ul>C7.13 Stages in analysis
Key concepts C7.13 a Look at the photograph and information and answer all the questions: When chemists sample, they will use a qualitative or quantitative analytical method. A qualitative method tells the chemist what is present in a sample for example the presence of a banned drug in an athletes blood. A quantitative sample will tell the chemist how much there is of a chemical compound for example the amount of vitamin C in a soft drink. Which sampling method would you use to determine a) concentration of sodium in drinking water and b) the presence of a banned drug in urine ? Why do chemists often repeat their sample test sometime up to three times ? If you took three samples and tested them in the same way and one sample result didn't match the other what would you do ? Quantitative Qualitative Quantitative tells us how much of a substance here is in a sample Qualitative tells us what chemicals, drugs or compounds there are in a sample Type of chemical analysis
C7.13 b Look at the photograph and information and answer all the questions: Explain why air quality is monitored in large cities such as London ? Describe the main qualitative differences between clean atmosphere and polluted atmosphere ? Key concepts Oxygen (O 2 ) Nitrogen (N 2 ) Water (H 2 O) Ozone (O 3 ) dioxide (CO 2 ) Carbon Oxygen (O 2 ) Nitrogen (N 2 ) Water (H 2 O) Ozone (O 3 ) low level Carbon dioxide (CO 2 ) Sulphur dioxide (SO 2 ) Nitrogen monoxide (NO) Nitrogen dioxide (NO 2 ) Dinitrogen oxide (N 2 O) Carbon monoxide (CO) The present composition of the atmosphere is 79% nitrogen, 20% oxygen, and 1% other gases including carbon dioxide and the Noble gases (Neon, Argon, Krypton & Xenon). Emissions form car exhausts contain toxic gases. These gases are breathed in and transported to all the body's major organs. These pollutants include, carbon monoxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, dinitrogen oxide, sulphur dioxide, low level ozone, and particulates. The most obvious health impact of car emissions is on the respiratory system.
C7.13 Plenary Lesson summary: analysis how store reliable Friday 21 October 2011 In yoghurt making, the raw materials are milk, lactose bacillus bacteria, fruit and other flavouring and preservative. Sampling the yoghurt as the bacteria breaks down the lactose to lactic acid and making sure that at any time the product matches your quality and if it goes wrong can be dumped before being put into containers and transported to shops and supermarkets. How Science Works: Research into qualitative and quantitative chemical analysis. Preparing for the next lesson: Sampling allows chemists to understand what and how much there is of a particular compound in a sample. Chemists need to consider ____ they take the sample, how they ______ the sample, what type of _________ they do and how ________ their sample data is. Decide whether the following statements are true or false : False True 3: Some samples need to be stored at certain temperatures ? False True 2: Reliability of data is not important when sampling ? False True 1: Sampling at key points in any process allows for better end product quality ?
C7.14 Sampling Decide whether the following statements are true or false: We will focus on. Friday 21 October 2011 First activity: 6 grams of chemical A reacted with 10 grams of chemical B to make 4 grams of product C. Calculate the total maximum theoretical yield and the percentage yield using the actual yield ? Numeracy: Sampling the end product can also tell you the percentage yield of your product which is calculated by dividing the actual yield by the total maximum theoretical yield. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers <ul><li>Lesson objectives: </li></ul><ul><li>Understand why chemists sample and the difference between an qualitative and quantitative analytical method </li></ul><ul><li>A case study into the analysis of toothpaste </li></ul>Literacy: Chemical analysis, sample, sampling, measuring, qualitative, quantitative, errors, reliability, comparing calculating and predicting
C7.14 Sampling Extension questions: 1: Give two examples of a homogeneous substance and two examples of a heterogeneous substance ? 2: Which of the following are a) homogenous and b) heterogeneous a) soup b) sponge cake c) steel girder d) car oil e) chocolate bar e) mineral water and f) blood ? 3: If you were testing the content of protein, sugar, fat and salt in a food product like a sandwich a) how would you sample it and b) how would you store the sample ? 4: explain why chemist take more than one sample during testing ? Friday 21 October 2011 Introduction: When a sample is taken for qualitative or quantitative analysis it must be representative. The sample should give a true picture of the material as a whole. Not all material or substances tested are homogeneous throughout, like for example a bar of soap. If the material is not homogenous throughout, for example then several sample should be taken or the entire material should ground and mixed into a solution or paste before sampling. Know this: a: Know why chemists need to sample and how they sample and determine the composition of a sample . b: Know about a case study into skin cream
Key concepts C7.14 a Look at the photograph and information and answer all the questions: Give three examples of a homogenous sample and three examples of a heterogeneous sample ? Explain why taking a melon and making and blending it make good scientific sense if you were analysis the levels of sugar in the melon ? When chemists take a sample, they need to make sure that the sample represent the whole material. There are two types of material, homogenous material which are identical throughout, for example milk and butter and heterogeneous sample for example a chocolate bar. One way to overcome problems associated with heterogeneous samples is to take the entire material, grind the solid to a powder or paste so that it becomes a homogenous sample What type of sample ?
Key concepts C7.14 b Look at the photograph and information and answer all the questions: Toothpaste is used to promote oral hygiene: The aids that remove the dental plaque and food from the teeth, aid in the elimination and/or masking of halitosis, and deliver active ingredients such as fluoride or xylitol to prevent tooth and gum disease. It is important to note that most of the cleaning is done by the mechanical use of the toothbrush, and not by the toothpaste. Fluoride is added to kill mouth bacteria but is also toxic in a large amount if swallowed. Explain why it is important to know how much fluoride you have added ? Suggest why you would sample the raw material, the finished product before it goes into tubes and the product on the shelves ? A sample of toothpaste showed high levels of fluoride…what would you do ? (the toothpaste had not yet been put into tubes) sample size and storage qualitative or quantitative analysis reliability of results sample homogenous or heterogeneous analysis of errors ? Analysis of toothpaste... a case study
Key concepts C7.14 c Look at the photograph and information and answer all the questions: If you sampled Italian mineral water form volcanically active regions what mineral would be in high quantities ? In tap water would the chloride (Cl - ) concentration be higher or lower than the values quoted for typical mineral water ? Mineral water contains dissolved minerals that alter its taste or give it therapeutic value, obtained natural spring. Dissolved substances in the water may include various salts and sulfur compounds. Traditionally, mineral waters were used or consumed at their source, often referred to as "taking the waters" or "taking the cure," at sites such as spas, baths or wells. The term spa was used for a place where the water was consumed and bathed in; bath where the water was used primarily for bathing, therapeutics, or recreation; and well where the water was to be consumed. Calcium (Ca 2+ ) 50 – 60 Nitrate (NO 3 - ) 2 to 10 Magnesium (Mg 2+ ) 20 – 30 Sulphate (SO 4 2- ) 20 to 40 Potassium (K + ) 2-4 Chloride (Cl - ) 5 to 15 typical mineral composition mg/l Sodium (Na + ) 10-15 Bicarbonate (CO 3 2- ) 200 to 400 Analysis of mineral water ....a case study
C7.14 Plenary Lesson summary: blood structure complicated analyze Friday 21 October 2011 Did you know that prior to a simple chemical test for sugar found in the urine of diabetics, clinicians working in hospitals would literally ‘taste’ the urine to see if it had a sweet taste to it or not. Thankfully things have changed and a simple ‘sugar stick test’ can tell a clinician the amount of sugar in your urine. How Science Works: Research into the general principals of thin layer chromatography (TLC). Preparing for the next lesson: Most material samples are heterogeneous meaning they have a changing composition and _________. This makes sampling them more ________ when compared to a homogenous sample like ________ or urine. Chemists often blend or grind heterogeneous samples before they _______ them. Decide whether the following statements are true or false : False True 3: Taking more than one sample and repeating analysis make data more reliable ? False True 2: Blending turns a homogenous to heterogeneous sample ? False True 1: Blood and milk are homogenous substances ?
C7.15 Chromatography Decide whether the following statements are true or false: <ul><li>Lesson objectives: </li></ul><ul><li>Understand the general principles of chromatography </li></ul><ul><li>Understand how paper chromatography works to separate out different molecules </li></ul>We will focus on. Friday 21 October 2011 First activity: Think of three mixtures that could be separated out using chromatography (paper or thin plate) ? Literacy: Chromatography, separation, molecules, size, charge, solubility, mobile phase station phase, aqueous, non aqueous, solute, solvent and solution. Numeracy: A solute is moved by a solvent. How much a solute moves on chromatography paper in a solvent can depend of its size, solubility and even surface charge. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers
C7.15 Chromatography Extension questions: 1: You suspect a will has been forged by a relative. You have five pens form five different relatives and a sample of the will. How would you use chromatography to prove or disprove whether the will had been forged ? 2: Give two advantages to using thin layer chromatography over gels or separating columns ? 3: If you had a substance that did not dissolve in water, what over solvent would you try ? 4: What the difference between the stationary and mobile phase ? Know this: a: Know about the general principals of chromatography. b: Know how molecules are separated on the basis of their size, charge and solubility. Friday 21 October 2011 Introduction: Thin layer chromatography (TLC) uses the size and solubility of a molecules to separate them out on filter paper. The most basic separation is based on the size of the molecule. The large molecules travel far less along the filter paper when compared to the smaller molecules. The overall charge of the molecules can also affect how it is separated. If the molecule has a positive or negative charge associated with it, as is the case with all proteins, peptides, nucleic acids and some carbohydrates, this can also be used to separated out different molecules in a sample
Key concepts C7.15 a Look at the photograph and information and answer all the questions: Look at the picture opposite left. Explain what has happened to the black ink during chromatography and what does this experiment show ? Which colour of ink is made form the smallest molecules and which is made form the largest molecules ? <ul><li>Paper chromatography illustrates simply how this technique works. </li></ul><ul><li>A drop of mixture is placed in one corner of a square of absorbent paper. One edge of the paper is immersed in a solvent. </li></ul><ul><li>The solvent migrates up the sheet by capillary attraction. As it does so, the substances in the drop are carried along at different rates. </li></ul><ul><li>Each compound migrates at a rate that reflects the size of its molecule and its solubility in the solvent </li></ul>Ink chromatogram
Key concepts C7.15 b Look at the photograph and information and answer all the questions: Scientists ran a sample of Ben Johnson blood against lots of different banned drugs. Why did they do this and which method could they have used ? Why are athletes tested both in and out of season for the presence of banned drugs like steroids ? On September 24 th , Ben Johnson, the 100m sprinter beat Lewis in the 100m final at the Olympics, lowering his own world record to 9.79 seconds. Johnson would later remark that he would have been even faster had he not raised his hand in the air just before he finished the race. However, Johnson's urine samples were found to contain a banned steroid and he was disqualified three days later. He later admitted having used steroids when he ran his 1987 world record, which caused the IAAF to rescind that record as well. Carl Lewis: Previous 100m record holder: Promoted to first place when found to be clear of any drugs during the 1988 Olympics Ben Johnson: Broke the previous 100m record with a time of 9.79 tested positive for banned steroids and eliminated from the 100 m results
C7.15 Plenary Lesson summary: smaller larger size separated Friday 21 October 2011 Scientists who want to recreate how old dyes, pigments and inks were made by early man now use high tech chromatography to find out what different pigments were used to make these ancient inks. By looking at both what’s in the old inks they can recreate some of the colour that early man used to pain cave walls. How Science Works: Research into using two way chromatography and using different solvents with different solutes Preparing for the next lesson: Paper chromatography uses the _____ and solubility of a molecules to ________ them out on filter paper. The most basic separation is based on the size of the molecule. The ________ molecules travel far less along the filter paper when compared to the __________ molecules Decide whether the following statements are true or false : False True 3: Chromatography is ideal for separating sand from water ? False True 2: A good solvent for non polar solutes is ethanol ? False True 1: Large molecules are generally more soluble than smaller molecules ?
C7.16 Interpreting chromatograms Decide whether the following statements are true or false: We will focus on. Friday 21 October 2011 First activity: A sample when run separated into two spots. Spot A is coloured spot B is clear. What could you do to located the colourless spot ? Numeracy: The retardation factor R f can be worked out by dividing the distance move by the sample chemical by the distance move by the solvent. Values are always between 0 and 1. PLTS Independent enquirers Creative thinkers Reflective learners We will focus on Team workers Effective participators Self managers <ul><li>Lesson objectives: </li></ul><ul><li>Understand how chromatography works to separate out different molecules, from inks to drugs to other chemical. </li></ul><ul><li>Understand how to interpret chromatographs and work out the retardation factor (R f ) for a substance </li></ul>Literacy: Chromatography, separation, molecules, size, charge, solubility, mobile phase station phase, aqueous, non aqueous, solute, solvent and solution.
Extension questions: 1: Why is important a) to choose the right solvent to dissolve the sample chemical in and b) to allow the sample spot on the paper/plate to dry before running the solvent ? 2: Give two examples of solvent used to separate out chemicals ? 3: If you write on the paper chromatogram why should you write in pencil and not pen ? 4: Why should you not let the solvent run over the length of the paper or plate chromatogram ? Know this: a: Know how chromatography work by separating out different chemicals. b: Know how to interpret a chromatogram. Friday 21 October 2011 Introduction: Successful technique in chromatograph requires knowledge of the following areas: Preparing the chromatograph (paper or plate): The sample is dissolved in a small volume of solvent and then carefully spotted onto the plate or paper and allowed to dry. Reference material can also be spotted on the same plate at this point Running the chromatogram: The plate or paper is then placed in a solvent in an enclosed chamber. The solvent is allowed to run close to the opposite edge. It I then taken out and dried Identifying where samples have separated to: In coloured sample identifying how the sample have separated is easy, on colourless sample an appropriate dye needs to be used Interpreting chromatograms: Chemical can be indentified against reference sample which are known or by looking at the retardation factor. C7.16 Interpreting chromatograms
Key concepts C7.16 a Look at the photograph and information and answer all the questions: What solvent could be used on a) a non permanent marker and b) a permanent marker pen ? Calculate the distance travelled by a) the solvent b) the blue ink and c) the red ink ? <ul><li>Paper chromatography illustrates simply how this technique works. </li></ul><ul><li>A drop of mixture is placed in one corner of a square of absorbent paper. One edge of the paper is immersed in a solvent. </li></ul><ul><li>The solvent migrates up the sheet by capillary attraction. As it does so, the substances in the drop are carried along at different rates. </li></ul><ul><li>Each compound migrates at a rate that reflects the size of its molecule and </li></ul><ul><li>its solubility in the solvent </li></ul>0 1.1 2.3 2.9 4.1 5.0 (cm) Paper chromatography of inks
Key concepts Look at the photograph and information and answer all the questions: Some compounds have no colour, therefore locating these sample once they have been separated using thin layer chromatography is impossible unless the paper or plate is treated with a separated staining agent or dye. Amino acid found in foods are colourless but can be stained using a purple dye called nihydrin. Work out the R f value for the dyed yellow compound at 2.4 cm and 3.6 cm form the solvent origin ? How far did the solvent travel in this example of thin layer chromatography ? Name two solvent that could be used during thin layer chromatography ? C7.16 b 0 2.4 3.6 4.8 (cm) Chromatograph of colourless compounds
Key concepts Look at the photograph and information and answer all the questions: Explain why using two solvent at different angle (90 o ) helps separate all the pigments found in this ink ? What can you say about the red and green pigments ? C7.16 c Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be coloured, especially pigments. This can also be used in secondary or primary colours This method has been largely replaced by thin layer chromatography. Two-way paper chromatography, also called two-dimensional chromatography, involves using two solvents and rotating the paper 90° in between. This is useful for separating complex mixtures of similar compounds, for example, amino acids Two dimensional chromatography Solvent A Solvent B Solvent B Solvent A
Plenary Lesson summary: solvents way inks families Friday 21 October 2011 Companies like Neslte will regularly sample at different stages of turning cow’s milk into powdered baby milk. They need to ensure that the correct amounts of each sugar and amino acid is present to meet the developing baby’s requirements. During the production of baby’s milk from raw material to fished product over 50 different samples are processes to ensure the product is safe and effective. How Science Works: Research into Gas chromatography and how it is sued more complex mixtures when compared to thin layer chromatography. Preparing for the next lesson: Chromatography can also separate out many different compounds in addition to pigments and ____. Two _____ chromatography using different _______ can better separate out similar compound like amino acids of _______ of compounds . C7.16 Decide whether the following statements are true or false : False True 3: Two way chromatograph is done at 180 o to each other ? False True 2: Nihydrin dye will colour purple different amino acids ? False True 1: Ethanol is used as an alternative solvent to water ?