Year 10 Chemistry Unit 1 Past Paper 2020/2021 PDF

Name: ___________________ Class: ________ Teacher: _________________ Are there different types of chemical reactions? 2020/2021  Thinking skills and Pers...

Name: ___________________ Class: ________ Teacher: _________________ Are there different types of chemical reactions? 2020/2021  Thinking skills and Personal Capabilities Throughout this booklet you will be using different ‘Thinking skills and Personal Capabilities’. Watch out for the logos below. Now you are: Now you are: Now you are: Now you are: Now you are: 1 Learning Intentions By the end of this unit you should be able to:  Understand what is meant by the term decomposition.  Define the terms oxidation and reduction.  Apply the concept of oxidation and reduction to unfamiliar reactions.  Write a word equation for the thermal decomposition of limestone  List three observations when calcium oxide reacts with water.  Define the terms renewable and non-renewable  List observations to determine the products of a chemical reaction of an acid with metal, carbonate and alkali.  Give the general reactions of an acid with a metal, an alkali (or base) and a carbonate.  Apply the general reactions of acids to unfamiliar reactions.  Define the terms endothermic and exothermic  Explain why reactions are exothermic or endothermic and calculate energy changes  Apply knowledge of the different types of chemical reactions to word equations. New Words and Spellings: By the end of this unit you should know the meaning of the words indicated below and be able to spell all the words listed: Term Definition Combustion Decomposition Endothermic Exothermic Neutralisation Non-renewable Oxidation Reduction Renewable Thermal You should also ensure that you can spell the names of the following: hydrochloric acid, limestone, malachite and sulfuric acid. 2 Investigating Malachite: The term "ore" is generally used for minerals from which metals are extracted. The first step in the extraction of many metals from their ores often involves roasting the ore in air and you will now investigate what happens during this process by roasting a sample of purified malachite (copper carbonate). 1. Describe the sample of the copper carbonate that you have been given. ___________________________________________________________________ Apparatus: Bunsen Burner and mat, boiling tube, test tube holders, safety glasses, test tube with 3cm3 of limewater Method: 1. Put a spatula measure of copper carbonate in a boiling tube and observe the colour. 2. Using a pair of test tube holders, heat the copper carbonate in the blue flame until there is no further colour change 3. Use a pipette to draw up any gas produced during the reaction and bubble this through limewater. 2. What happens to the copper carbonate when it is roasted (heated)? _________________________________________________________________________________________ 3. What happens to the limewater when the gas produced is bubbled into it? __________________________________________________________________________________________ The incomplete diagram below shows how the atoms are joined together in copper carbonate and copper oxide Now you are: O heat + Cu O C Cu O + O 4. What gas do you think is given off while the ore is being roasted? _____________________________________________________________________ 5. Write a word equation for the reaction which has just taken place. Now you are: ___________________________________________________________________ 6. What is the formula for copper carbonate? ____________________________ You will see that the copper carbonate has essentially split up into two new substances, it has not combined with anything. Substances which split up in this way when heated are said to decompose. The type of reaction is known as thermal decomposition (breaking down using heat). 3 Reduction of the Roasted Ore. 6. How might you remove the oxygen from the copper oxide? __________________________________________________________________________________________ __________________________________________________________________________________________ Method: 1. Add some carbon to your boiling tube of black copper oxide 2. Heat strongly in the Bunsen Burner for 5 minutes 7. Write a word equation for this reaction. __________________________________________________________________________________________ 8. What do you see in the boiling tube? __________________________________________________________________________________________ The removal of oxygen from a substance like this is called Reduction. The addition of oxygen to a substance is called Oxidation. If you look carefully at the word equation you have written you will see that one substance is reduced in this reaction while another substance is oxidized. The substance that is being reduced (loses oxygen) is ________________________ The substance that is being oxidised (gains oxygen) is ________________________ This is known as a redox reaction i.e. one where oxidation and reduction occurs simultaneously. Oxidation Reduction ‘removal of oxygen’ RED OX ‘addition of oxygen’ We can use the Reactivity Series to produce further examples of oxidation and reduction. In each case state the substance that has been oxidized and the substance that has been reduced. iron oxide + auminium → aluminium oxide + iron Substance that is being oxidised: Substance that is being reduced: Zinc + Hydrogen oxide → zinc oxide + hydrogen Now you are: Substance that is being oxidised: Substance that is being reduced: Magnesium + carbon dioxide →magnesium oxide + carbon Substance that is being oxidised: Substance that is being reduced : 4  Total = / 15 Homework 1: Investigating Malachite 1. What is the chemical formula for copper carbonate? __________________________________________________________________________________ 2. Describe the colour changes that occur when malachite is heated strongly. ____________________________________________________________________________________ __________________________________________________________________________________ 3. Write a word equation for the thermal decomposition of copper carbonate. __________________________________________________________________________________ 4. What is meant by the term thermal decomposition? ____________________________________________________________________________________ __________________________________________________________________________________ 5. What is observed when carbon reacts with copper oxide? Write a word equation to show the reaction taking place. ____________________________________________________________________________________ ____________________________________________________________________________________ __________________________________________________________________________________ 6. What is the definition of oxidation? __________________________________________________________________________________ 7. What is the definition of reduction? __________________________________________________________________________________ 8. Use the following equations to decide what has been oxidised and what has been reduced. (i) Copper Oxide + Calcium  Calcium Oxide + Copper Substance that is being oxidised = ________________________________ Substance that is being reduced = ________________________________ (ii) Sodium + Zinc Oxide  Sodium Oxide + Zinc Substance that is being oxidised = ________________________________ Substance that is being reduced = ________________________________ 5 Investigating Limestone Limestone is an organic, sedimentary rock. This means it was formed from the remains of tiny shells and micro- skeletons deposited on the sea bed. They were compressed to form solid rock. Limestone is made up of calcium carbonate and decomposes in a similar way to copper (II) carbonate. 1. Use your knowledge of the thermal decomposition of copper (II) carbonate to write a word and a symbol equation for this reaction. Word Equation:_____________________________________________________________________________ Symbols Equation:___________________________________________________________________________ Limestone, however, is much more difficult to decompose than copper carbonate. Method: 1. Put some 2. Given that there is no colour change, how could you prove that a reaction has calcium carbonate occurred? on the edge of a wire gauze _______________________________________________________________________ 2. Heat strongly with the Bunsen _______________________________________________________________________ for 5 – 10 minutes 3. Allow the _______________________________________________________________________ product to cool 4. Place on a watch glass and The solid product is known as quicklime. add a few drops of water 3. What is the chemical name for quicklime? _________________________________ Write down 3 things that happen when water is added to the quicklime. 1. ________________________________________________________________________________________ 2. ________________________________________________________________________________________ 3. ________________________________________________________________________________________ Your teacher will now outline how to turn the product on your watch glass into Limewater. Record how you did this and outline how you tested that the solution was Limewater. __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ This acts as a chemical test for carbon dioxide. Carbon dioxide will turn limewater from colourless to milky. 6 Homework 2: Limestone Research You will now research some aspects of limestone mining and after you have completed your research complete the sections below: 1. What are Lime Kilns? Now you are: ________________________________________________________________________ ________________________________________________________________________ 2. Outline some of the uses of Limestone in the Belfast area: ________________________________________________________________________ ________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 3. What are some of the environmental impacts of having a limestone mine in an area? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 4. Despite the environmental impact limestone mines exist beside towns and cities. What economic benefits does a limestone mine near a town bring? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 5. Can you find some other impacts that large industries, such as mines, have on a community? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 7 Renewable and Non-renewable Resources : In simple terms, a non-renewable resource is one that cannot be replaced in a lifetime once it has been used up. The term applies both to ores (such as malachite and limestone) and sources of energy. Study the table below and working with a partner indicate whether you think a resource is renewable or non-renewable by ticking the appropriate column. Resource Renewable Non-Renewable Coal Wave Power Wind Power Natural Gas Now you are: Solar Power Tidal Power Bauxite Biogas Hydroelectric Power Haematite Oil Malachite Limestone 1. Why are fossil fuels regarded as a non-renewable resource? ________________________________________________________________________________________ 2. What advantage do renewable sources of energy have over non-renewable resources? __________________________________________________________________________________________ __________________________________________________________________________________________ 3. What are the major disadvantages of renewable sources of energy? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 4. What other major source(s) of energy have we failed to mention? __________________________________________________________________________________________ 5. What steps can we take to prevent our sources of metal ores from being exhausted (used up). __________________________________________________________________________________________ 8 Acids – a summary: ACIDS ALKALIS Name Formula Name Formula HCl Sodium hydroxide NaOH H2SO4 Potassium hydroxide KOH HNO3 Ammonia NH3 CH3COOH Sodium carbonate Na2CO3 Indicators are chemical substances that can be used to determine whether a substance is an acid or an alkali. Now you are: Experiment to find the acid, alkaline and neutral colours of some indicators Remember to be careful when handling the chemicals and to wear safety goggles. 1. Take 5cm3 of each sodium hydroxide solution, distilled water and hydrochloric acid and place in separate test-tubes. 2. Add litmus paper to each test tube and record the colour change if any. 3. Repeat for the other two indicators adding 3 drops to each test-tube and recording any colour change. 4. Record your results in the table below and check answers with your teacher. Indicator Acid Neutral Alkaline Red Litmus paper Blue Litmus paper Universal Indicator Phenolphthalein The pH scale Task: (1) Colour the pH scale below the colours you would expect with universal indicator (2) Label the following pH scale to show weak and strong acids and alkalis and a neutral substance. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutralisation: When equal quantities of acid and alkali react together to produce a solution will a pH of 7 9  Total = /20 Homework 3: Energy sources and acids introduction 1. What is the difference between a renewable resource and a non-renewable resource. Give an example of each. __________________________________________________________________________________________ __________________________________________________________________________________________ ________________________________________________________________________________________ 2. Research a renewable resource of your choice and explain how it works. __________________________________________________________________________________________ __________________________________________________________________________________________ ________________________________________________________________________________________ 3. You are given a colourless solution. You suspect it is an acid. Explain how you could prove this. __________________________________________________________________________________________ __________________________________________________________________________________________ _______________________________________________________________________________________ 4. You are given solutions of sulfuric acid and citric acid. Describe a practical you could perform to determine which acid is the strongest. __________________________________________________________________________________________ __________________________________________________________________________________________ ________________________________________________________________________________________ 5. Complete the following table. Substance pH Classification A 9 B Weak acid C Neutral D 1 E 14 6. What advantage does universal indicator have over litmus paper? ________________________________________________________________________________________ 7. You have a sample of hydrochloric acid (a strong acid) and you neutralise it by adding sodium hydroxide. Describe the colour change you would observe. ________________________________________________________________________________________ 10  The Reactions of Acids: Acids are corrosive chemicals that will react with a variety of substances. (i) Acid reacting with Metals: To carry out this reaction, set up the apparatus shown below and drop 2cm of magnesium ribbon into the hydrochloric acid. Magnesium and hydrochloric acid Now you are: Method: 1. Set the apparatus up as shown in the diagram 2. Put 15cm3 of hydrochloric acid into the conical flask 3. Add a strip of magnesium ribbon 4. Collect any gas produced in the test tube 5. Apply a lit splint to the gas in the test tube Write the observations which you make as the reaction occurs. _______________________________________________________________________ _______________________________________________________________________ What happens when you apply the lit splint to the gas? What does this show? _______________________________________________________ _______________________________________________________ Method: 1. Transfer the solution to an evaporating basin and place on a tripod and gauze 2. Heat using a Bunsen Burner until ¾ of the solution has evaporated 3. Leave at the side of the room to crystallise Describe the other product of the reaction: _________________________________________________ This was a salt—in this case the salt is called ______________________________________________ 11 Any metal which is above hydrogen in the reactivity series will react in a similar manner to the reactions above. We can write a general reaction: ACID + METAL → _________ + __________ E.g. hydrochloric acid + magnesium  magnesium chloride + hydrogen Sulfuric acid + magnesium  _____________________ + ________________ (ii) Acid reacting with carbonate: We will illustrate this reaction using the apparatus shown below: Method Observations: 1. Add 5cm3 of sulfuric acid to the boiling ________________________________________ tube 2. Add limewater to the test tube ________________________________________ 3. Add solid copper carbonate to the acid and attach delivery tube straight away ________________________________________ (make sure the delivery tube is underneath the limewater) ________________________________________ What gas is given off as the reaction occurs? _________________________________________________ Method: Describe the other product of the reaction: 1. Transfer the solution to an evaporating basin and place on a tripod and gauze ____________________________________ 2. Heat using a Bunsen Burner until ¾ of the Name the salt: solution has evaporated 3. Leave at the side of the room to crystallise ____________________________________ Water is also one of the products of this reaction but because there is so much in the dilute acid we added originally we cannot illustrate this. 12 Any metal carbonate compound will react in a similar manner to the reactions above. We can write a general reaction: ACID + CARBONATE → _____ + WATER + ________ Hydrochloric acid + sodium carbonate  sodium chloride + water + carbon dioxide Sulfuric acid + copper carbonate  _______________ + ________ + ___________ When reacting an acid with a metal and carbonate, a gas is produced in each reaction. What common observation occurs when a gas is produced in solution? __________________________________________________________________________________________ You have now looked at two chemical tests for gases: Carbon dioxide: limewater will change from colourless to milky/ cloudy Hydrogen: a lit splint will cause a squeaky ‘pop’ Although not produced in the reactions of acids, another common gas is oxygen. Oxygen: a glowing splint will relight Preparing a Salt Describe below how you could prepare a sample of solid copper chloride using copper carbonate and hydrochloric acid. 13 Homework 4: Research Careers in Chemistry Use the internet to find 4 jobs which require chemistry. (The link to the RSC web-site may be useful) and complete the table below. Job Description (what you do in that What other qualifications are job) required or useful? Select one of the jobs you have researched above that you would be interested in finding out more information about. You should now produce a fact file on that job My poster should include: 1. _____________________________ 2. _____________________________ Now you are: 3. _____________________________ 4______________________________ Now you are: 14 (iii) Acid reacting with an alkali Neutralisation occurs when equal quantities of acid and alkali react together. In this experiment you are going to make the salt sodium chloride by neutralising an acid with an alkali. The alkali you will use is sodium hydroxide. 1. Which acid will you use? ____________________ Method: 1. Measure 10 cm3 of 1M sodium hydroxide into the conical flask and add methyl orange. 2. Add the acid slowly until the solution becomes neutral. 3. To remove the indicator, add a spatula of activated charcoal and swirl carefully. 4. To remove the activated charcoal, simply filter. 5. Transfer the pure salt solution to an evaporating basin and partially evaporate. 6. Leave aside to crystallise. 2. Was there any sign of a gas being produced as you mixed the acid and the alkali? _______ because ___________________________________________________________________________ 3. Why must you add the acid slowly? __________________________________________________________________________________________ 4. Draw a labelled diagram for: (a) the filtering stage (b) the crystallization stage 5. Write a word equation for the reaction: _________________________________________________________________________________________ This experiment illustrates the general type of reaction which occurs when an alkali reacts with an acid. ACID + METAL HYDROXIDE → __________ + WATER Note: There is only a small difference between a substance called an alkali and a bigger group of substances called bases so we also write ACID + METAL OXIDE → __________ + WATER Alkalis are examples of soluble bases, so are often found in solution. Bases are insoluble so are often found as solids. E.g. hydrochloric acid + sodium hydroxide  sodium chloride + water Sulfuric acid + potassium hydroxide  ________________ + __________ 15 Summary of the Reactions of Acids: There are two pieces of information you need to remember: (1) The general reactions of acids: Acid + Metal hydroxide  Acid + Metal oxide  Now you are: Acid + Carbonate  Acid + Metal  (2) The type of salt each acid produces: Salts are the compounds produced when acids react with metals, bases or carbonates. The name of the salt depends on the metal present (this forms the first part of the name of the salt) and acid used (this forms the second part of the name of the salt) Sulfuric acid produces salts called sulfate Hydrochloric acid produces salts called chloride Nitric acid produces salts called nitrate Ethanoic acid produces salts called ethanoate Homework 5: Learning Learn the general equations above for a test next lesson Using the rules above, name the salts that would be produced. 1. Iron and hydrochloric acid = ____________________________ 2. Copper oxide and nitric acid = __________________________ 3. Aluminium and nitric acid = _________________________ 4. Sodium hydroxide and ethanoic acid = _____________________ 5. Calcium carbonate and hydrochloric acid = __________________ 6. Zinc oxide and sulfuric acid = _____________________ 7. Magnesium oxide and nitric acid + ______________________ 8. Lithium and ethanoic acid = _______________________ 16 Use the general equations on the previous page to complete the following word equations. Think about what type of substances are reacting together. E.g. Calcium Carbonate + Nitric acid  ______________________ + Naming the salt: the metal present is _________ + _____________ calcium, so this is the first part. The acid used is This is a carbonate so nitric acid, this should react to form a salt, means the second water and carbon dioxide. part is nitrate In all examples, think about the name of the salt produced. Then identify what type of substance is reacting with the acid. Finally identify what else is being produced by the reaction. 1. Sodium + Sulfuric  Now you are: Hydroxide Acid 2. Copper + Nitric  Carbonate Acid 3. Magnesium + Ethanoic  Acid 4. Sodium + Hydrochloric  Carbonate Acid 5. Copper + Sulfuric  Hydroxide Acid 6. Zinc + Nitric  Acid 7. Lithium + Ethanoic  Hydroxide Acid 8. Aluminium + Sulfuric  Acid 9. Iron + Hydrochloric  Oxide Acid 10. Calcium + Nitric  Carbonate Acid 17 Additional Practice Complete the following word equations: Sodium hydroxide + nitric acid  __________________ + _______________ Copper carbonate + _______________  copper chloride + ____________ + ________________ Calcium oxide + __________________  calcium sulfate + ______________ ____________ + __________________  zinc chloride + ___________________ ______________________ + ___________________  potassium nitrate + water ______________________ + ___________________  iron sulfate + water + carbon dioxide What reactants could you use to produce the following salts: (a) Sodium chloride ____________________ acid with __________________________ Or __________________________ Or __________________________ (b) copper ethanoate ____________________ acid with __________________________ Or __________________________ Or __________________________ (c) aluminium sulfate ____________________ acid with __________________________ Or __________________________ Or __________________________ Decide on a way to produce the following salts and write a word equation to show this. (1) potassium ethanoate _________________________________________________________________________________________ (2) rubidium nitrate __________________________________________________________________________________________ (3) barium sulfate __________________________________________________________________________________________ 18 Exothermic and Endothermic Reactions: Chemical reactions that give out heat to the surroundings are called Exothermic reactions (EXIT = Way Out). Chemical reactions that take in heat are called Endothermic reactions. In each of the experiments that you will carry out the reactions will take place in the solution. As a result the reaction will give heat to the solution or take heat away from the solution. This will cause the temperature of the solution to either rise or fall. Experiment: investigating endothermic and exothermic reactions Apparatus: Chemicals: Safety:  25cm3 measuring  Sodium hydroxide  All solutions cylinder solution are corrosive  Polystyrene cup in a  Hydrochloric acid  Safety beaker surrounded by solution glasses must cotton wool  Solid sodium hydrogen be worn  Thermometer carbonate  Care with  Weighing boat  Solid magnesium thermometer  Spatula  Powdered zinc  General lab  Copper (II) Sulfate safety solution Complete the four experiments and record results in the table provided. Experiment 1 Observations: 1) Using the measuring cylinder add 20cm3 of sodium hydroxide to the polystyrene cup supported in a beaker with cotton wool 2) Record the temperature of the sodium hydroxide 3) Using the measuring cylinder, measure 20cm3 of hydrochloric acid and add to the polystyrene cup Now you are: 4) Stir gently with the thermometer and record the highest temperature reached Experiment 2 1) Using the measuring cylinder add 20cm3 of hydrochloric acid to the polystyrene cup supported in a Observations: beaker with cotton wool 2) Record the temperature of the hydrochloric acid 3) Add one spatula measure of sodium hydrogen carbonate to the acid 4) Stir gently with the thermometer and record the highest temperature reached 19  Experiment 3 Observations: 1) Using the measuring cylinder add 20cm3 of hydrochloric acid to the polystyrene cup supported in a beaker with cotton wool 2) Record the temperature of the hydrochloric acid 3) Add 2cm of magnesium ribbon 4) Stir gently with the thermometer and record the highest temperature reached Experiment 4 Observations: 1) Using the measuring cylinder add 20cm3 of copper (II) sulfate to the polystyrene cup supported in a beaker with cotton wool 2) Record the temperature of the copper (II) sulfate 3) Add a small spatula of zinc powder 4) Stir gently with the thermometer and record the highest temperature reached Results: Initial Final Temperature Temperature Endothermic or Temperature (°C) (°C) Change (°C) Exothermic? Exp. 1 Exp. 2 Exp. 3 Exp. 4 Work with you partner to write word equations that show what is occurring in each of the experiments: Exp. 1 ____________________________________________________________________________________ Exp. 2 ____________________________________________________________________________________ Exp. 3 ____________________________________________________________________________________ Exp. 4 ____________________________________________________________________________________ 20 Why Reactions are Exothermic or Endothermic When substances react together bonds are broken in the reactants and then formed again when the products are produced. Energy is required to actually break to the bond holding the atoms together. Energy is given out when bonds are formed between atoms making the products. It depends on the balance between these values if it is exothermic or endothermic. For exothermic reactions, energy is released to the surroundings. This means that the energy given out when forming the bonds must be greater than the energy taken in when breaking the bonds. For endothermic reactions, energy is taken in from the surroundings. This means that the energy taken in when breaking the bonds must be greater than the energy released when forming new bonds. When answering questions explaining why a reaction is exothermic or endothermic, it is important to name what bonds are being broken and formed. Example - Hydrogen and oxygen react together to form water in an exothermic reaction. Bonds are broken in the molecules of hydrogen and oxygen. This requires energy. Bonds are formed when water is made. This gives out energy. More energy is given out due to bond formation than is used up due to bond breaking, so the reaction is exothermic. Try the following yourself. 1. Explain, in terms of bond formation and breaking, why the reaction between hydrochloric acid and magnesium oxide is exothermic. Magnesium oxide + hydrochloric acid  magnesium chloride + water __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 21 2. Explain, in terms of bond formation and breaking, why photosynthesis is endothermic. Carbon dioxide + water  glucose + oxygen __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ Working Out Energy Changes Scientists know how much energy it takes to break a specific bond (the same amount of energy is released when the bond is formed). E.g. to break a C-H bond requires 413 kJ of energy, but when a C-H bond is formed it releases 413 kJ of energy. To work it out mathematically, you must list all the bonds that are broken and formed. The diagram below shows the combustion of methane. CH4 + 2O2 CO2 + 2H2O Bond C–H C–C O–H C=O O=O Bond energy / kJ 413 347 464 805 498 Bonds broken Bonds formed 4 x C-H 2 x C=O 2 x O=O 4 x O-H Total = total = Energy change = bonds broken – bonds formed = Exothermic reactions will have a negative energy change value. Endothermic reactions will have a positive energy change value, 22 Use the bond energy values in the table below to answer the following questions. Set them out the same way as the example above. Bond Mean bond enthalpy (kJ mol–1) Cl–Cl 243 Cl–H 432 H–H 436 C–H 413 O=O 498 O–H 464 1. Hydrogen + chlorine  hydrogen chloride H–H Cl – Cl H – Cl H – Cl Bonds broken Bonds formed Energy change = bonds broken – bonds formed = This reaction is _______________________ because ______________________________________________ __________________________________________________________________________________________ 2. Methane + oxygen  carbon dioxide + water Bonds broken Bonds formed Energy change = bonds broken – bonds formed = This reaction is _______________________ because ______________________________________________ __________________________________________________________________________________________ 23 Summary - Types of Chemical Reactions: Type of Reaction Explanation Example Thermal decomposition Neutralisation Endothermic Exothermic Oxidation Reduction Combustion When a substance is burnt in air (oxygen) Petrol, ethanol Each of the five word-equations below represents a different chemical reaction. Now you are: A. calcium carbonate → calcium oxide + carbon dioxide B. copper oxide + sulfuric acid → copper sulfate + water C. sulfur + oxygen → sulfur dioxide D. copper oxide + hydrogen → copper + water E. potassium hydroxide + nitric acid—>potassium nitrate + water Using the appropriate letters in each case, answer the following questions. (i) In which reaction is the first-named substance in the equation being oxidised? _____ (ii) In which reaction is the first-named substance in the equation being reduced? _____ (iii) Which reaction shows thermal decomposition? _____ (iv) In which two reactions does neutralisation occur? _____ and _____ 24 Use the self-assessment to guide your revision. Self-Assessment Confident that I I need some understand this more work to Not completely become confident on I can: confident on this. this. Understand what is meant by the term decomposition. Define the terms oxidation and reduction. Apply the concept of oxidation and reduction to unfamiliar reactions. Write a word equation for the decomposition of limestone (calcium carbonate). List three observations when calcium oxide reacts with water. Define the terms renewable and non-renewable List observations to determine the products of a chemical reaction of an acid with metal, carbonate and alkali. Give the general reactions of an acid with a metal, an alkali (or base) and a carbonate. Apply the general reactions of acids to unfamiliar reactions. Define the terms endothermic and exothermic Apply knowledge of the different types of chemical reactions to word equations. 25 Evaluation: Formal homework score: End of topic test score: Aspects of the unit that I understand: Aspects of the unit that require more work to fully understand: One the skills diagram below, list any areas of this unit where you have developed any of these skills. 26