Ch 5 Chemical reactions.pdf

Year 10 Chemistry 2023 Chemical Reactions  Describe chemical reactions using chemical formulae Write correctly balanced chemical equations Describe precipitation reactions and predict what substances will form a...

Year 10 Chemistry 2023 Chemical Reactions  Describe chemical reactions using chemical formulae Write correctly balanced chemical equations Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Recognise and interpret an MSDS and a risk assessment Chemical reactions Understand the need to use laboratory chemicals safely and responsibly Know the dangers associated with each of the classes and subclasses of substances classified as involve rearranging dangerous goods Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, atoms to form new combination and neutralisation reactions substances; during a Describe the transfer of electrons to and from different atoms in redox reactions chemical reaction Know the difference between oxidation and reduction in redox reactions mass is not created Know examples of a range of redox reactions Understand fractional distillation is used in the refining of crude oil for use in combustion reactions or destroyed Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated Know some examples of the use of biofuels as alternatives to fossil fuels Describe the effect of temperature, surface area of solid reactants and concentration of reactants on the rate of chemical reactions Describe the role of catalysts in chemical reactions Investigate examples of the use of naturally occurring catalysts in the human body  Chemical reactions COMPLETE THE FOLLOWING 5.1 Topic 5 pre-test Q 1-15 online 5.1.2: Think about chemical reactions Q 1-6 5.1.3 Science enquiry: chemical reactions Q 1-3 Describe chemical reactions using chemical formulae  5.2 Chemical formulae and equations HOW TO BALANCE CHEMICAL EQUATIONS Write correctly balanced chemical equations  HOW TO BALANCE CHEMICAL EQUATIONS Write correctly balanced chemical equations Write correctly balanced chemical equations Write correctly balanced chemical equations Write correctly balanced chemical equations  Balancing practice questions: Step 1: Word equation Step 2: Replace words with formulae CO + O2 → CO2 Element Reactants Products Step 3: Count number of atoms for products and C 1 1 reactants O 3 2 Step 4: Place numbers 2CO + O2 → 2CO2 (called coefficients) in Element Reactants Products front of reactants and products so there is the C 2 2 same number on each O 4 4 side of the arrow. Step 5: Include states 2CO(g) + O2(g)→ 2CO2(g) Write correctly balanced chemical equations Balancing practice questions: Step 1: Word equation Step 2: Replace words NaOH + HCl → NaCl + H2O with formulae Element Reactants Products Step 3: Count number of atoms for products and Na 1 1 reactants O 1 1 H 2 2 Cl 1 1 Step 4: Place numbers NaOH + HCl → NaCl + H2O (called coefficients) in front of reactants and Element Reactants Products products so there is the Na 1 1 same number on each O 1 1 side of the arrow. H 2 2 Cl 1 1 Step 5: Include states NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)  Balancing practice questions: Step 1: Word equation Step 2: Replace words with formulae Hg + O2 → HgO Step 3: Count number of Element Reactants Products atoms for products and Hg 1 1 reactants O 2 1 Step 4: Place numbers 2Hg + O2 → 2HgO (called coefficients) in front of reactants and Element Reactants Products products so there is the Hg 2 2 same number on each O 2 2 side of the arrow. Step 5: Include states 2Hg (l) + O2 (g) → 2HgO (s) Write correctly balanced chemical equations  Balancing practice questions: Mg (s) + 2HCl (aq) → H2 (g) + MgCl2 (aq) 2Na (s) + 2H2O (l) → H2 (g) + 2NaOH (aq) CuSO4 (aq) + 2NaOH (aq) → Cu(OH)2 (s) + Na2SO4 (aq) Write correctly balanced chemical equations Write correctly balanced chemical equations Write correctly balanced chemical equations  Final summary of how to balance an equation Write correctly balanced chemical equations Write correctly balanced chemical equations 5.2 Chemical formulae and equations Activities 5.2 Exercise: Remember Q 1-4 5.2 Exercise: Apply Q 5-7 5.2 Exercise: Evaluate Q8 Worksheet (in booklet): Chemical equations, pages 29-30 Balancing chemical equations, page 31 A world of reactions, pages 32-33  5.3 Precipitation reactions Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility  Precipitation reactions In this example, the solute particles make stronger bonds with each other than with water. These solute Soluble Solutes particles are "insoluble" in water (ie they will not dissolve) In this solution the solute particles make stronger bonds with the water than they do with each other. These solute particles are "soluble" Insoluble Solutes in water (ie they dissolve) Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility  The SNAPE rule Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility  Writing Precipitation Reactions: 1. copper sulfate + sodium carbonate Full equation CuSO4 (aq) + Na2CO3 (aq) → CuCO3 (s) + Na2SO4 (aq) 2. barium chloride + potassium chromate BaCl2 (aq) + K2CrO4 (aq) → BaCrO4 (s) + 2KCl(aq) Pb(NO3)2 (aq) + Na2CO3 (aq) → PbCO3 (s) + 2NaNO3 (aq) Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility Describe precipitation reactions and predict what substances will form a precipitate using the rules of solubility 5.3 Precipitation reactions activities 5.3 Exercise: Remember and understand Q 1-3 5.3 Exercise: Apply and analyse Q 4-5 5.3 Exercise: Evaluate Q 6-7 Investigation 5.1 Will it precipitate? (in booklet) Pages 45-47 Worksheet (in booklet) 5.4 Precipitation pages 34-35 STILE: reaction types 2.1 Precipitation reactions 5.4 Dangerous goods and hazardous substances Dangerous goods These are chemicals in the dangerous goods group which could be dangerous to people, property or the environment. Dangerous goods must be identified with the appropriate dangerous goods sign on their labels. Hazardous goods Chemicals in the hazardous substances group are those that have an effect on human health. Hazardous substances are identified on their labels by a signal word providing a warning about the substance, or the word ‘Hazardous’ printed in red. Know the dangers associated with each of the classes and subclasses of substances classified as dangerous goods Know the dangers associated with each of the classes and subclasses of substances classified as dangerous goods  Material safety data sheet (MSDS) All chemical suppliers need to has an msds available for the chemical they produce The form of a risk assessment varies from school to school, but will always contain: a summary of the experiment a list of the risks and safety precautions for each chemical information about whether the chemical is classified as a hazardous substance or dangerous good a list of protective measures to be taken. These might include the use of a fume hood and/or the wearing of safety glasses or other protective items. first aid information. Recognise and interpret an MSDS and a risk assessment  Mini msds example Recognise and interpret an MSDS and a risk assessment Recognise and interpret an MSDS and a risk assessment  Risk assessment A risk assessment identifies the potential hazards of an experiment and gives protective measures to minimise the risk. See next slide for an example risk assessment Recognise and interpret an MSDS and a risk assessment Recognise and interpret an MSDS and a risk assessment  Understand the need to use laboratory chemicals safely and responsibly  5.4 Dangerous goods and hazardous substances activities 5.4 Exercise: Remember Q 1-5 5.4 Exercise: Apply Q 6-9 5.4 Exercise: Evaluate Q 10-12 Worksheet (in booklet) : Understanding chemical hazards, pages 36-38  5.5 Types of chemical reactions Dry Corrosion (no water, just oxygen, this is a redox reaction) 1. Solid zinc 2. Oxygen 3. The zinc has comes in contact pinches zinc's been turned into with oxygen. delocalised brittle zinc oxide (a electrons. salt!). Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Dry Corrosion Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions Preventing corrosion galvanised surface barrier layer Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Displacement reactions Displacement reactions are reactions where an element displaces another element from a compound. The reactions of metals with acids are examples of this. In the reaction below Copper (Cu) is displaced by silver (Ag) Cu (s) + 2AgNO3(aq) → Cu(NO3)2 (aq) + 2Ag (s) Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Displacement reactions In these reactions hydrocarbons (molecules made of carbon and hydrogen) react with oxygen in the atmosphere and produce carbon dioxide and water. Hydrocarbons include petrol, methane (gas in the science laboratory) and propane (barbeque gas) CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g) Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Decomposition reactions A single compound breaks down into two or more simpler products CaCO3 (s) → CaO (s) + CO2 (g) Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Combination reactions When two elements combine in chemical reactions to form a compound. 2Mg (s) + O2 (g) → 2MgO (s) Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions Types of chemical reactions (3min)  Redox reactions Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  Chemistry is all about electrons. Substances bond together by swapping or sharing electrons. Substances are attracted to each other via electrostatic attractions (delta + and delta -) caused by electron distributions within molecules. Describe the transfer of electrons to and from different atoms in redox reactions  Redox reactions Note that oxidation and reduction are processes. Reduction is the process whereby electrons are added to a substance. Oxidation is the process whereby electrons are removed from a substance. Remember OIL RIG Oxidation is the loss of electrons Reduction is the gain of electrons Know the difference between oxidation and reduction in redox reactions  The Dry Corrosion of Aluminium is an example of a REDOX reaction 1. Solid aluminium comes in 2. Oxygen pinches aluminium‘s 3. The aluminium has contact with oxygen. delocalised electrons. been turned into brittle aluminium oxide (a salt!). Al loses electrons, O2 gains electrons, thus thus aluminium is oxygen is reduced oxidised Know examples of a range of 2Al3+ + 3O2- → Al2O3 redox reactions  Displacement of silver (oxidation) (loss of electrons) (reduction) (gain of electrons) overall Cu (s) + 2Ag+(aq) → Cu2+ (aq) + 2Ag (s) equation? Know examples of a range of redox reactions  Combustion of methane CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g) In combustion reactions oxygen always gains the electrons so it always under goes reduction or is reduced. The fuel which in this case loses electrons and hence undergoes oxidation or is oxidised. Combination reactions 2Mg (s) + O2 (g) → 2MgO (s) Magnesium loses electrons as it becomes a 2+ ion, therefore it undergoes oxidation. The oxygen gains electrons as it becomes a 2- ion, therefore it undergoes reduction Know the characteristics of precipitation, corrosion, displacement, combustion, decomposition, combination and neutralisation reactions  reduction Know examples of a range of oxidation redox reactions Electron exchange: Watch to 2.47min 5.5 Types of chemical reaction activities 5.5 Exercise: Remember Q 1-5 5.5 Exercise: Apply Q 6-9 5.5 Exercise: Evaluate Q 10-11a Investigation 5.2 Decomposing zinc carbonate (in booklet) pages 48-50 Worksheets (in booklet) : Metal displacement, pages 39-40 Corrosion and combustion, pages 41-42  5.8 Fuels and hydrocarbons Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated  Fossil fuels are a very indirect form of solar energy All organic matter can then transform to fossil fuels over a very long time Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated  methane + oxygen ⟶ carbon dioxide + water vapour CH4(g) + 2O2(g) ⟶ CO2(g) + 2H2O(g) Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated Understand the advantages and carbon + oxygen ⟶ carbon dioxide disadvantages of the use of fossil fuels and their alternatives for the supply of energy is C(s) + O2(g) ⟶ CO2(g) often debated  Steps in the Formation of Coal A long, long, long, long time! Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated  Liquid fuel Understand the advantages and disadvantages of the use of fossil fuels and their alternatives for the supply of energy is often debated Crude oil as a source of raw materials Crude oil is no use as a fuel but it contains many of the compounds that are required The oil is separated into several fractions, each containing a number of hydrocarbons that have similar boiling points Understand fractional distillation is used in the refining of crude oil for use in combustion reactions  Alternatives to fossil fuels What are Biochemical Fuels (Biofuels)? Biochemical fuels (biofuels) are fuels derived from plant materials such as grains, sugarcane, vegetable waste, or vegetable oils. The two main types are ethanol and biodiesel. ethanol biodiesel ester H O H O C17H34O2 H C H C C H H C O H H H C2H5OH Know some examples of the use of biofuels as alternatives to fossil fuels  What are the advantages of using biochemical fuels? Biofuels are also a renewable resource because we can keep re-growing the plant materials (aka biomass) used to make these fuels. They can be replenished at the rate they are used. Know some examples of the use of biofuels as alternatives to fossil fuels  Biogas (approximately) Know some examples of the use of biofuels as alternatives to fossil fuels Biogas  Bioethanol E10 fuel is comprised of 10% ethanol and 90% petrol Know some examples of the use of biofuels as alternatives to fossil fuels 5.8 Fuels and hydrocarbons activities 5.8 Exercise: Remember Q 1-6 5.8 Exercise: Apply Q 7-11 5.8 Exercise: Evaluate Q13-15  5.10 Rates of reaction Chemical Reactions Reactants Products For a chemical reaction to The new substances occur, the reactants must have new bonds Describe the effect of collide with enough energy so between the atoms. temperature, surface area that their bonds break. The of solid reactants and concentration of reactants broken pieces can reform into on the rate of chemical new substances. reactions  Rates of reaction The overall rate of a chemical reaction depends on the number of successful reactant collisions. Describe the effect of It isn't enough for reactants just to collide. They must collide with temperature, surface area of sufficient activation energy and correct orientation too! solid reactants and concentration of reactants on the rate of chemical reactions  Rates of reaction Describe the effect of temperature, surface area of solid reactants and concentration of reactants on the rate of chemical reactions  Fast and Slow Reactions The rate of a reaction is a measure of how quickly a chemical reaction occurs. Chemical Reactions can be sped up by: Heating Pressurising Using Catalysts Powdering Describe the effect of temperature, surface area of solid reactants and concentration of reactants on the Adding more Shining Light rate of chemical reactions reactants on reactants  Speeding Up Reactions 1. Increase the concentration or pressure Not many red and blue particles are in the container. Their chances of colliding are very low. slow reaction All the red and blue particles have reacted because there is a bigger chance of them colliding with each other. The frequency of collisions increases and so more Describe the effect of fast successful collisions occur in temperature, surface area of solid reactants and reaction a given time. concentration of reactants on the rate of chemical reactions  Speeding Up Reactions 2. Increase the surface area Not many red and blue particles have reacted because they are too clumped together. slow reaction All the red and blue particles have reacted because they started off in little pieces. The consequence of the greater number of exposed particles, fast the frequency of collisions between these particles and the other reactant reaction particles increases, and so the reaction Describe the effect of temperature, occurs more rapidly surface area of solid reactants and concentration of reactants on the rate of chemical reactions  Speeding Up Reactions 3. Increase the temperature Cold Conditions Red and blue particles don't collide very often because they are moving so slowly! slow reaction Hot Conditions Red and blue particles have a much better chance of colliding because they are fast moving so fast! Describe the effect of temperature, surface area of reaction solid reactants and concentration of reactants on the rate of chemical reactions  Speeding Up Reactions 4. Use a catalyst Without any catalyst particles, red and blue particles will only collide with each other by sheer chance. Catalyst particles 'catch' both red and blue particles. The catalyst particles hold the red and blue particles together and help them to react. It results in a greater proportion of collisions are ‘successful’. Thus the reaction rate is increased. Describe the role of catalysts in chemical reactions  Catalysed Reactions Catalysts work by allowing reactant substances to adsorb onto their surface. Adsorption distorts bonds in reactant molecules, or may even break them completely. This allows the reaction to proceed more easily. Describe the role of catalysts in chemical reactions  Common Catalysts (many discovered by trial and error!) Describe the role of catalysts in chemical reactions  2 General Types of Catalysts: Homogeneous Catalysts (in the same state as the reactants) (eg gaseous Cl from CFCs catalysing the destruction of ozone molecules) Heterogeneous Catalysts (in a different state to the reactants) (eg gaseous solid platinum and rhodium to clean up car exhaust gases) (easy to separate reactants and products) NOTE: Catalysts are not consumed in a reaction. Describe the role of catalysts in They do not appear as reactants in the reaction either. chemical reactions  The only useful part of a catalyst is it's surface. The surface of a catalyst is where the catalysed reactions occur. Powdered or sponge-like solid catalysts are the most effective types because they have such large surface area to volume ratios. more effective powdered catalyst mildly effective catalyst more effective sponge catalyst Describe the role of catalysts in chemical reactions  Enzyme Action (biological catalysts) Investigate examples of the use of naturally occurring catalysts in the human body  5.10 Rates of reaction activities 5.10 Exercise: Remember Q 1-4 5.10 Exercise: Apply Q6-7 5.10 Exercise: Evaluate Q10 Factors affecting rates of reaction poster investigation (separate document) Worksheet (In booklet): Speeding up reactions, pages 43-44 STILE: Reaction types 4.1 Rates of reaction 4.2 Temp and rates 4.3 surface area and rates 4.4 Concentration and rates Revision activities eWorkbook revision sheets for chapters 4 and 5