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IGCSE Chemistry

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A series of free IGCSE Chemistry Lessons (Cambridge IGCSE Chemistry).

The nature of matter The states of matter Separating and purifying substances Atoms and molecules The structure of the atom Electron arrangements in atoms Elements and compounds The Periodic Table Trends in groups Trends across a period Chemical bonding in elements and compounds Chemical formulae of elements and compounds Metals, alloys and crystals Chemical reactions Chemical reactions and equations Equations for chemical reactions Types of chemical reaction Redox reactions Electrolysis Electrode reactions Acids, bases and salts What is an acid? Acid and alkali solutions Metal oxides and non-metal oxides Acid reactions in everyday life Alkalis and bases Characteristic reactions of acids Acids and alkalis in chemical analysis Salts Preparing soluble salts Preparing insoluble salts Strong and weak acids and alkalis Quantitative chemistry Chemical analysis and formulae The mole and chemical formulae The mole and chemical equations Calculations involving gases Moles and solution chemistry How far? How fast? Energy changes in chemical reactions Rates of reaction Catalysts Photochemical reactions Reversible reactions and chemical equilibria Patterns and properties of metals The alkali metals Aluminium The transition elements The reactivity of metals Electrical cells and energy Industrial inorganic chemistry The extraction of metals by carbon reduction The extraction of metals by electrolysis Ammonia and fertilisers Sulfur and sulfuric acid The chlor–alkali industry Limestone The economics of the chemical industry Organic chemistry The unique properties of carbon Alkanes Alkenes Hydrocarbon structure and isomerism Chemical reactions of the alkanes Chemical reactions of the alkenes Alcohols The reactions of ethanol Organic acids and esters Petrochemicals and polymers Petroleum Alternative fuels and energy sources Addition polymerisation Condensation polymerisation Chemical analysis and investigation Inorganic analysis Organic analysis Experimental design and investigation Practical examinations The nature of matter
States of Matter and Separation Techniques
The different states of matter, the arrangement and the energy of the particles in solids, liquids and gases.
How to separate various mixtures using techniques such as filtration, distillation and chromatography?
Elements, compounds and mixtures What is meant by an element, a compound and a mixture.How the chemical formula can be used to tell us not only the elements in a compound but also the number of atoms of each element. What is a molecule. Atomic Structure Structure of atoms. Particles in atoms and their relative charges. Why atoms have no overall electrical charge. Atomic number and Mass number How to use the atomic number and mass number to determine the numbers of protons, neutrons and electrons. Electron arrangement in atoms Electron energy levels 3. Elements and Compounds Atoms, Elements and Compounds
The structure of atoms, relative atomic masses and isotopes.
Formulae of elements and compounds, and relative formula masses.
The Periodic Table Group 1 and group 0 Chemistry of Groups 1, 7 and 0
Properties of Group 1: The Alkali Metals, Group 7: The Halogens, Group 0: The Noble Gases
Chemical bonding
How ionic, covalent and metallic bonds are formed?
How to draw dot-and-cross diagrams to represent bonding?
Ionic bonding Covalent bonding Structure of substances
How the properties of substances are related to the their structure and the kind of bonding they have?
Giant ionic structures, simple molecules, giant covalent structure, giant metallic structure.
Trends in the Properties of Elements of Period 3 4. Chemical Reactions Balancing chemical equations 1 Balancing chemical equations 2 Balancing chemical equations 3 Balancing chemical equations 4 Major Types of Chemical Reactions Five major types of chemical reactions: synthesis, decomposition, combustion, single replacement (also called single displacement) and double replacement (also called double displacement). In a synthesis reaction, a compound is made from more simple materials. In a decomposition reaction, a compound breaks down into simpler elements or compounds. In a combustion reaction, a compound (usually with carbon, hydrogen, and sometimes oxygen) combines with oxygen to give carbon dioxide and water. In a single replacement (displacement) reaction, one element that is on its own displaces another element in aqueous solution, kicking it out. In a double replacement (displacement) reaction, the positive and negative ions in two ionic compounds switch places, causing a precipitate to form. Introduction to Oxidation Reduction (Redox) Reactions An oxidation reduction (redox) reaction happens when electrons are transferred between atoms. A loss of electrons is called oxidation, and we say that atom has become oxidized. A gain of electrons is called reduction, and we say that the atoms has become reduced. The two separate parts (oxidation and reduction) of an oxidation reduction (redox) reaction are called half reactions. Two half reactions can be put together to make the whole reaction. Oxidation numbers are numbers that can be written above atoms to show whether they are gaining or losing electrons. Oxidizing Agents and Reducing Agents Oxidizing agents make oxidation happen, and reducing agents make oxidation happen. An oxidizing agent takes electrons from something, allowing it to be oxidized, and a reducing agents gives electrons to something, allowing it to be reduced. You can remember this by noting that the thing that is reduced is the oxidizing agent, and the thing that is oxidized is the reducing agent. We'll then look at some equations and identify the oxidizing and reducing agents. To do this, we have to write oxidation numbers (or oxidation states) for the elements in the equation, and then figure out how electrons are moving, what is being oxidized and what is being reduced. How to Write Net Ionic Equations? How to determine spectator ions and write a net ionic equation? Introducing electrolysis Electrolysis of molten lead bromide Electrolysis of concentrated sodium chloride solution Electrolysis of dilute sodium chloride (inert electrodes) Discussion on selective discharge during electrolysis of aqueous dilute sodium chloride, Electrolysis of aqueous copper(II) sulfate using copper electrodes and its use to refine blister copper by electrolytic refining Electrolysis of aqueous copper sulfate (inert electrodes) Discussion on selective discharge during electrolysis of aqueous copper (II) sulfate Electrolysis of aluminium oxide Electrolysis of concentrated HCl Electrolysis of Dilute Aqueous Sulphuric Acid Introduction to electroplating. Example: copper coating a steel fork Reactivity Series, Tests for Ions, Redox, Displacement
5. Acids, bases and salts Weak and Strong Acids Weak and Strong Bases Differences between alkali and base Characteristics of acids and alkali Acids and Bases: Indicators and pH pH and strengths of Acids and Alkalis Concentration of Acids and Alkalis Properties and uses of acids, bases and alkalis Reaction of acids with bases and alkalis: neutralisation The reaction of acids with carbonates How are acids and alkalis made? How to produce salt by reacting acid with a metal oxide? How to produce salt by reacting acid with a carbonate? Solubility of Salts Solubility of Hydroxides Aluminium and Zinc Hydroxides are amphoteric How to produce salts using precipitate reactions? Acids, Bases and Salts
The nature of acids, alkalis, bases and salts.
What are the different acid reactions which are used to make soluble salts, and the precipitation reactions which are used to make insoluble salts?
6. Quantitative Chemistry Relative Formula Mass How to calculate relative formula mass? It is critically important for our understanding of quantitative chemistry. Beware of a couple of pit-falls. Calculating moles of an Element What is meant by the word "mole" and how to calculate moles of an element. Calculating moles of a Compound How to use the relative formula mass to calculate the number of moles of a compound. Using moles to balance equations Calculating mass of a number of moles How to calculate the mass of a given number of moles? Avogadro's constant 1 How to calculate numbers of molecules and atoms using Avogadro's constant? Avogadro's constant 2 How to calculate numbers of molecules and atoms using Avogadro's constant for a given sample? Reacting masses 1 How to use moles to calculate the masses of reactants or products in chemical reactions? Reacting masses 2 Using moles to calculate the masses of reactants or products in chemical reactions. Limiting reactant What is a limiting reactant? How to work out the mass of the product that we can make in a chemical reaction, even if we are not told which reactant is in excess. Concentration of Solutions How to calculate the concentration of a solution and then the effect of changing the mass of solute and the volume of solution on the concentration. Calculating Percentage Yield 1 How to calculate the percentage yield for a reaction? Why percentage yield is rarely 100% and why students sometimes get this calculation wrong. Calculating Percentage Yield 2 Examples and solutions to show how to calculate the percentage yield for a reaction. Using concentration of solutions How to calculate the concentration of a solution in moles per decimetre3. How to use this to work out the mass of a solute dissolved in a solvent? Basic Calculations
Relative atomic mass, relative formula mass, percentage composition, empirical formula calculations, water of crystallisation.
Calculations involving Moles
The definition of the mole, converting masses, volumes and concentrations to moles, reacting quantity calculations, use of Avogadro's number, and calculations in electrolysis.
Molar Calculations Difference between Emperical Formula and Molecular Formula
7. How far? How fast? Measuring rates of reaction How to measure the rate of a chemical reaction and how to interpret this from a graph. The rate of a reaction depends on the frequency of collisions between the reactant molecules. Concentration and rate of reaction How the concentration of reactants can affect the rate of a chemical reaction? We explore the "disappearing cross" experiment which frequently comes up in the Chemistry exam. Energy changes in reactions How energy changes take place in chemical reactions? What is meant by exothermic and endothermic reactions and look at activation energy and how this is effected by catalysts. Reversible reactions and Le Chatelier's principle What happens when a reversible reaction reaches equilibrium and how we can change the position of the equilibrium using Le Chatelier's principle. Bond energy calculations How we can use bond energies to calculate the energy change for a chemical reaction? Rates of Reaction
Collision theory and how it enables us to predict how different conditions will affect the rate of a reaction.
Experimental methods to determine the rate of a reaction, and the role of catalysts.
Energy Changes and Calorimetry
Endothermic and exothermic reactions, and the process of bond breaking and bond making to calculate how large the energy change during a reaction will be.
Calorimetry: the practical method for measuring the energy changes that accompany reactions.
Equilibrium and Industrial Processes
Reversible reactions, the idea of chemical equilibrium, and how conditions affect the position of equilibrium, before considering the Haber Process and the Contact Process.
How taking control of the equilibrium allows each of these processes to be optimised?
8. Patterns and properties of metals Group 1 (Alkali Metals) and Oxygen Group 1 (Alkali Metals) and Water Identifying metal ions Five flame tests that we use to identify metal ions. How to identify metal ions by precipitation with sodium hydroxide solution. Finally, we look at how to learn the chemical tests. Properties of transition elements and also their reactivity (in comparison to alkali metals). Metal carbonates reacting with acids How different metal carbonates react with acids Four metals you need to know. The definition of the word "ore", which frequently comes up in exams. We then explore four different metals: Iron, copper, aluminium and titanium. Acids reacting with Metals How acids react with metals? We learn what is meant by a salt and why different metals react with acids at differen Acids reacting with Metals 2 Look at the reaction between acids and metals, focusing on the oxidation and reduction reactions taking place. Cells and Batteries How cells and batteries use a chemical reaction to produce electricity? We look at how the reactivities of the metals affect the potential difference produced and we learn the difference between rechargeable and non-rechargeable batteries. Fuel Cells How fuel cells generate electricity, looking specifically at the hydrogen fuel cell? Compare the advantages of hydrogen fuel cells compared with rechargeable batteries. 9. Industrial inorganic chemistry Extraction of iron by carbon reduction How we extract metals from ores. How we extract iron using carbon in a blast furnace. Alloys of iron We can turn pure iron into the alloy steel. We explore why steel is hard and look at low-carbon and high-carbon steel. Finally, we take a look at stainless steel Metal reactivity - Iron, Rusting and Prevention Recycling metals Two really important metals: titanium and aluminium. What makes them so expensive? Three good reasons why we need to recycle metals. Extraction and Uses of Metals
How to extract Aluminum and Iron?
Extraction of Zinc Electrolysis
Properties of Group 1: The Alkali Metals, Group 7: The Halogens, Group 0: The Noble Gases
The vocabulary used in electrolysis and how the process works
How to work out what the products will be when doing electrolysis of ionic compounds when molten, and when in solution?
What are half-equations are also covered?
The chlor-alkali industry as a specific example of the use of electrolysis in industry. Electrolysis of brine.
Contact process How to make sulfuric acid? Equilibrium and Industrial Processes
Reversible reactions, the idea of chemical equilibrium, and how conditions affect the position of equilibrium, before considering the Haber Process (Ammonia) and the Contact Process (Sulfuric Acid).
How taking control of the equilibrium allows each of these processes to be optimised?
Chlor-Alkali Process What is sulfur? Sulfuric Acid properties Limestone to make cement Thermal decomposition of limestone What happens to limestone when we heat it. This process is called thermal decomposition and it is a frequent exam question. Calcium hydroxide and limewater Thermal decomposition of limestone Thermal decomposition of metal carbonates, reactions of metal carbonates with acids, advantages and disadvantages of quarrying, the limestone cycle equations and chemical weathering. 10. Organic chemistry Hydrocarbons Alkanes: methane, ethane and propane and the general formula for alkanes. Properties of hydrocarbons How the length of the carbon chain affects the boiling point, the volatility and the flammability. Unsaturated hydrocarbons Alkenes: the general formula and how we test for unsaturated hydrocarbons using bromine water. Alkanes isomerism Isomers in Alkenes Complete combustion of hydrocarbons Partial combustion of Hydrocarbons What happens when hydrocarbons undergo combustion in the presence of limited oxygen. This is called partial (or incomplete) combustion and it generates the highly toxic gas carbon monoxide, plus water. Pollution from combustion How combustion of hydrocarbons causes pollution? The effects of these pollutants. This includes global dimming, which examiners seem to like but students rarely seem to understand. Reactions of Alkanes 1. Combustion 2. Substitution reaction by a Halogen in the presence of light 3. Cracking an Alkane Addition reactions of Alkenes 1. Addition of Hydrogen - Hydrogenation 2. Addition of water - Hydration 3. Addition of Bromine- Bromination Alcohols The first three alcohols methanol, ethanol and propanol. The structures of these molecules and their reactions. Making ethanol How ethanol is made by two processes: hydration of ethene and fermentation of sugar. Evaluate these two processes to compare the positives and negatives of each. Reactions of ethanol 1. Ethanol as a fuel 2. Oxidation 3. Dehydration 4. Esterification Carboxylic acids How to make ethanoic acid? Esters What are esters? Esterification and the naming of esters. 11. Petrochemicals and polymers Fractional distillation of hydrocarbons How the hydrocarbons in crude oil are separated by the process of fractional distillation. This is critically important as it frequently comes up in exams. Catalytic cracking How to convert long chain alkanes into shorter chain alkanes and alkenes? This is called catalytic cracking. Biofuels How plant materials can be converted into biofuels. We then evaluate the economic, ethical and environmental issues around biofuels. Polymers - Addition Polymerisation How we make polymers from monomers. How to identify the monomer used to make a polymer and be able to work out the repeating unit for a polymer. Compare Addition and Condensation polymerization Condensation Polymerisation - Polyesters Explain the formation of polyesters from dicarboxylic acids and diols. The process is known as condensation polymerisation - forming water molecules together with polyester molecules. Ester link. How to make Polyester (Terylene)? How to make nylon? Issues around using polymers What is meant by the words non-biodegradable We then go on to explore the positive aspects of using polymers and then the negative aspects. What are Biopolymers? How to make carbohydrates? How to make proteins? How to make fats? Hydrolysis of macromolecules Organic Chemistry
How to manufacture Alcohols and Polymers?

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