Audio Guides for GCSE and A Level Science
#38 - Condensation Polymers
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about condensation polymers: formed when a diol reacts with a dicarboxylic acid, producing a polyester and water. These polymers are used in fabrics and biodegradable materials like biopolyesters, which decompose quickly, helping to reduce landfill waste.
#37 - Addition Polymers
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about addition polymers: formed by joining monomers with C=C bonds, such as ethene to polyethene. Polymers are non-biodegradable, causing environmental issues like landfill buildup and ocean pollution. Disposing involves burning, which releases harmful gases, or recycling, which is labour-intensive but eco-friendly.
#36 - Esters
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about esters, formed when an alcohol reacts with a carboxylic acid in the presence of an acid catalyst like sulfuric acid. Esters are volatile, have fruity smells, and are used in perfumes and flavorings. For example, ethyl ethanoate, made from ethanol and ethanoic acid, smells faintly of pineapples.
#35 - Organic Compounds Part 2
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about alcohols and carboxylic acids. Alcohols are used as fuels and solvents. They can be oxidized to carboxylic acids, such as ethanoic acid in vinegar. Ethanol is produced industrially from ethene or via fermentation. Carboxylic acids react with metals and carbonates, forming salts.
#34 - Alkanes and Alkenes
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about alkanes and alkenes: alkanes are saturated hydrocarbons with single bonds, while alkenes are unsaturated hydrocarbons with carbon-carbon double bonds. Alkanes undergo substitution reactions with halogens under UV light, while alkenes participate in addition reactions, forming dihaloalkanes. Bromine water distinguishes alkenes by turning colorless, while alkanes remain unchanged.
#33 - Burning Hydrocarbons
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Burning hydrocarbons produces carbon dioxide and water (complete combustion) or carbon monoxide and soot (incomplete combustion). Carbon monoxide is toxic, while nitrogen oxides and sulfur dioxide contribute to acid rain. Cracking converts long-chain hydrocarbons into shorter, useful fuels.
#32 - Crude Oil
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about crude oil: a mixture of hydrocarbons extracted from underground reservoirs. Fractional distillation separates crude oil into fractions based on boiling points, producing fuels like gasoline, diesel, and kerosene. As carbon chain length increases, fractions become darker, more viscous, and have higher boiling points.
#31 - Organic Compounds
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about organic compounds: hydrocarbons are made of carbon and hydrogen only, forming groups like alkanes and alkenes. Represent organic molecules using various formulas, and understand homologous series, functional groups, and isomerism. Naming follows IUPAC rules based on carbon chains and functional groups. Organic reactions include substitution, addition, and combustion, producing compounds like chloromethane and ethanol.
#30 - Dynamic Equilibria
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about dynamic equilibrium: in a closed system, a reversible reaction reaches dynamic equilibrium when the forward and backward reactions occur at the same rate, keeping concentrations constant. Changes in temperature or pressure shift the equilibrium position based on Le Chatelier’s principle, while catalysts speed up the reaction without affecting the equilibrium position.
#29 - Reversible Reactions
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about reversible reactions: these reactions can proceed in both directions, represented by the symbol ⇌. Examples include the heating of ammonium chloride, which decomposes into ammonia and hydrogen chloride, and the dehydration of hydrated copper sulfate, which turns white when heated and reverts to blue upon rehydration.
#28 - Rates of Reaction
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Understand reaction rates: factors like temperature, surface area, concentration, and pressure affect how quickly reactions occur by influencing particle collisions. Catalysts speed up reactions by lowering activation energy without being consumed. Practical examples include changing temperatures, varying concentrations, and using catalysts like manganese oxide to increase reaction rates.
#27 - Bond Energies
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Understand bond energies: energy level diagrams illustrate exothermic and endothermic reactions, showing enthalpy change (ΔH) and activation energy. Breaking bonds requires energy, making it an endothermic process, while forming bonds releases energy, making it exothermic. Calculate ΔH using bond energies: subtract energy released when bonds form from energy required to break bonds.
#26 - Energetics
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about energetics: exothermic reactions release heat, increasing temperature, while endothermic reactions absorb heat, lowering temperature. Calorimetry measures enthalpy change (ΔH) by recording temperature changes during reactions, such as combustion or neutralisation. The heat energy transferred is calculated using the formula Q = mcΔT, helping determine the energy change per gram or mole of a substance.
#25 - Chemical Tests
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about chemical tests: identify gases like hydrogen, oxygen, and carbon dioxide using specific reactions. Flame tests reveal metal ions by color, while tests with sodium hydroxide identify cations like Cu²⁺ and Fe³⁺. Anions like chlorides, sulphates, and carbonates form distinctive precipitates when reacted with specific reagents. Water can be tested chemically with anhydrous copper sulphate or physically by its melting and boiling points.
#24 - Making Salts
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about making salts: soluble salts are prepared by reacting acids with alkalis, often using titration to ensure precise neutralization. Insoluble salts form via precipitation reactions between two soluble reactants, with the resulting precipitate filtered, washed, and dried to obtain a pure sample.
#23 - Acids, Bases and Salts
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Understand acids, bases, and salts: acids are proton donors, and bases are proton acceptors. Acids react with metals, bases, and carbonates to form salts, often releasing gases like hydrogen or carbon dioxide. Solubility rules predict if salts are soluble or form precipitates, aiding in practical salt preparation methods.
#22 - Titrations
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about titrations: a technique used to determine the concentration of an acid or alkali by measuring the volume needed to neutralize it. This process involves using indicators like phenolphthalein, which changes colour at the endpoint, and calculating moles to find unknown concentrations.
#21 - Acids and Alkalis
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about acids and alkalis: acids release hydrogen ions (H⁺), while alkalis release hydroxide ions (OH⁻). Indicators like litmus, phenolphthalein, and methyl orange help distinguish between them. The pH scale classifies solutions from acidic to alkaline, with neutralization reactions forming water when acids and alkalis mix.
#20 - The Uses of Metals
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Understand the uses and extraction of metals. Most metals are extracted from ores, with less reactive metals extracted using carbon reduction and more reactive ones via electrolysis. Metals like aluminium, copper, and iron are used widely due to their properties, such as conductivity and malleability. Alloys, mixtures of metals, are stronger and more resistant than pure metals.
#19 - Metals and the Reactivity Series
A complete set of concise, modern audio guides for Edexcel IGCSE Chemistry (4CH1).
Edexcel IGCSE Chemistry - The Companion Audio Guide
Learn about the reactivity of metals and the reactivity series. Metals react with water and acids, with more reactive metals displacing less reactive ones in redox reactions. Rusting of iron, an oxidation process, can be prevented using barriers, galvanizing or sacrificial protection.