Empirical Tuition

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.

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.

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.

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.

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.

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.

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.

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 compound...

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.

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.

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.

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.

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...

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...

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.

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.

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 color at the endpoint, and calculating moles to find unknown concentrations.

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.

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.

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.

Explore atmospheric gases: air is 78% nitrogen, 21% oxygen, and contains trace gases like argon and carbon dioxide. Combustion and decomposition reactions show oxygen’s role in forming oxides. Carbon dioxide, a greenhouse gas, contributes to climate change by trapping heat in the atmosphere.

Explore Group 7 halogens: fluorine, chlorine, bromine and iodine, which decrease in reactivity down the group. They vary in state and color and participate in displacement reactions, where a more reactive halogen displaces a less reactive one from a compound.

Discover the alkali metals in Group 1, which react vigorously with water to form alkaline solutions. These soft, low-density metals become more reactive down the group due to weaker attraction between their outer electron and the nucleus.

Explore electrolysis, breaking down ionic substances using electricity. Ionic compounds conduct when molten or dissolved, allowing cations to gain electrons at the cathode and anions to lose electrons at the anode.

Understand that metallic bonding involves metals forming lattices of positive ions surrounded by delocalized electrons, explaining their conductivity, malleability, and ductility due to free electrons and sliding ion layers.