Ukraine 9 клас Chemistry
Chapters: 4
1. Solubility and solutions
Water as a solvent · Solutions and solubility · Composition of solutions · Extraction and water protection
- Intermolecular Forces – Intermolecular forces are weak attractions BETWEEN molecules. From weakest to strongest (for similar-size molecules): London dispersion < dipole–dipole < hydrogen bond. Stronger forces mean higher melting and boiling points, higher viscosity and surface tension, and they decide what dissolves in what.
- Solutions: How Things Dissolve and How Much Can Dissolve – A solution is a uniform mixture of a solute dissolved in a solvent. In water (an aqueous solution) the solute breaks into particles too small to see, so it never settles and passes through filter paper. Concentration tells how much solute is present (mass % = solute ÷ solution × 100). Solubility is the most that can dissolve in 100 g of solvent at a given temperature; beyond it the solution is saturated. Evaporation, crystallisation and distillation separate solutions.
- Mixtures and Their Separation – A mixture has two or more substances mixed without any fixed ratio, and each keeps its own properties. Homogeneous mixtures (solutions) look the same everywhere; heterogeneous ones do not. By particle size we get solutions (< 1 nm), colloids (1–1000 nm) and suspensions (> 1000 nm). Colloids scatter light (Tyndall effect). Concentration tells how much solute is in a solution. We separate mixtures by using a difference in their parts: evaporation, crystallisation, distillation, chromatography, sublimation, centrifugation and coagulation.
- Environmental Chemistry – Environmental chemistry studies the chemicals in air, water and soil, where they come from and what they do. Dry air is about 78% nitrogen, 21% oxygen, 0.9% argon and 0.04% carbon dioxide. Burning fuels adds pollutants such as SO₂, NOₓ, CO and particulates. SO₂ and NO₂ form acids in rain (pH below 5.6). We measure pollution with quantitative tests such as titration, compare the results with standards, and use laws and cleaner technology to reduce harm.
2. Reactions in solutions
Electrolytic dissociation · pH · Ionic reactions
- The pH Scale: How Strong Is an Acid or a Base? – pH is a number from 0 to 14 that tells how acidic or basic a solution is. 7 is neutral, below 7 is acidic and above 7 is basic. Each step down means ten times more H⁺ ions.
- Ionic Equations and Ion-Exchange Reactions – Salts, strong acids and alkalis split into ions in water: they are electrolytes. When two such solutions mix, a reaction happens only if some ions are removed from the solution as a precipitate, a gas or water. A full ionic equation shows every ion; crossing out the ions that do not change (spectator ions) gives the net ionic equation, for example Ag⁺ + Cl⁻ → AgCl↓. Charges and atoms must balance on both sides.
3. Organic substances
Organic compounds and hydrocarbons · Alcohols and organic acids · Compounds of life · Soaps and detergents
- Carbon and Its Compounds: Bonding, Hydrocarbons and Naming – Carbon has 4 outer electrons, so it shares electrons (covalent bonds) instead of gaining or losing them. Because it bonds to itself (catenation) and always makes 4 bonds (tetravalency), it forms millions of compounds: chains, branches and rings, saturated or unsaturated. Compounds with the same functional group form a homologous series that differs by –CH₂–, and IUPAC names are built from the number of carbons + a suffix or prefix for the functional group.
- Chemical Properties of Carbon Compounds, Ethanol and Ethanoic Acid – Carbon compounds burn in oxygen to give CO₂, water, heat and light (combustion); strong oxidising agents turn alcohols into acids (oxidation); unsaturated compounds add hydrogen with a nickel catalyst (addition); saturated compounds swap hydrogen for chlorine in sunlight (substitution). Ethanol reacts with sodium to give hydrogen and dehydrates to ethene; ethanoic acid is a weak acid that makes esters with alcohols and CO₂ with carbonates.
- Biomolecules – A cell is mostly water, plus four big families of carbon compounds: proteins, carbohydrates, lipids and nucleic acids. Grinding tissue in acid separates small molecules (acid-soluble pool) from big ones – proteins, polysaccharides and nucleic acids (acid-insoluble pool). Proteins are chains of amino acids folded into four levels of structure. Polysaccharides are chains of sugars; lipids are fatty acids on glycerol; nucleic acids are chains of nucleotides. Enzymes are protein catalysts that bind a substrate at the active site, lower the activation energy, and are affected by temperature, pH, substrate level and inhibitors.
- Soaps and Detergents: How a Micelle Cleans Oily Dirt – A soap molecule is the sodium or potassium salt of a long-chain fatty acid. Its ionic head loves water and its long hydrocarbon tail loves oil. In water, soap molecules bury their tails in oily dirt and point their heads outward, forming a micelle that is rinsed away. In hard water, Ca²⁺ and Mg²⁺ ions turn soap into insoluble scum; detergents (sulphonate or ammonium salts) do not form scum, so they work in hard water too.
4. Summarising the course
Classification of substances and reactions · Genetic links between substances
- Types of Chemical Reactions – Most reactions fit a few patterns. Combination: A + B → AB. Decomposition: AB → A + B. Displacement: A + BC → AC + B, where the more reactive A pushes out B. Double displacement: AB + CD → AD + CB, where partners swap; if an insoluble solid forms it is a precipitation reaction. Reactions that give out heat are exothermic; those that take in heat are endothermic.