Chemistry

~10 mins

Chemistry comes from Arabic al-kīmiyā, which derived from Greek khēmeia, possibly meaning "art of transmuting metals." The Arabs preserved and expanded Greek knowledge during Europe's Dark Ages, with scholars like Jabir ibn Hayyan (8th century) developing experimental methods and Al-Razi (9th century) distinguishing between chemical and physical properties. The word entered Latin as alchemia, giving us "alchemy" — the medieval pursuit of turning base metals into gold and finding the elixir of life. Though alchemists failed in these goals, they discovered many chemical processes and substances. Modern chemistry began with Antoine Lavoisier (1743-1794), the "father of modern chemistry," who proved that combustion involves oxygen and established the law of conservation of mass. He also created the first systematic chemical nomenclature. The 19th century brought John Dalton's atomic theory (1803), Dmitri Mendeleev's periodic table (1869), and an understanding that atoms combine in fixed ratios. The 20th century revealed atomic structure through the work of scientists like Ernest Rutherford, Niels Bohr, and Marie Curie, leading to quantum chemistry and our modern understanding of chemical bonding. Today, chemistry studies matter — what it is made of, how it holds together, and how it transforms — connecting the invisible world of atoms and bonds to everyday acts like cooking, cleaning, breathing, fuelling a car, or charging a phone. It explains why salt dissolves but oil floats, why bread rises in an oven, how batteries store energy, and how medicines fit receptors, turning ordinary experience into understandable, predictable change.

1) Atoms are tiny building blocks that make up everything. Each atom has a heavy centre called the nucleus (protons and neutrons) and much lighter electrons that move around it. The number of protons decides the element — one is hydrogen, six is carbon, seventy‑nine is gold — while the outer electrons decide how it reacts. Atoms are mostly empty space, but the forces between electrons make matter feel solid. You meet atoms at work when helium slowly leaks from a balloon because the atoms are so small, a smoke alarm uses a tiny radioactive source to ionise air, and LEDs glow as excited electrons drop back down and release light.

Related: Atom | Atomic nucleus | Electron

2) Elements are pure substances made of just one kind of atom, and the Periodic Table organises them so similar ones sit together. The table runs by increasing proton number, with columns that share behaviour because their outer electrons look alike. Noble gases on the right already have “full” outer shells so they barely react, while alkali metals on the left have one loose outer electron and react quickly, even with water. Neon signs glow without reacting, helium keeps balloons light, and sodium in water fizzes as it makes hydrogen gas and a basic solution. The table even predicts missing pieces, which is how Mendeleev forecast new elements before they were found.

3) Atoms bond because they are more stable together than alone. They can share electrons (covalent bonds) like in water, transfer electrons to make attracting ions (ionic bonds) like in table salt, or pool electrons in a mobile “sea” (metallic bonds) that lets metals conduct electricity and bend. The bond type explains properties you see: diamond is hard because its covalent network locks atoms in place, salt dissolves in water because charged ions are stabilised, and copper wires carry current because electrons move freely through the metal.

4) Molecules are groups of bonded atoms that behave as a unit, and their 3D shape matters as much as which atoms they contain. The same atoms joined differently can give totally different results — ethanol is a liquid you can drink, while its isomer dimethyl ether is a gas. Water’s bent shape makes it polar so it dissolves salts and forms hydrogen bonds. You notice molecular behaviour when fizzy drinks lose CO₂ as pressure drops, perfumes drift because small molecules evaporate easily, and cooking changes flavour as proteins unfold and new molecules form.

5) Chemical reactions rearrange bonds between atoms to make new substances. Breaking bonds needs energy and making bonds gives energy, so the overall change decides whether a reaction gives off heat or needs it. Many reactions need a small push to get started (a match to wood), and catalysts lower that push so things happen faster. You see reactions when baking soda and vinegar fizz to make CO₂, iron rusts faster with salt and water, food is digested by enzymes, and hair dyes work by controlled oxidation.

6) Chemical energy lives in bonds. If a change breaks weaker bonds and makes stronger ones, the “profit” comes out as useful energy. That is how petrol engines push pistons, fires give heat and light, batteries power phones via controlled electron flow, and your muscles run on ATP made from food. The same rule ties everyday energy tech and biology together.

Related: Bond energy | Thermochemistry | Enthalpy

7) Water’s bent shape makes each molecule a tiny magnet, so it forms hydrogen bonds with neighbours. These weak attractions explain why water boils high for its size, stores heat well, and freezes into a lighter, open ice that floats. As a solvent, water surrounds ions so salt “disappears,” while oils huddle together because they are non‑polar. You see this when sweating cools you as water evaporates, coasts have milder weather because oceans buffer heat, insects skate on surface tension, and washing‑up liquid helps water lift grease.

8) Acids give H⁺ and bases take H⁺, and pH measures how acidic something is on a 0–14 scale that jumps by tens each step. Strong acids and bases give almost all their H⁺ or OH⁻, while weak ones give only some. Because protein shapes depend on charge, pH shifts can switch enzymes on or off. Your blood stays near pH 7.4 thanks to buffers that mop up extra acid or base, milk can soften coffee’s bite, antacids calm stomach acid, pool water needs careful pH, and baking uses bicarb plus acid to release CO₂ bubbles.

Related: Acid | Base | pH

9) Carbon is life’s backbone because it makes four bonds and builds chains, rings, and sheets with huge variety. Swap small parts on the carbon frame (functional groups) and you change properties like solubility and acidity. Even mirror‑image forms can behave differently in the body. The same element gives diamond (hard 3D network), graphite (soft sheets that conduct), and graphene (a single ultra‑strong sheet). Oils, plastics, fuels, caffeine, sugars, proteins and DNA are all carbon‑based, which is why organic chemistry feels so close to everyday life.

Related: Carbon | Organic chemistry | Catenation

10) Gas particles are always moving and spread to fill space, bumping into walls to make pressure. Warmer gas moves faster, which raises pressure if the volume cannot change. Gases mix by diffusion, escape faster if they are lighter, and each gas adds its own share of pressure to the total. You experience this when perfume spreads across a room, helium balloons shrink as atoms sneak through rubber, fizzy drinks lose bubbles as pressure drops, your lungs swap oxygen and carbon dioxide across thin membranes, and tyres firm up in summer heat.

Related: Gas | Diffusion | Kinetic theory

11) The Periodic Table is chemistry’s map. As you go across, outer electrons fill up and similar patterns repeat; as you go down, atoms get bigger and outer electrons are easier to remove. That is why alkali metals lose one electron and react, halogens gain one and form salts, and noble gases barely react. The table groups look‑alikes together so you can guess behaviour — sodium and potassium act alike, fluorine and chlorine act alike, and neon and argon are quietly inert.

12) Solids, liquids, and gases reflect a tug‑of‑war between motion and attraction. In solids, particles stay in place and vibrate; in liquids, they stay close but flow; in gases, they fly far apart. Heating tips the balance by loosening attractions so melting and boiling happen. Dry ice skips the liquid stage and turns straight to gas, and the mist you see is cooled water in the air. Water is unusual: ice floats, oceans smooth out weather, and the heat needed to evaporate sweat makes it a powerful cooler. Salt on roads lowers the freezing point so ice is harder to form.

13) Changes of state (melting, boiling, freezing) swap energy with the surroundings but do not make a new substance; only how tightly the particles stick together changes. This hidden energy is latent heat, so temperature plateaus during melting or boiling because the added energy loosens attractions rather than raising temperature, which is also why steam burns more than boiling water when it condenses on skin. Boiling point depends on pressure — high mountains lower it so cooking is slower, while a pressure cooker raises it — and very smooth hot liquids can superheat in a microwave then suddenly boil when disturbed. You see these ideas when chocolate melts in your mouth, alcohol evaporates and cools skin, hot water loosens a tight jar lid as metal expands, and wet clothes dry as evaporation removes heat.

Related: Melting | Boiling | Freezing

14) A solution is a uniform mix where the solute spreads evenly through the solvent; “like dissolves like” because polar water molecules pull apart and wrap polar or ionic substances such as salt and sugar, while non‑polar oils mix with non‑polar make‑up pigments. Warm liquids usually dissolve solids faster but hold less gas, which is why warm cola goes flat sooner. In daily life, tea brews as flavour molecules dissolve, saline eye drops feel gentle because their salt level matches your tears, dish soap bridges water and grease with a water‑loving head and oil‑loving tail, and warm water cleans better because dissolving and diffusion speed up.

Related: Solution | Solubility | Dissolution

15) Concentration is how much substance is packed into a given volume, and higher concentration means more frequent particle bumps, faster reactions and stronger effects; chemists often measure it as molarity (moles per litre), but the idea is simply “more per cup does more.” Strong bleach works while watered‑down bleach does little, spirits feel stronger than beer because the ethanol concentration is higher, IV fluids must match blood saltiness so red blood cells don’t swell or shrivel, and the mixing rule C₁V₁ = C₂V₂ just encodes that halving the volume needs double the strength.

16) Temperature is how fast particles jiggle, so warmer conditions mean more successful collisions and faster reactions; a handy rule is that many reactions go roughly twice as fast for each 10 °C rise, though heat can also denature delicate enzyme shapes so they stop working. You notice this when food spoils faster on the counter than in the fridge, yeast dough rises quicker in a warm kitchen, glow sticks shine brighter but finish sooner in hot water, and medicines last longer when kept in the cold chain.

17) A catalyst is a shortcut that lets a reaction take an easier route with a lower “hill,” so it happens faster without being used up and without changing the final balance of chemicals. You rely on this when laundry enzymes lift stains in cool water, a car’s catalytic converter turns toxic gases into safer ones, and industry uses iron to help make ammonia for fertiliser in the Haber process.

Related: Catalyst | Enzyme | Activation energy

18) Redox is an electron swap: oxidation is loss of electrons and reduction is gain (think “OIL RIG”), and these tiny trades power life and technology. Iron rusts by losing electrons to oxygen, batteries work by separating the loss and the gain so electrons flow through a wire, bleach removes colour by taking electrons from dyes, and antioxidants donate electrons to calm reactive oxygen in cells.

Related: Redox | Oxidation | Reduction

19) Electrolysis uses electricity to split substances that would not split on their own, with reduction (gain of electrons) at the negative electrode and oxidation (loss) at the positive electrode. This underpins making aluminium from ore, electroplating jewellery, producing chlorine and sodium hydroxide from brine, generating hydrogen from water, and re‑charging batteries by pushing electrons the other way.

20) Pressure squeezes particles closer, so gases collide more and the balance of some reactions shifts; if a reaction makes fewer gas molecules, higher pressure tends to push it in that direction, and gases dissolve better in liquids under pressure, which is why bottles fizz when you release the cap. You meet this when pressure cookers raise the boiling point and cook faster, high altitude lowers water’s boiling point and slows cooking, soft drinks are bottled under pressure, and tyres feel firmer on hot days.

21) Equilibrium is a steady truce where forward and backward reactions still happen but at the same speed, so the amounts stay constant; if you push the system it “pushes back” (Le Chatelier), so adding reactant makes more product and heating an exothermic system favours the side that absorbs heat. Unopened cola balances dissolved CO₂ with gas in the headspace until you open it, your blood uses linked equilibria with carbon dioxide to keep pH steady, and factories tune conditions to shift equilibria toward useful products.

22) Organic chemistry is the chemistry of carbon, and because carbon makes four bonds it builds chains, rings, and branches for life and materials. Swapping small pieces on the backbone (functional groups such as alcohols, acids, and amines) changes behaviour: alcohols usually mix with water, acids taste sour and react with bases, and amines can be basic and smell ‘fishy’. The same atoms arranged differently (isomers) can smell or act differently, and mirror‑image forms (chirality) can have different effects — one may be helpful, the other inactive. Shape matters because a drug must fit its target like a glove. Many everyday smells and flavours (vanillin, menthol, limonene) are small organic molecules. Sugars and fats are carbon frameworks for energy and structure, plastics are long carbon chains engineered for strength or flexibility, fuels like petrol and ethanol release energy when burnt, and food colours and medicines are carefully designed organic molecules.

23) Polymers are very long molecules made by joining many small units (monomers) like beads on a string; longer chains and more links between chains make tougher, less flexible materials, while shorter or loosely linked chains feel softer and can flow. Some plastics soften when heated and can be reshaped (thermoplastics), while others set permanently (thermosets). Chains can ‘click’ together across double bonds (addition) or join while releasing small molecules like water (condensation). Starch thickens gravy because long chains tangle in water, rubber bands stretch and spring back thanks to flexible chains and a few cross‑links, nylon and polyester make strong clothing fibres, and soft contact lenses are water‑soaked polymer gels that stay flexible and let oxygen through.

Related: Polymer | Polymerisation | Macromolecule

24) Radioactivity is when an unstable atomic nucleus rearranges itself by spitting out particles or energy until it becomes more stable. The main ‘flavours’ are alpha (a tiny helium nucleus), beta (an electron or positron), and gamma (a burst of high‑energy light). Alpha is stopped by paper or skin, beta by thin metal, while gamma needs thick lead or concrete; distance and time also reduce exposure. Unstable nuclei decay at predictable average rates called half‑lives. This underpins everyday tech: smoke alarms use americium to ionise air, medical scans trace short‑lived isotopes that emit detectable signals, radiotherapy targets tumours, and carbon‑14 dating estimates the age of once‑living things. Background radiation is normal and comes from rocks, cosmic rays, some foods, and medical imaging, with doses managed to stay safe.

25) Chemistry sits between physics and biology, explaining how invisible particles give rise to the stuff and changes we see. Four ideas organise most of it: particles (what is there), energy (can it happen and how much), structure (shape and bonding), and time (how fast). It links scales — quantum rules shape atoms and bonds, thermodynamics says what can happen, kinetics says how fast, and structure explains properties. The same toolkit powers our world: cooking and cleaning, batteries and fuels, medicines and materials, clean water and clean air. Tools such as simple tests and spectra help identify substances and track change. Once you notice reactions, energy, and structure, everyday life becomes readable.

26) Gas laws are simple rules about gases: squeeze a gas and its volume shrinks, warm it and it expands, and if you warm a sealed container the pressure rises. In plain terms, doubling pressure halves volume (if temperature is steady), and heating a balloon makes it bigger. All together this is summarised by PV = nRT for ideal gases, with real gases deviating at high pressure and low temperature. You feel these rules when tyres soften in winter and firm in summer, balloons shrink in the fridge, aerosol cans warn against heat, scuba tanks pack air into small volumes, and weather balloons swell as outside pressure drops.

27) Intermolecular forces are the gentle attractions between molecules that decide boiling points, thickness, surface ‘skin’, and solubility. All molecules have fleeting London forces; polar molecules add dipole–dipole pull; and special hydrogen bonds (with N, O, or F) are stronger still. Water boils much higher than methane because hydrogen bonds are stronger, and honey flows easier when warmed because these forces and chain entanglement loosen. That is why water beads on wax, long oils pour slowly, detergents corral grease into tiny droplets, and non‑stick pans keep food from grabbing the surface.

28) Colligative properties depend on how many solute particles are present, not what they are. Adding particles lowers a liquid’s freezing point, raises its boiling point, reduces its vapour pressure, and creates osmotic pressure across membranes. Salt splits into two particles (Na⁺ and Cl⁻), so it has a bigger effect grain‑for‑grain than sugar. Plants can wilt in salty soil because water is pulled out of roots by osmosis. Everyday examples include road salt melting ice, antifreeze protecting engines across seasons, a pinch of salt in pasta water hardly moving the needle, and reverse‑osmosis purifiers pushing water through a membrane while salts stay behind.

29) Chemical kinetics asks how fast a reaction goes and what controls the speed. Rates usually increase with concentration, temperature, catalysts, stirring, and greater surface area for solids, and many reactions proceed through short‑lived steps. Speed is not the same as final amount (extent) — a fast reaction can still give little if equilibrium lies the other way. You see kinetics in fruit ripening faster in warmth, food and medicines lasting longer in the fridge, glow sticks fading as reactants are used up, and factories tuning temperature, mixing, and catalysts to boost output.

30) Buffers are mixtures that keep pH steady by soaking up added acid or base. They contain a weak acid with its partner base (or the reverse), so if H⁺ is added the base mops it up, and if base is added the acid supplies H⁺. Buffers work best when the pH is close to the acid’s pKa and they have limited capacity — enough acid or base will still shift pH. Nature and daily life rely on this: blood holds near pH 7.4, shampoos and skin products are made gentle, baking balances bicarbonate with acidic ingredients, and swimming pools stay comfortable when buffering is correct.

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