627 articles
All articles — Page 12
Every article in the chemistry library, newest first.
Hormones as Chemical Messengers
How hormones work chemically: the three structural classes (peptides, steroids and amino acid derivatives), why solubility decides where the receptor is, signal amplification and second messengers, feedback control, and examples from insulin to thyroxine.
Acids and Bases in Your Home
A room-by-room tour of the acids and bases in an ordinary home: kitchen, bathroom, laundry, garden and medicine cabinet, with their chemical names, approximate pH, what they do and how to use them safely.
How Antibiotics Work: Penicillin and Beyond
The chemistry of antibiotics: selective toxicity, the five main bacterial targets (cell walls, ribosomes, DNA copying, folate synthesis and membranes), how β-lactams like penicillin work, why antibiotics don't kill viruses, and the chemistry of resistance.
How Many Atoms Are in the Observable Universe?
The famous answer is about 10⁸⁰ atoms. Here is how scientists estimate it, step by step, using stars and galaxies and then cosmic density, plus how that number compares with atoms in the Earth, your body and a drop of water.
Can We See Atoms? Electron Microscopes and Scanning Tunnelling Microscopy
Atoms are far smaller than light waves, so no ordinary microscope can show them. Here is how electron microscopes, scanning tunnelling microscopes and atomic force microscopes finally let us image, and even move, single atoms.
How Small Is an Atom? Scale, Size and Mind-Bending Comparisons
Just how tiny atoms are, with real numbers and comparisons: atomic radii in picometres, how many atoms fit across a hair, the mass of a single atom, the size of the nucleus, the number of atoms in a drop of water or a human body, and how scientists measure something so small.
The Chemistry of mRNA Vaccines
How mRNA vaccines work at the molecular level: the mRNA and its cap, tail and modified nucleosides, why unmodified RNA triggers inflammation, the four lipids in lipid nanoparticles and how they deliver RNA, why the vaccines need cold storage, and what happens to the mRNA afterwards.
HPLC Explained
How high-performance liquid chromatography works: pumps, columns, reversed-phase separation, detectors, retention time and peak area, and why HPLC is the workhorse of pharmaceutical, food and clinical analysis.
Hund's Rule: Why Electrons Spread Out Before Pairing
Hund's rule of maximum multiplicity explained: electrons occupy degenerate orbitals singly with parallel spins before pairing, why this lowers energy, worked orbital diagrams for carbon, nitrogen, oxygen and iron, unpaired electrons and magnetism, and the link to chromium and copper.
Hydrofluoric Acid: A 'Weak' Acid That's Extremely Dangerous
Why hydrofluoric acid is chemically a weak acid yet one of the most hazardous chemicals in industry: how it penetrates skin, attacks calcium, dissolves glass, and why it's used anyway.
The Hydrogen Emission Spectrum: Lyman, Balmer and Paschen Series
How hydrogen's line spectrum arises from electrons falling between energy levels: the Lyman (ultraviolet), Balmer (visible) and Paschen (infrared) series, why lines converge, reading an energy level diagram, the convergence limit and ionisation energy, and why hydrogen's lines matter in astronomy.
ICP-MS: Measuring Trace Metals
How inductively coupled plasma mass spectrometry measures dozens of elements at parts-per-trillion levels: the argon plasma, ion sampling, mass analysis, interferences, isotope ratios, and uses from water safety to geology.
Identifying Ions: A Qualitative Analysis Flowchart
A practical, step-by-step scheme for identifying the cation and anion in an unknown salt: flame tests, sodium hydroxide and ammonia precipitates, the ammonium test, and tests for carbonate, sulfate, halides and nitrate, in the right order.
How Chemists Identify an Unknown Compound
A step-by-step strategy for identifying an unknown substance: observation, purity checks, elemental analysis, molecular formula from mass spectrometry, functional groups from IR, structure from NMR, and a fully worked example.
Independent, Dependent and Control Variables
How to identify the independent, dependent and control variables in a chemistry experiment, why controlling variables makes a fair test, writing a testable hypothesis, and examples from common practicals.
Indicators and Titration Curves Practice
15 practice questions on acid–base indicators and titration curves: colours at given pH values, choosing indicators, reading curves, pKin and colour ratios, and double-indicator titrations, with explained answers.
Infrared Spectroscopy: How Molecules Vibrate
How infrared spectroscopy identifies functional groups: bond vibrations, wavenumbers, a table of key absorptions, reading an IR spectrum step by step, the fingerprint region, and uses from breathalysers to climate science.
Solving a "Crime" with Ink Chromatography
A complete forensic-style practical: identify which suspect's pen wrote a ransom note using paper chromatography. Includes the scenario, equipment, safety, step-by-step method, a sample results table with Rf values, analysis, evaluation questions and extension ideas.
Insulin: The Protein That Controls Blood Sugar
A chemical profile of insulin: its two-chain structure and disulfide bridges, how it's made from proinsulin, how it lowers blood glucose, the history from Banting and Best to Sanger and recombinant insulin, diabetes, and modern insulin analogues.
Ionic Radius: Why Cations Shrink and Anions Grow
What ionic radius means and how it's measured, why positive ions are smaller than their atoms and negative ions larger, trends down groups and across periods, isoelectronic series, how charge and coordination number affect size, worked ranking examples, and why ionic size matters for lattice energy, solubility and biology.
How Atoms Become Ions: Gaining and Losing Electrons
The energy story behind ion formation: ionisation energy for making cations, electron affinity for making anions, why forming isolated ions usually costs energy, how lattice energy and hydration pay the bill, a Born–Haber style walk-through for sodium chloride, and ions formed in flames, solutions, batteries and the atmosphere.
IR vs NMR Spectroscopy
A clear comparison of infrared and NMR spectroscopy: what each measures, the physics behind them, what information each gives, sample requirements, cost and speed, strengths and blind spots, and how chemists combine them, with worked examples of isomers that one technique can tell apart and the other can't.
Measuring Iron in Supplement Tablets
An advanced practical to find the mass of iron in iron(II) sulfate supplement tablets by redox titration with potassium manganate(VII): the chemistry, method, full worked calculation from sample data, comparison with the label, errors, and an alternative colorimetric method.
Iron in the Body: Haemoglobin and Oxygen Transport
How the body uses about 4 grams of iron: haemoglobin and myoglobin, iron in enzymes, Fe²⁺ vs Fe³⁺ chemistry, how iron is absorbed, transported and stored, why there's no way to excrete it, iron-deficiency anaemia and iron overload.
Isoelectronic Species: Same Electrons, Different Sizes
What isoelectronic means, how to spot isoelectronic atoms, ions and molecules, why radius decreases as nuclear charge increases across an isoelectronic series, trends in ionisation energy, isoelectronic molecules such as N₂, CO and CN⁻, and exam-style ranking questions with answers.
How to Read and Write Isotope Notation (AZX and Element-Mass Forms)
A step-by-step guide to isotope notation: the AZX nuclide symbol, element-mass names like carbon-14, writing ions with charges, notation for particles in nuclear equations, balancing mass and atomic numbers, and common mistakes, with practice questions and answers.
Isotopes vs Isobars vs Isotones
Isotopes share protons, isobars share mass number, isotones share neutrons. A side-by-side comparison with examples, a memory trick, where each idea matters in nuclear chemistry, and practice questions.
Isotopes Practice Questions with Answers
Fourteen isotope practice questions, from counting protons and neutrons to calculating relative atomic mass and finding abundances, with a full worked answer key for every question.
Ka and pKa: Measuring Acid Strength
What the acid dissociation constant Ka and pKa tell you, how to convert between them, a table of common pKa values, and how pKa predicts buffers, indicators and reaction direction.
The Relationship Ka × Kb = Kw
Why the Ka of an acid and the Kb of its conjugate base always multiply to Kw, how to use pKa + pKb = 14, and worked examples on salt solutions, cyanide and ammonium.