627 articles
All articles — Page 11
Every article in the chemistry library, newest first.
Equivalence Point vs End Point
The equivalence point is where reactants are in exact stoichiometric amounts; the end point is where you see the signal. How they differ, why they don't always match, and how to minimise the gap.
Essential Amino Acids and Where to Find Them
The nine essential amino acids listed one by one, with what each does and good food sources, plus conditionally essential amino acids, complete vs incomplete proteins, protein combining and how much protein adults need.
Exceptions to the Octet Rule: Expanded, Incomplete and Odd-Electron Molecules
A list-style guide to the main exceptions to the octet rule, with Lewis structure examples for each: incomplete octets (BF₃, BeCl₂, AlCl₃), odd-electron radicals (NO, NO₂, ClO₂), expanded octets (PCl₅, SF₆, XeF₄, I₃⁻), transition metal compounds, and how to recognise each type in exam questions.
Ground State vs Excited State Electron Configurations
The difference between ground-state and excited-state electron configurations: definitions, how to tell them apart, how atoms become excited (heat, light, electricity), what happens when they relax, worked examples from sodium to carbon, why excited states explain spectra, flame colours and lasers, and common exam traps.
Experimental Design Practice Questions
Fourteen practice questions on planning chemistry investigations: identifying variables, writing hypotheses, choosing equipment and ranges, control experiments, repeatability, spotting flaws in a method, and suggesting specific improvements, with model answers.
Random vs Systematic Errors
The difference between random and systematic errors in chemistry experiments, how each affects accuracy and precision, how to spot them in data, how to reduce them, and how to write about them in an evaluation.
How Temperature and pH Affect Enzymes
Why enzyme activity rises then crashes with temperature, why each enzyme has an optimum pH, how substrate and enzyme concentration change the rate, and what the classic graphs mean, explained with collision theory and denaturation.
What Makes a Fair Test?
What a fair test is and why it matters: changing one variable at a time, controlling others, repeats, control experiments, validity, reliability and reproducibility, with chemistry examples of fair and unfair tests.
Fatty Acids: Saturated, Unsaturated and Essential
How fatty acid structure controls the properties of fats: chain length, saturated vs unsaturated, cis and trans double bonds, omega-3 and omega-6, essential fatty acids, melting points, hydrogenation and naming shorthand.
Working Backwards: Finding Isotope Abundances from Average Atomic Mass
Step-by-step worked examples for finding the percentage abundance of isotopes when the relative atomic mass is known: the algebra method with x and (100 − x), fraction method, checking answers, three-isotope problems where one abundance is given, and common mistakes.
The Chemistry of Fingerprint Detection
What a fingerprint is made of and how chemistry makes it visible: powders, ninhydrin and its purple product, superglue fuming, iodine, silver nitrate, fluorescent dyes, and how investigators choose the right method for each surface.
Fireworks and Electron Transitions: The Physics Behind the Colours
How fireworks produce their colours: fuel and oxidiser chemistry, heat exciting electrons, the metals behind red, orange, yellow, green, blue and purple, why many colours come from small molecules like SrCl and BaCl, why blue is hardest, incandescence vs luminescence, and modern safer and greener formulas.
Emission Spectra with a Spectroscope: A Classroom Investigation
A school-lab-safe investigation of emission spectra: using a hand-held spectroscope with gas discharge tubes, flame tests and everyday lights to see line spectra, record observations and link them to electron energy levels.
How Food Is Analysed: Labels, Additives and Contaminants
Where the numbers on a nutrition label come from: measuring water, protein by the Kjeldahl and Dumas methods, fat by solvent extraction, carbohydrate by difference, energy, salt, vitamins, additives, contaminants like mycotoxins and pesticides, and food fraud testing.
Analysing Food Dyes with a Colorimeter
A complete practical to measure the concentration of a food dye in a sports drink or sweet coating using a colorimeter: choosing the wavelength, preparing standards by dilution, drawing a calibration graph, calculating the result, sample data, errors and evaluation.
Forensic Chemistry: Science at the Crime Scene
What forensic chemists actually do: identifying drugs, poisons, fire accelerants, gunshot residue, paint, glass and fibres, the instruments they rely on, why chain of custody matters, and how the job differs from what you see on television.
TV Forensics vs Real Forensic Chemistry
What crime dramas get wrong about forensic chemistry: instant results, one machine that identifies anything, perfect matches, enhanced images, luminol proving blood, and lone scientists solving cases, compared with how real forensic labs work and why the differences matter.
What Is a Fume Cupboard For?
How a fume cupboard (fume hood) protects you: airflow and face velocity, the sash as a shield, when you must use one, how to work in one correctly, what it can't protect against, types of fume cupboard, and the checks that keep it safe.
Gas Chromatography: How It Works
How gas chromatography separates volatile compounds: the carrier gas, the column, the oven and detectors, retention times, reading a chromatogram, measuring amounts from peak areas, and GC–MS in forensics and testing.
Gas Chromatography vs HPLC
A detailed comparison of gas chromatography and high-performance liquid chromatography: mobile and stationary phases, which samples each can handle, temperature, detectors, speed, resolution, cost, coupling to mass spectrometry, and a decision guide with real examples.
Glucose: Ring and Chain Forms
How glucose switches between an open chain and a six-membered ring, what α- and β-glucose are, how Fischer and Haworth projections show them, mutarotation, and why the ring form matters for starch, cellulose and sugar tests.
Glycolysis Step by Step
All ten steps of glycolysis with the enzyme, reaction type and energy change for each: the investment and payoff phases, substrate-level phosphorylation, the net yield of 2 ATP and 2 NADH, regulation at PFK-1, and the fates of pyruvate.
Drawing Good Graphs for Chemistry Practicals
How to choose, draw and read graphs in chemistry: line vs bar charts, axes, scales, plotting, lines and curves of best fit, anomalies, gradients and intercepts, with the rules examiners use to award marks.
Gravimetric Analysis with Worked Examples
How gravimetric analysis measures an amount by weighing a pure product: precipitation and volatilisation methods, the steps from precipitating to heating to constant mass, and five fully worked calculations.
Gravimetric Analysis Practice Problems
Twelve gravimetric analysis problems with full solutions: precipitating sulfate as BaSO₄ and chloride as AgCl, gravimetric factors, heating to constant mass, water of crystallisation, thermal decomposition, percentage purity, mixtures and evaluating sources of error.
Haemoglobin: How Blood Carries Oxygen
How haemoglobin loads oxygen in the lungs and releases it in tissues: haem and iron(II), four subunits, cooperative binding and the S-shaped dissociation curve, the Bohr effect, 2,3-BPG, fetal haemoglobin, CO₂ transport and sickle cell disease.
GHS Hazard Pictograms Explained
What each of the nine GHS hazard pictograms means, which chemicals carry them, the signal words Danger and Warning, H and P statements, and how to read a modern chemical label.
The Heisenberg Uncertainty Principle for Chemistry Students
What the Heisenberg uncertainty principle says and doesn't say, the relation Δx·Δp ≥ h/4π, worked estimates for an electron in an atom and a football, why electrons can't have Bohr-style orbits, zero-point energy, why atoms don't collapse, the energy–time relation and spectral line widths, and common misconceptions.
The Henderson–Hasselbalch Equation with Worked Examples
Derive and use the Henderson–Hasselbalch equation: buffer pH from pKa and a ratio, finding the ratio needed for a target pH, buffers made by partial neutralisation, limits of the equation, and biology examples.
Safe Chemistry Experiments You Can Do at Home
Eight home chemistry investigations that run over hours or days, using safe household materials: growing crystals, what makes iron rust, dissolving eggshells, invisible inks, marker chromatography, a density tower, yeast and hydrogen peroxide, and sugar in drinks, with the chemistry explained and safety rules.