627 articles
All articles — Page 15
Every article in the chemistry library, newest first.
Photoelectric Effect Calculations: Work Function and Kinetic Energy
Worked examples using Einstein's photoelectric equation hf = φ + KE_max: threshold frequency and wavelength, maximum kinetic energy and speed of photoelectrons, stopping potential, working in joules and electronvolts, reading a KE vs frequency graph to find Planck's constant, and intensity questions.
Photons and Energy Levels: Why Atoms Emit Specific Colours
How quantised energy levels and photons explain the colours of flames, fireworks, neon signs and street lamps: ground and excited states, the relationship E = hf, why each element has its own colours, fluorescence and phosphorescence, lasers, and why molecules and solids give broader colours.
Photosynthesis: The Chemistry
Photosynthesis as chemistry: the overall equation and its energy, where the oxygen comes from, the two stages inside the chloroplast, redox and light energy, limiting factors, and why photosynthesis matters for food, fuel and the atmosphere.
Photosynthesis vs Respiration
Photosynthesis and respiration compared side by side: equations, energy, where and when they happen, redox, ATP, the organelles and electron transport chains involved, compensation points, and how the two processes cycle carbon and oxygen.
pOH and pH: Converting Between Them
What pOH measures, why pH + pOH = 14 at 25 °C, how to move between pH, pOH, [H⁺] and [OH⁻], and how temperature changes the rule, with worked examples.
Polyprotic Acids: Stepwise Dissociation
How acids with more than one acidic proton ionise one step at a time: Ka1, Ka2 and Ka3, why each step is weaker, the true pH of sulfuric acid, phosphate species and carbonic acid.
Starch vs Glycogen vs Cellulose
Three polymers of glucose with completely different jobs. Compare amylose, amylopectin, glycogen and cellulose: α and β links, branching, shape, solubility, digestibility and why the tiny structural difference matters so much.
Potentiometric Titrations
How measuring electrode potential during a titration locates the equivalence point precisely: indicator and reference electrodes, pH titrations, redox titrations with platinum electrodes, derivative plots and automatic titrators.
Required Practicals: A Skills Checklist
A self-assessment checklist of the core practical skills chemistry students need: safe working, measuring mass and volume, heating, titration, separation, preparing solutions, recording data, drawing graphs and evaluating errors, with what 'good' looks like for each and how to practise.
Precipitation Titrations: Mohr's Method
How chloride and other halides are measured by titration with silver nitrate: Mohr's method with chromate indicator, Volhard's back titration with thiocyanate, Fajans' adsorption indicators, worked examples and sources of error.
How to Predict the Charge of an Ion from the Periodic Table
A step-by-step method for predicting ion charges from group numbers: metals in groups 1, 2 and 13, non-metals in groups 15, 16 and 17, noble gases, why hydrogen is special, transition metals with variable charges and Roman numerals, common polyatomic ions, worked examples writing formulas, and exceptions.
How to Prepare a Buffer Solution
Three practical methods for making a buffer of a chosen pH: mixing a weak acid with its salt, partial neutralisation, and mixing two salts. Includes calculations, lab steps, pH meter calibration and troubleshooting.
Propagating Uncertainties Through Calculations
How uncertainties combine in sums, products, powers and logarithms, the simple and quadrature rules, uncertainty from repeated measurements (standard deviation and standard error), with chemistry examples from titrations to Ka.
Protein Folding: How Chains Find Their Shape
How an unfolded chain of amino acids finds one precise 3D shape: Anfinsen's experiment, the hydrophobic effect, Levinthal's paradox and folding funnels, chaperones, misfolding diseases such as Alzheimer's and prions, and AI structure prediction.
Primary, Secondary, Tertiary and Quaternary Protein Structure
The four levels of protein structure explained: amino acid sequence, α-helices and β-sheets, the 3D fold held by hydrophobic interactions, hydrogen bonds, ionic bonds and disulfide bridges, and multi-subunit proteins like haemoglobin.
Transcription and Translation from a Chemist's View
How cells turn a DNA sequence into a protein, focusing on the chemistry: RNA polymerase and template strands, mRNA processing, the genetic code, charging tRNA with ATP, the ribosome as a ribozyme, peptide bond formation and the energy cost of a protein.
Proteins: Chains of Amino Acids
A beginner's guide to proteins: how amino acids link into chains, how chains fold into shapes, the many jobs proteins do, why shape decides function, what denaturation is, protein in the diet and how proteins are made.
Qualitative Analysis Practice Questions
Twenty practice questions on identifying ions and compounds, from single flame tests to multi-step unknowns, each with a full worked answer explaining the reasoning, the equations and the common traps.
Qualitative vs Quantitative Analysis
The difference between finding out what's in a sample and how much of it there is: definitions, methods, examples, and how chemists combine qualitative tests and quantitative measurements in real analysis.
Quantum Chemistry Misconceptions
Nine persistent myths about quantum mechanics in chemistry, from electrons as tiny planets and spinning balls to 'observation creates reality' and hybrid orbitals as physical objects, each with the correct picture explained.
The Quantum Mechanical Model of the Atom
An overview of the modern quantum mechanical model of the atom: how it grew out of the Bohr model, its key ideas (wave behaviour, quantised energy, orbitals, probability, four quantum numbers), how it explains the periodic table and bonding, what it predicts that earlier models couldn't, and how to describe it in exams.
Quantum Numbers Practice Questions (with Answer Key)
Twenty-four graded practice questions on quantum numbers: allowed values of n, l, mₗ and mₛ, naming orbitals, counting orbitals and electrons, spotting impossible sets, assigning quantum numbers to electrons, nodes and exam-style explanations, with a full answer key and explanations.
Quarks, Gluons and What Protons Are Made Of
A clear introduction to the particles inside protons and neutrons: up and down quarks and their fractional charges, gluons and the strong force, why quarks are never found alone, where the proton's mass really comes from, how deep inelastic scattering revealed quarks, and why chemists can mostly ignore them.
Raman Spectroscopy
How Raman spectroscopy identifies molecules from the tiny fraction of laser light they scatter with changed energy: Rayleigh vs Raman scattering, Raman shift, how it complements infrared, and uses from drug checking to art and Mars.
Make a Red Cabbage pH Indicator
A safe, low-cost practical: extract anthocyanin indicator from red cabbage, test household substances, build your own pH colour scale, and understand the chemistry behind the colours.
Benedict's Test for Reducing Sugars
A school-lab guide to Benedict's test: the redox chemistry behind the colour change, a safe step-by-step method, semi-quantitative colour scale, testing sucrose by acid hydrolysis, results tables and sources of error.
Calculating Relative Atomic Mass from Isotope Abundances
Worked examples for calculating relative atomic mass from isotope masses and percentage abundances, including chlorine, copper, magnesium and boron, data from mass spectra, using exact isotopic masses, three-isotope problems, and why the periodic table values aren't whole numbers.
Relativistic Effects in Chemistry: Why Mercury Is Liquid
How Einstein's relativity changes the chemistry of heavy elements: fast inner electrons, the contraction of s orbitals and expansion of d and f orbitals, why gold is yellow and noble, why mercury is a liquid, the inert pair effect in thallium and lead, relativity in car batteries, and what it means for superheavy elements.
Calculating Rf Values
How to measure and calculate Rf values in paper and thin-layer chromatography, with worked examples, identifying unknowns, what affects Rf, common mistakes and practice questions with answers.
How to Write a Risk Assessment for a Chemistry Practical
A step-by-step guide to writing a risk assessment for a chemistry experiment: identifying hazards, assessing risks, choosing control measures, emergency actions and disposal, with a completed example for a titration.