Study Help, Organized by Subject

Answer Solutions is a free reference for students who want to understand the concepts behind their coursework. Each guide covers one idea from the ground up — clear language, worked examples, no accounts required.

Latest Guides
  • Biology · June 2026

    Osmosis and Diffusion Explained

    The concentration gradient driving diffusion, how osmosis moves water across selectively permeable membranes, the meaning of isotonic, hypotonic, and hypertonic solutions, facilitated diffusion via channel proteins, aquaporins, active transport, and biological examples from gas exchange to kidney function.

  • History · June 2026

    The Roman Empire: Rise and Fall Explained

    From the end of the Republic and Augustus's Principate through the Pax Romana, the Crisis of the Third Century, Constantine's Christianisation, the division of the empire, and the fall of the Western Roman Empire in 476 AD — causes, events, and enduring legacy.

  • Physics · June 2026

    Vectors and Scalars Explained

    What distinguishes scalar quantities from vectors, how to add vectors using the tip-to-tail and parallelogram methods, resolving vectors into perpendicular components with sine and cosine, finding resultants, and applying vector methods to forces, projectiles, and equilibrium problems.

  • Earth Science · June 2026

    Earthquakes and Seismic Waves Explained

    How elastic rebound on faults generates earthquakes, the difference between focus and epicentre, P-waves vs S-waves vs surface waves, the moment magnitude scale, and how seismologists triangulate an earthquake's location.

  • History · June 2026

    The American Civil War: Causes, Course, and Consequences

    The long-running conflict over slavery and states' rights that split the United States in 1861 — covering secession, the key military turning points, the Emancipation Proclamation, and the promises and failures of Reconstruction.

  • English · June 2026

    Essay Structure and Planning Explained

    A practical framework for planning and writing essays: brainstorming techniques, building an outline, writing effective introductions and conclusions, structuring body paragraphs with evidence and analysis, and using transitions.

  • Mathematics · June 2026

    Probability and Statistics Explained

    Theoretical and experimental probability, combined events, mean, median, mode, standard deviation, the normal distribution and the 68-95-99.7 rule, and common pitfalls like confusing correlation with causation.

  • Physics · June 2026

    Forces and Momentum Explained

    Momentum as mass times velocity, balanced and unbalanced forces, the impulse-momentum theorem, conservation of momentum in closed systems, and the difference between elastic and inelastic collisions — with worked examples.

  • Chemistry · June 2026

    The Periodic Table Explained

    Reading the periodic table as a map of chemical behaviour: periods, groups, blocks, atomic radius trends, ionisation energy, the distinction between metals and non-metals, and using position to predict reactivity and ion charges.

  • Biology · June 2026

    Natural Selection and Evolution Explained

    How heritable variation, differential survival, and reproductive success drive evolutionary change — covering mutation, genetic drift, types of selection, speciation, and the multiple lines of evidence that support the theory.

  • Biology · January 2026

    Mendelian Genetics Explained

    Dominant and recessive alleles, Punnett squares, the law of segregation, independent assortment, dihybrid crosses, and the extensions to Mendel — incomplete dominance, codominance, polygenic traits.

  • Mathematics · January 2026

    Linear Equations and Graphs

    Slope, slope-intercept form, point-slope form, finding x- and y-intercepts, parallel and perpendicular lines, and solving systems of two equations by substitution and elimination.

  • Earth Science · January 2026

    Climate Zones and Biomes Explained

    How latitude, altitude, and ocean currents produce distinct climate zones — and how each zone's temperature and rainfall pattern determines the biome of organisms that live there.

  • English · January 2026

    Reading Comprehension Strategies

    Six evidence-based habits — annotating, questioning, summarising, inferring, visualising, and monitoring — that strong readers use to understand and retain complex texts.

  • Physics · January 2026

    Electricity and Circuits: Voltage, Current, and Resistance

    Ohm's Law (V = IR), series vs. parallel circuits, power calculations, and Kirchhoff's laws — the essential toolkit for analysing any electric circuit.

  • History · January 2026

    The Cold War Explained

    From the Truman Doctrine and Berlin Airlift to the Cuban Missile Crisis, Vietnam, and the fall of the Soviet Union — the ideological rivalry that shaped the second half of the twentieth century.

  • Chemistry · January 2026

    Stoichiometry and Mole Calculations

    The mole concept, molar mass, mole ratios from balanced equations, identifying the limiting reagent, and calculating theoretical vs. actual percentage yield — with worked examples.

  • Biology · January 2026

    Mitosis and Meiosis: Cell Division Explained

    The four stages of mitosis vs. the two rounds of meiosis: what happens at each phase, how crossing over generates genetic diversity, and what non-disjunction errors cause.

  • Earth Science · January 2026

    Volcanoes and Volcanic Eruptions

    How magma composition determines eruption style, the differences between shield volcanoes and stratovolcanoes, and the hazards — pyroclastic flows, lahars, tephra — that make volcanoes deadly.

  • English · January 2026

    Paragraph Structure and Unity

    The PEEL model for academic paragraphs: how to write topic sentences, integrate evidence without quote-dropping, analyse with 'so what?', and link smoothly to the next point.

  • Physics · January 2026

    Waves and Sound: Frequency, Wavelength, and Speed

    The wave equation v = fλ, transverse vs. longitudinal waves, how sound travels through different media, and the Doppler effect — all explained with clear examples.

  • History · January 2026

    The French Revolution: Causes, Events, and Legacy

    From the Estates-General and the fall of the Bastille to the Reign of Terror and Napoleon's coup — the decade that dismantled monarchy and planted the ideas that shaped modern politics.

  • Mathematics · January 2026

    Fractions, Decimals, and Percentages

    Converting between all three forms, adding and multiplying fractions, the three types of percentage problem, and the mental-math shortcuts that make these calculations fast.

  • Chemistry · January 2026

    Acids, Bases, and pH Explained

    Arrhenius and Brønsted-Lowry definitions, strong vs. weak acids, the logarithmic pH scale, neutralisation, and how buffers keep blood and other biological fluids pH-stable.

  • Biology · January 2026

    DNA Replication Explained

    How helicase, primase, DNA polymerase, and ligase work together to copy a cell's entire genome semi-conservatively — including leading strand, Okazaki fragments, and proofreading.

  • Physics · January 2026

    The Laws of Thermodynamics Explained

    The four laws that govern all energy exchange: thermal equilibrium, conservation of energy, entropy increase, and the unreachability of absolute zero — with real-world examples.

  • Science · January 2026

    The Scientific Method Explained

    A step-by-step guide to observation, hypothesis, experiment, data analysis, and conclusion — with worked examples and a clear explanation of how peer review keeps science honest.

  • English · June 2025

    How to Cite Sources in MLA Format

    The two-part MLA system explained: parenthetical in-text citations and Works Cited entries, with formatted examples for books, journals, websites, and anthologies.

  • Earth Science · June 2025

    Understanding Plate Tectonics

    How lithospheric plates move on the asthenosphere, what happens at divergent, convergent, and transform boundaries, and the evidence that confirmed the theory.

  • History · June 2025

    Causes of World War One

    The MAIN framework unpacked — militarism, alliance systems, imperialism, and nationalism — plus the assassination that triggered the chain reaction of 1914.

  • Mathematics · June 2025

    The Pythagorean Theorem

    Everything you need to apply a² + b² = c²: finding missing sides, recognising common triples, checking whether a triangle is a right triangle, and real-world uses.

  • Chemistry · June 2025

    Types of Chemical Bonds

    Ionic, covalent, and metallic bonds compared: how each forms, what determines bond type, and why it predicts a substance's melting point, conductivity, and hardness.

  • Biology · June 2025

    Photosynthesis Explained

    How plants capture sunlight and convert it into glucose — covering the light-dependent reactions, the Calvin cycle, and the factors that control photosynthesis rate.

  • Chemistry · June 2025

    How to Balance Chemical Equations

    Master the law of conservation of mass with a clear step-by-step method for balancing any equation by inspection.

  • Biology · June 2025

    Cellular Respiration Explained

    From glycolysis to the electron transport chain — understand how cells convert glucose into usable energy (ATP).

  • Mathematics · June 2025

    Solving Quadratic Equations: Three Methods

    Factoring, completing the square, and the quadratic formula — when to use each and worked examples for every case.

  • English · June 2025

    How to Write a Strong Thesis Statement

    A clear framework for crafting arguable, specific thesis statements that anchor any essay or research paper.

  • Physics · June 2025

    Newton's Three Laws of Motion Explained

    Concrete examples and real-world applications of inertia, force-acceleration, and action-reaction pairs.

  • Earth Science · June 2025

    Understanding the Water Cycle

    How evaporation, condensation, precipitation, and runoff form a continuous planetary system — with energy explained.