All Topics

Every page on this site, by subject.

42eXplore publishes short reference pages on school subjects plus a small set of free classroom calculators. The complete index is below.

Microscopy

Compound Microscope Parts, LabeledEach part, where it sits, and what it actually does.

Objective LensesThe most important lens on the instrument, and how to read its markings.

Condenser and Iris DiaphragmThe two controls that decide whether you can see anything.

Stage and FocusHolding the specimen still, and bringing it into focus without breaking anything.

Brightfield and Phase ContrastThe default mode, its one big failure, and the fix.

Fluorescence MicroscopyMaking the specimen the light source.

Inverted MicroscopesObjectives below the stage, and the problems that arrangement solves.

Microscope Labelling WorksheetFourteen parts to label, with an answer key and function questions.

Classroom calculators

Boolean Algebra CalculatorEnter an expression. Get the truth table, minterms, SOP and POS.

Truth Table GeneratorFull truth table for any expression up to six variables.

Number Base ConverterConvert between bases 2 to 36, and see the working.

Calculators by subject

Percentages and RatiosFour calculators, and the distinctions students lose marks on.

Fraction CalculatorsConverting between the three ways of writing the same number.

Algebra CalculatorsFactors, quadratics, regression and limits.

Statistics CalculatorsSpread, and the three distributions taught first.

Grade CalculatorsWhat you need on the final, and what your GPA actually is.

Chemistry CalculatorsMolar mass, density and dilution.

Every calculator

Ratio CalculatorSimplify a ratio, split a total, or solve for a missing term.

Percent Change CalculatorIncrease or decrease measured against a starting value.

Percent Difference CalculatorComparing two values when neither one is the baseline.

Fraction to Percent CalculatorAny fraction, converted and shown as working.

Decimal to Fraction CalculatorTerminating or repeating, reduced to lowest terms.

Fraction to Decimal CalculatorDivide the numerator by the denominator, and know what you will get.

Improper Fraction CalculatorImproper to mixed, and mixed back to improper.

GCF and LCM CalculatorGreatest common factor, least common multiple, and the factorisations behind them.

Quadratic Formula CalculatorRoots, discriminant, vertex and axis of symmetry.

Quadratic Regression CalculatorThe best-fit parabola through a set of points.

Limit CalculatorWhat a function approaches, evaluated from both sides.

Standard Deviation CalculatorSample or population, with the full working.

Probability Distribution CalculatorBinomial, normal and Poisson, with cumulative values.

Final Grade CalculatorThe score you need on the final, and what happens if you miss it.

GPA CalculatorUnweighted, honors or AP weighted, adjusted for credits.

Molar Mass CalculatorAny formula, with the working and percent composition.

Density CalculatorLeave one field blank and it solves for that one.

Dilution CalculatorC1V1 = C2V2, solved for whichever value you leave blank.

Worked molar masses

Molar Mass of H2SO4Sulfuric Acid — 98.072 g/mol.

Molar Mass of NaOHSodium Hydroxide — 39.997 g/mol.

Molar Mass of HClHydrochloric Acid — 36.458 g/mol.

Molar Mass of NH3Ammonia — 17.031 g/mol.

Molar Mass of CO2Carbon Dioxide — 44.009 g/mol.

Molar Mass of Cl2Chlorine Gas — 70.900 g/mol.

Molar Mass of Ca(OH)2Calcium Hydroxide — 74.092 g/mol.

Molar Mass of H2OWater — 18.015 g/mol.

Molar Mass of NaClSodium Chloride — 58.440 g/mol.

Molar Mass of Na2SO4Sodium Sulfate — 142.036 g/mol.

Molar Mass of NH4ClAmmonium Chloride — 53.489 g/mol.

Molar Mass of Na3PO4Sodium Phosphate — 163.940 g/mol.

Subject indexes

Science topicsLife, earth, physical science and lab technique

Social studies topicsHistory, cultures, geography and the built environment

English and language artsReading, writing, literature and language

Every other topic

Glaciers · Rivers · Volcanoes · Earthquakes · Weather · Clouds · Tornadoes · Wind · Snow · Polar Regions · Deserts · Rocks · Minerals and Identification · Soil · Whales · Snakes · Specific Snakes · Hedgehogs · Owls · Marsupials · Penguins · Eggs · Trees and Forests · Invasive Species · Global Warming · Recycling · Classical Music · Jazz · Jazz Musicians · Folk Music · Rock and Roll · Rock and Roll History · Musical Instruments · Dance · Masks · Pottery · Fibre and Fabric · Calligraphy · Drawing · Photography · Woodworking · Construction · Bridge Building · Architecture · Iron and Steel · Astronomy · The Night Sky · Light · Electricity · Scientists and Inventors in Electricity · Nikola Tesla · Simple Machines · Flight · Inventors and Inventions · Shakespeare · Charles Dickens · Mark Twain · Sign Language · Native American Tribes and Cultures · Lewis and Clark · The Nuclear Age · Basketball · The Circus · Chocolate · Pumpkins · Vitamins and Nutrition

Reading, writing and literature

Skimming and ScanningTwo fast reading rates, and the tasks each one is actually for.

Journal WritingLow-stakes writing, and what it is actually for.

The Writing ProcessFive stages that do not run in order.

PoetryForm, sound, and meter.

Figurative LanguageLanguage that means something other than it literally says.

Story ElementsThe parts of a narrative and how they hold together.

Tall TalesDeliberate exaggeration as a narrative form.

Fantasy and Science FictionTwo genres of the impossible, divided by how they justify it.

MysteryA genre built on withheld information.

Mathematics and data

Number SystemsPlace value, bases, and how to convert between them.

StatisticsCentre, spread, and shape.

Graphs and ChartsMatching the display to the data.

Geometric Shapes and FiguresHow shapes are classified, and why the definitions matter.

PiOne ratio, the same for every circle.

FractalsShapes that repeat their own structure at every scale.

Life science

Animal Tracks and SignIdentifying wildlife from what it leaves behind.

BeesColony life, pollination, and decline.

InsectsThe largest class of animals, and how to recognise one.

WormsThree unrelated phyla sharing one common name.

Frogs and ToadsAmphibians, metamorphosis, and permeable skin.

The Skeletal SystemStructure, function, and living tissue.

The Respiratory SystemMoving air, and exchanging gas.

BirdsFeathers, flight, and how birders identify what they see.

WolvesPack structure, and what happens to a system without them.

BearsEight species, and why their winter sleep is not true hibernation.

Earth and marine science

Tide PoolsA habitat defined by twice-daily extremes.