PrepOK

Plot up to eight labelled points on a Cartesian grid you can size from -5 to -20, by dragging or by typing coordinates, and read off each quadrant plus the distance and midpoint between points.

Hover or arrow-key across a 12×12 multiplication chart to light up any times-table fact, with an area model that shows why a × b is a rectangle of that many squares.

Type any angle in degrees or radians, or drag the point, and read exact values for sine, cosine, and tangent, with a full chart of all sixteen special angles.

Drag a, b, and c on a live graph of y = ax² + bx + c and watch the vertex, axis of symmetry, roots, and y-intercept respond, with the vertex formula, discriminant, and a full worked example.

Drag one anchor point and set a slope: the point-slope equation writes itself with live numbers, next to the same line rewritten in slope-intercept form.

Drag points A and B on a grid and watch the dashed rise-over-run triangle, the slope formula, and the line's equation update live, including the zero and undefined slope cases.

Drag the Slope m and Intercept b sliders and the line y = mx + b redraws live: b pins the y-intercept at (0, b), m sets the rise for every run of 1, with a worked graphing recipe and examples.

Steer two lines with slope and intercept sliders; the crossing point is the solution of the system. Make the slopes equal to see the parallel (no solution) and same-line (infinitely many) cases.

Drag the parabola's vertex and h and k follow it in y = a(x - h)² + k; stretch or flip with a against the y = x² ghost, and watch the expanded standard form rewrite itself live.

Type in your own isotope masses and abundances to get the weighted average, work backwards from an average to the abundances, or find which element an atomic mass belongs to.

Set the coefficients on a real reaction and watch a live atom tally check both sides. Learn why every element must balance (conservation of mass) with steppers and a 'Show me' answer.

Subtract the two electronegativities to get ΔEN, then read off the bond type. A chart of 30 bonds sorted by polarity, what δ+ and δ− mean, and why polar bonds can still make a nonpolar molecule.

Pick any element from hydrogen to krypton and watch its ground-state electron configuration and Bohr shell diagram build up in Aufbau order, including the chromium and copper exceptions.

Build the Bohr model of any element (Z 1-118). Pick an atomic number to see the nucleus and electron shells fill, with electrons-per-shell and outer-shell count.

Explore all 118 elements in an interactive periodic table: recolor by category, state, or block, and open any element for its electron configuration, Bohr model, and uses.

Pick two elements and compare their electronegativity. The ΔEN difference predicts an ionic, covalent (polar or nonpolar), or metallic bond.

Draw the Lewis dot structure of common molecules. See bonds as lines, lone pairs as dots, count valence electrons, and meet the octet-rule exceptions.

Read the mole ratio straight off the balanced coefficients, then use it to hop from any substance to any other. A table of 57 ratios for 13 common reactions, and a grams-to-grams calculator.

Every VSEPR shape in one chart, with electron geometry, bond angles, hybridization and AXE notation. Look a shape up by molecule, or by counting bonds and lone pairs.

A free build-a-molecule sandbox: tap atoms into the tray, bond them, and watch real molecules snap together. 42 to discover, and it tells you when you are close.

Group 18 is the noble gases: helium, neon, argon, krypton, xenon, radon and oganesson. All seven with their notation, boiling points and glow colours, and why a full outer shell stops them reacting.

A free periodic table memorization game. Drill the first 20, a single family, or all 118: every element you miss comes back until you place it right. No signup.

The electronegativity trend in actual numbers, a colour map of all 118 elements by electronegativity, ionization energy or electron affinity, and what each trend does and why.

Add heat to ice and watch it melt then boil on a live heating curve: the temperature plateaus at 0 and 100 °C while energy breaks bonds. Covers the states, phase changes, and latent heat.

Every gas law with its formula, its graph and a worked example: Boyle's, Charles's, Gay-Lussac's, Avogadro's, Dalton's, Graham's, the combined law and PV = nRT, plus R in six sets of units.

Convert mass to moles, moles to mass, or either to a number of particles, for any formula you type. Molar masses are added up atom by atom with the arithmetic shown.

Heat, squeeze, and cool a live box of atoms to watch pressure, the speed distribution, and even melting and boiling emerge from the collisions. Kinetic theory you can play with.

Which pH values count as acids and which as bases, what every number from 0 to 14 means, the pH of common substances, and a calculator linking pH, pOH, [H⁺] and [OH⁻].

Classify reactions as synthesis, decomposition, single replacement, double replacement, or combustion, then use each pattern to predict the products.

Pick a main-group element and see its Lewis electron-dot symbol. Learn the group rule that gives valence electrons for groups 1, 2, and 13 to 18.

Set two carts' masses, speeds, and elasticity, then collide them. Momentum is conserved in every collision, elastic or inelastic, but kinetic energy is lost unless the collision is perfectly elastic.

Pull a block and watch static friction rise to match your force until it breaks free and slides under a lower, constant kinetic friction, with a live force-vs-pull graph and coefficient sliders.

Drop a hammer and a feather with air resistance on or off, on Earth, the Moon, Mars or Jupiter. In a vacuum they land together, because free-fall acceleration g is the same for every mass.

Enter any two of force, mass, and acceleration and this F = ma calculator solves the third instantly, with a free-body box that accelerates and a worked-steps line for every answer.

Drag points to shape a distance-time or velocity-time graph and a runner moves to match. See why slope is speed or acceleration, and the area under a velocity-time line is distance.

One sandbox for all three of Newton's laws: glide with no net force, accelerate at a = F/m on a live velocity-time graph, and push off to see equal and opposite forces.

Set any two of voltage, current, and resistance and watch the third solve itself with V = I × R. A live circuit lights a bulb whose brightness tracks the power.

Set launch speed and angle, fire the projectile, and watch it trace a real parabola. Read range, maximum height and time of flight, and see why 45 degrees gives the longest range.

Change a lever, ramp, pulley, or wheel and axle and watch mechanical advantage and effort force update live. Every simple machine trades distance for force, so work in equals work out.

Animate a travelling wave, adjust its amplitude, wavelength, and frequency, switch between transverse and longitudinal motion, and watch wave speed (v = f × λ) and period (T = 1/f) update live.

Drag the force arrows on an object and the net force updates live, with a balanced-or-unbalanced verdict. Build free-body diagrams and find when an object accelerates.

Slide along the electromagnetic spectrum from radio waves to gamma rays and watch wavelength, frequency, and photon energy update together, with a rainbow swatch in the visible band.

Click any organelle on a labeled cell to see its one-line job, then flip to a name-that-job quiz that scores you. Covers the nucleus, mitochondria, ER, Golgi, ribosomes, and the plant-only parts.

Click or tab through a labeled animal cell to explore the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, lysosome, vacuole, and more, each with its job explained.

Toggle one cell between plant and animal to watch the cell wall, chloroplasts, and large central vacuole appear while the shared parts stay. Includes a turgor slider and a live plant-vs-animal Venn.

A live membrane splits a beaker of water and solute particles. Watch osmosis pull water to the saltier side, diffusion spread solute out, tonicity swell or shrink a cell, and a pump spend ATP.

Click through an interactive water-cycle scene (evaporation, condensation, precipitation, and collection, plus transpiration and runoff) with a kid-friendly explanation for each stage.

A live map of the Solar System. It opens on today, showing where every planet actually is right now, computed from NASA/JPL orbital data. Jump to any date, or press play.