Concept Lab

83 simulations · 121 explorers · 64 mechanisms · 1 joined lab

Units and measurements

Physics · Class 11 · 2 labs

Vernier callipers: Close the jaws on an object, slide the loupe along the vernier to find the line that matches, and correct the reading for zero error.

Explorer

Units and measurements

Vernier callipers

Screw gauge: Turn the thimble onto a wire, read the pitch and circular scales, and correct for zero error and backlash.

Explorer

Units and measurements

Screw gauge

Kinematics

Physics · Class 11 · 5 labs

Relative velocity: Row a boat across a flowing river and find the heading that beats the current.

Simulation

Motion in a plane

Relative velocity

Motion graphs: Set how a body speeds up and slows down, and watch its position, velocity and acceleration graphs draw themselves.

Simulation

Motion in a straight line

Motion graphs

Projectile motion: Change angle, speed and height and watch range, time of flight and max height follow the formula.

Simulation

Motion in a plane

Projectile motion

Projectile on an incline: Launch up a slope and find the angle that carries it furthest along the surface.

Simulation

Motion in a plane

Projectile on an incline

Uniform circular motion: Speed stays constant while velocity keeps changing. Watch where the acceleration actually points.

Simulation

Motion in a plane

Uniform circular motion

Laws of motion

Physics · Class 11 · 5 labs

Pulley and connected bodies: Hang two masses over a pulley and see what sets the acceleration and the tension.

Simulation

Laws of motion

Pulley and connected bodies

Friction on an incline: Tilt the slope until the block finally lets go, then watch friction drop the moment it slides.

Simulation

Laws of motion

Friction on an incline

Head-on collisions: Collide two bodies at any restitution and check what survives the impact.

Simulation

Centre of mass and collisions

Head-on collisions

Pseudo force in accelerated frames: Speed up a truck or a lift with a pendulum inside, and watch it tilt, seen from the ground and from inside.

Simulation

Laws of motion

Pseudo force in accelerated frames

Banked road: Take a banked curve too fast or too slow and see which way the car slides.

Simulation

Laws of motion

Banked road

Work, energy and power

Physics · Class 11 · 2 labs

Force and potential energy curves: Let a particle go on a potential energy curve and watch the work its force does turn into speed.

Simulation

Work, energy and power

Force and potential energy curves

Vertical circle: Swing a ball on a string in a vertical loop and find the slowest speed that still works.

Simulation

Work, energy and power

Vertical circle

Rotational motion

Physics · Class 11 · 6 labs

Centre of mass: Burst a flying shell into two pieces and follow the point between them that never leaves the parabola.

Simulation

Centre of mass and collisions

Centre of mass

Forces and torques in equilibrium: Hang a weight from two strings, load a beam, lean a ladder and balance a metre scale, and watch the forces and moments cancel.

Explorer

Rotational motion

Forces and torques in equilibrium

Angular momentum: Pull the spinning masses inward and watch the spin rate answer.

Simulation

Rotational motion

Angular momentum

Moment of inertia and axes: Pick a rod, ring, disc, sphere or plate, then slide or turn the axis and watch I and the radius of gyration change.

Explorer

Rotational motion

Moment of inertia and axes

Rolling race: Roll a sphere, a disc and a ring down the same slope and see which shape wins.

Simulation

Rotational motion

Rolling race

Ball striking a rod: Roll a ball into a pinned or free rod, and watch what the hit keeps and what it loses.

Simulation

Rotational motion

Ball striking a rod

Gravitation

Physics · Class 11 · 4 labs

Orbits and Kepler's laws: Give a satellite a sideways push and see whether it circles, loops or escapes.

Simulation

Gravitation

Orbits and Kepler's laws

How g changes: Travel from the centre of a planet out into space and read g the whole way.

Simulation

Gravitation

How g changes

Escape velocity: Fire a body straight up and find the speed at which it never comes back.

Simulation

Gravitation

Escape velocity

Satellites and geostationary orbit: Raise a satellite's altitude and watch it slow down until it keeps pace with the ground.

Simulation

Gravitation

Satellites and geostationary orbit

Properties of solids and liquids

Physics · Class 11 · 6 labs

$Stress and strain: Stretch a wire, squeeze a cube or shear a block and watch the point move along its stress-strain graph, past the elastic limit to fracture.$

Explorer

Properties of solids and liquids

Stress and strain

Pressure and buoyancy: Push on the liquid, change the densities and let a cube go: watch every gauge and the depth it floats at.

Simulation

Mechanical properties of fluids

Pressure and buoyancy

Viscosity and terminal velocity: Drop a steel ball into glycerine, change its size and the liquid, and time it between two marks to find the viscosity.

Simulation

Mechanical properties of fluids

Viscosity and terminal velocity

Bernoulli and fluid flow: Follow one parcel of liquid through a venturi and watch it speed up where the pressure falls.

Simulation

Mechanical properties of fluids

Bernoulli and fluid flow

Surface tension and capillary rise: Dip a fine tube into a liquid, change its radius, the contact angle and the liquid, and watch how high the column climbs.

Simulation

Mechanical properties of fluids

Surface tension and capillary rise

Searle's apparatus: Load the wire in half-kilogram steps, turn the micrometer until the spirit level's bubble is centred again, and work out Young's modulus from the extension.

Explorer

Properties of solids and liquids

Searle's apparatus

Thermal properties of matter

Physics · Class 11 · 4 labs

Thermal expansion: Drag the thermometer to heat a rod, plate, block, flask of liquid, bimetal strip or pendulum clock, and watch how much each one grows.

Explorer

Thermal properties of matter

Thermal expansion

Calorimetry: Drop hot metal, ice, copper sulphate or acid into a calorimeter and watch the water settle where heat lost equals heat gained.

Simulation

Thermal properties of matter

Calorimetry

Conduction, convection and radiation: Change the rod, the air and the surface of a hot block and watch how fast it cools, and which way the heat leaves.

Simulation

Thermal properties of matter

Conduction, convection and radiation

Blackbody spectrum: Heat a body and watch its glow curve climb and its peak slide toward blue.

Explorer

Thermal properties of matter

Blackbody spectrum

Thermodynamics

Physics · Class 11 · 1 lab

P–V diagram cycles: Take a gas round a Carnot, Otto or rectangular cycle and read the work off as area.

Simulation

Thermodynamics

P–V diagram cycles

Kinetic theory of gases

Physics · Class 11 · 1 lab

Simulation

Kinetic theory

Kinetic theory of gases

Oscillations and waves

Physics · Class 11 · 8 labs

Simple harmonic motion: Watch a mass on a spring beside the rotating circle its motion is a shadow of.

Simulation

Oscillations

Simple harmonic motion

Incline, floor and spring: One block, three chapters: release it down a slope, across a rough floor and into a spring, and watch the energy move from height to speed to heat.

Simulation

Putting it together

Incline, floor and spring

Simple pendulum: Change the string, the swing and the air drag, and time the pendulum to measure g.

Simulation

Oscillations

Simple pendulum

Damping and resonance: Add damping, then drive the oscillator and hunt for the frequency it responds to hardest.

Simulation

Oscillations

Damping and resonance

Simulation

Waves

Waves on a string

Sound in open and closed pipes: Change the pipe, the gas and its temperature, and watch the air inside stand in a sound wave.

Simulation

Waves

Sound in open and closed pipes

Beats and the Doppler effect: Two close frequencies throbbing, and a siren shifting pitch as it passes.

Simulation

Waves

Beats and the Doppler effect

Resonance tube: Lower the water under a ringing tuning fork to find the two loud spots, then work out the speed of sound and the end correction.

Explorer

Oscillations and waves

Resonance tube

Electrostatics

Physics · Class 12 · 5 labs

Electric field and potential: Walk a probe past two charges and find that the field and the potential hit zero in different places.

Simulation

Electrostatics

Electric field and potential

Electric dipole in a field: Change the charges, their spacing and the field, let the dipole go and watch the torque swing it like a pendulum.

Simulation

Electrostatics

Electric dipole in a field

Gauss's law: Grow a closed surface, add up the field crossing it, and watch the total refuse to move.

Simulation

Electrostatics

Gauss's law

Capacitors and dielectrics: Slide a slab in with the battery on, then with it off, and get opposite answers.

Simulation

Electrostatics

Capacitors and dielectrics

Capacitors in series and parallel: Wire capacitors in series or parallel and watch the charge and voltage split up.

Explorer

Electrostatics

Capacitors in series and parallel

Current electricity

Physics · Class 12 · 4 labs

Drift velocity and resistivity: Change the metal, its temperature and the field, and watch electrons race about yet drift slowly along the wire.

Simulation

Current electricity

Drift velocity and resistivity

DC circuit builder: Place cells, resistors, bulbs, keys and meters on a board and watch every current and voltage answer at once.

Explorer

Current electricity

DC circuit builder

Metre bridge: Slide the jockey until the needle nulls, and let the balance point name the unknown.

Simulation

Current electricity

Metre bridge

Post office box: Pull plugs out of a post office box, press the keys and watch the needle kick left or right, until you have the coil's resistance to a hundredth of an ohm and its specific resistance.

Explorer

Current electricity

Post office box

Magnetic effects of current and magnetism

Physics · Class 12 · 10 labs

Magnetic field of a current: Walk a probe away from a wire, a coil or a solenoid and chart how the field fades.

Simulation

Moving charges and magnetism

Magnetic field of a current

Charge in a magnetic field: Fire a charge into a magnetic field and watch it curve into a circle or a helix.

Simulation

Moving charges and magnetism

Charge in a magnetic field

Helix in a magnetic field: Tilt a charge's velocity away from the field and watch its circle stretch into a glowing 3D helix.

Simulation

Moving charges and magnetism

Helix in a magnetic field

Crossed electric and magnetic fields: An electric field, a magnetic field and gravity all pull on one charged grain at once. Watch the loops march along a line that does not care what the charge is.

Simulation

Putting it together

Crossed electric and magnetic fields

Accelerate, bend, land: A charge is accelerated through a voltage, bent by a magnet and coasts to a screen. Change the mass and watch where it lands move. This is how a mass spectrometer works.

Simulation

Putting it together

Accelerate, bend, land

Force between current-carrying wires: Float one wire on the magnetic push of another: change the currents and the wire's weight, and watch where it bobs.

Simulation

Moving charges and magnetism

Force between current-carrying wires

Moving-coil galvanometer: Pass a current through a coil on a spring and watch it turn; change the turns, the field, the spring and the damping.

Simulation

Moving charges and magnetism

Moving-coil galvanometer

Bar magnet and its field: Turn a bar magnet and an electric dipole in 3D, move a probe along the axis or the equator and compare the fields.

Explorer

Magnetic effects of current and magnetism

Bar magnet and its field

Magnetic materials: Put bismuth, aluminium, an iron salt, soft iron or steel in a field, change the temperature and watch χ, Curie's law and the hysteresis loop.

Explorer

Magnetism and matter

Magnetic materials

Galvanometer by half deflection: Pick R for a large even deflection, then close the shunt key and turn S until the needle halves, and work out the galvanometer's resistance and figure of merit.

Explorer

Magnetic effects of current and magnetism

Galvanometer by half deflection

Electromagnetic induction and alternating currents

Physics · Class 12 · 5 labs

Faraday's law and Lenz's law: Push a magnet through a coil and watch the induced current fight the change.

Simulation

Electromagnetic induction

Faraday's law and Lenz's law

LR and LC circuits: Grow a current in a coil through a resistor, then switch it to a capacitor and watch the energy swing between them.

Simulation

Electromagnetic induction

LR and LC circuits

RC charging and discharging: Charge and drain a capacitor, and find out what the time constant actually means.

Simulation

Current electricity

RC charging and discharging

LCR circuits and phasors: Turn the driving frequency and watch the phasors line up at resonance.

Simulation

Alternating current

LCR circuits and phasors

AC generator and transformer: Turn a coil in a magnet and feed its emf to a transformer: change the speed, the turns and the load.

Simulation

Alternating current

AC generator and transformer

Electromagnetic waves

Physics · Class 12 · 1 lab

Simulation

Electromagnetic waves

Electromagnetic wave

Optics

Physics · Class 12 · 8 labs

Lenses and mirrors: Move the object across the focus and watch the image flip, grow and go virtual.

Simulation

Ray optics

Lenses and mirrors

$Refraction and total internal reflection: Drag a ray across a surface and watch it bend, shift through a slab or get trapped in a fibre.$

Explorer

Ray optics

Refraction and total internal reflection

Microscope and telescope: Line up two lenses, then a microscope and a telescope, and watch the image grow.

Explorer

Ray optics

Microscope and telescope

Prism and dispersion: Send a ray through a prism, watch it bend twice, and see why white light comes out as a spectrum.

Simulation

Ray optics

Prism and dispersion

Huygens wavefronts: Send a wavefront at a surface and build the new one from wavelets, step by step.

Explorer

Wave optics

Huygens wavefronts

Young's double slit: Change slit spacing and wavelength and watch the fringe pattern breathe.

Simulation

Wave optics

Young's double slit

Polarisation of light: Turn polaroids and swing a ray onto glass, and watch the light meter follow Malus's law and the reflected light lose its p part at Brewster's angle.

Explorer

Optics

Polarisation of light

Focal length by the u-v method: Slide the image needle until it moves with the real image as your eye moves, then read u and v off the bench and work out the focal length of a concave mirror or a convex lens.

Explorer

Optics

Focal length by the u-v method

Dual nature of matter and radiation

Physics · Class 12 · 2 labs

Photoelectric effect: Change the light's frequency and intensity and see which one actually matters.

Simulation

Dual nature of matter

Photoelectric effect

de Broglie wavelength: Speed up an electron, proton or alpha particle and read the wavelength of its matter wave.

Explorer

Dual nature of matter

de Broglie wavelength

Atoms and nuclei

Physics · Class 12 · 6 labs

Rutherford scattering: Change the α's energy, its aim and the nucleus, fire it, and watch how close it gets and how far it turns.

Simulation

Atoms

Rutherford scattering

Bohr model and spectra: Push an electron between orbits and watch the spectral line it emits.

Simulation

Atoms

Bohr model and spectra

From one atom to one electron: A hydrogen atom drops a level and emits a photon; that photon lands on a metal. Pick the transition, pick the metal, and see whether an electron comes off at all.

Joins 2

Putting it together

From one atom to one electron

X-ray tube and Moseley's law: Turn up the tube voltage, change the target, and watch the X-ray spectrum's cutoff and lines.

Explorer

Atoms

X-ray tube and Moseley's law

Simulation

Nuclei

Radioactive decay

Binding energy curve: Pick a nucleus, find its mass defect, and see why splitting and joining both release energy.

Explorer

Nuclei

Binding energy curve

Electronic devices

Physics · Class 12 · 2 labs

pn junction and rectifier: Bias a diode both ways, trace its curve, then use it to rectify or to hold a voltage steady.

Simulation

Semiconductor electronics

pn junction and rectifier

Logic gates: Flip the inputs of AND, OR, NOT, NAND and NOR gates, fill in their truth tables and build every gate from NANDs or NORs alone.

Explorer

Semiconductor electronics

Logic gates

Some basic concepts in chemistry

Chemistry · Class 11 · 1 lab

Limiting reagent: Mix two reactants for a balanced equation and see which runs out, what forms, what is left over and that the mass stays the same.

Explorer

Some basic concepts in chemistry

Limiting reagent

States of matter: gases and liquids

Chemistry · Class 11 · 2 labs

Real gas isotherms: Change the temperature and drag along a van der Waals isotherm to see where a real gas leaves PV = RT and where it liquefies.

Explorer

States of matter: gases and liquids

Real gas isotherms

Vapour pressure of a liquid: Seal a liquid in a flask at a temperature you pick and watch evaporation and condensation even out at its vapour pressure, then find where it boils.

Simulation

States of matter: gases and liquids

Vapour pressure of a liquid

Atomic structure

Chemistry · Class 11 · 2 labs

Atomic orbitals: Pick n, l and mₗ, then turn the orbital in three dimensions and count its nodes.

Explorer

Atomic structure

Atomic orbitals

Electronic configuration: Pick an element and watch Aufbau, Pauli and Hund fill its orbital boxes, then see why chromium and copper break the rule.

Explorer

Atomic structure

Electronic configuration

Chemical bonding and molecular structure

Chemistry · Class 11 · 4 labs

VSEPR and molecular shape: Set the bond pairs and lone pairs, then watch the shape and the angles settle.

Simulation

Chemical bonding

VSEPR and molecular shape

Hybrid orbitals: Mix s and p (and d) orbitals into hybrids, then bond them: σ head-on, π side by side.

Explorer

Chemical bonding and molecular structure

Hybrid orbitals

Molecular orbital diagrams: Fill the orbitals of H₂ to Ne₂ and their ions, and turn each orbital in three dimensions.

Explorer

Chemical bonding and molecular structure

Molecular orbital diagrams

Intermolecular forces: Pick two molecules and see which forces hold each liquid together, then compare their boiling points and solubility in water.

Explorer

Chemical bonding and molecular structure

Intermolecular forces

Chemical thermodynamics

Chemistry · Class 11 · 2 labs

Hess's law and Born–Haber cycle: Walk both routes of an enthalpy cycle and use Hess's law to find the one step nobody can measure, such as a lattice enthalpy.

Explorer

Chemical thermodynamics

Hess's law and Born–Haber cycle

Gibbs energy and spontaneity: Drag the temperature to see when ΔG = ΔH − TΔS turns negative, then read K from ΔG° and which way a reaction runs from Q.

Explorer

Chemical thermodynamics

Gibbs energy and spontaneity

Equilibrium

Chemistry · Class 11 · 4 labs

Simulation

Equilibrium

Le Chatelier's principle

Titration curves: Run base in from a burette and watch pH crawl, jump, then flatten again.

Simulation

Ionic equilibrium

Titration curves

Solubility product and common ion: Run a common ion into a solution of the metal ion and watch the ionic product climb until it meets Ksp and the solid appears.

Simulation

Equilibrium

Solubility product and common ion

Salt analysis: Add reagents to an unknown salt, one test at a time, and find its cation and anion from what you see.

Explorer

Equilibrium

Salt analysis

Classification of elements and periodicity

Chemistry · Class 11 · 1 lab

Periodic trends: Walk across a period or down a group and watch the chosen property rise or fall.

Simulation

Classification of elements

Periodic trends

Purification and characterisation of organic compounds

Chemistry · Class 11 · 1 lab

Lassaigne's test: Fuse an unknown compound with sodium, test the extract, and find which of N, S, a halogen and P it holds.

Explorer

Purification and characterisation of organic compounds

Lassaigne's test

Some basic principles of organic chemistry

Chemistry · Class 11 · 3 labs

Stereoisomers: Build a molecule in 3-D with its wedge-dash, sawhorse and Newman drawings, swap groups and mirror it, and tell enantiomers, diastereomers and meso forms apart.

Explorer

Some basic principles of organic chemistry

Stereoisomers

Chirality and mirror images: Turn a molecule and its mirror image in 3D and try to lay one on the other.

Explorer

Some basic principles of organic chemistry

Chirality and mirror images

Electronic effects: Put alkyls, benzene rings, a double bond, para groups or fluorines on a carbocation, radical or carbanion, and rank how stable it is.

Explorer

Some basic principles of organic chemistry

Electronic effects

Hydrocarbons

Chemistry · Class 11 · 12 labs

Conformations of alkanes: Turn the back carbon of ethane or butane and watch the 3-D, wedge-dash, sawhorse and Newman drawings and the energy curve follow.

Explorer

Hydrocarbons

Conformations of alkanes

Free-radical halogenation: Light splits chlorine into atoms, and a chain of single-electron steps swaps a hydrogen of methane for a chlorine.

Mechanism

Hydrocarbons

Free-radical halogenation

Markovnikov addition: HBr adds across a double bond, and carbocation stability decides which carbon gets what.

Mechanism

Hydrocarbons

Markovnikov addition

Halogen addition to alkenes: Bromine bridges both carbons of a double bond, so the bromide has to come in from the other face.

Mechanism

Hydrocarbons

Halogen addition to alkenes

Peroxide effect: A trace of peroxide turns HBr addition into a radical chain, and the bromine lands on the end carbon of propene.

Mechanism

Hydrocarbons

Peroxide effect

Ozonolysis: Ozone snips a double bond in half and hands back two carbonyl compounds.

Mechanism

Hydrocarbons

Ozonolysis

Catalytic hydrogenation: Hydrogen splits on a metal surface and adds to ethene one atom at a time, both from the same face.

Mechanism

Hydrocarbons

Catalytic hydrogenation

Hydration of alkynes: Water adds to propyne with a mercury catalyst, and the enol it makes turns straight into a ketone.

Mechanism

Hydrocarbons

Hydration of alkynes

Aromaticity: Turn benzene and four other rings in 3D, merge their p orbitals into a π cloud and test each against the 4n + 2 rule.

Explorer

Hydrocarbons

Aromaticity

Mechanism

Hydrocarbons

Nitration of benzene

Friedel–Crafts reactions: Aluminium chloride rips a chlorine off, and the ion left behind is hungry enough to attack benzene.

Mechanism

Hydrocarbons

Friedel–Crafts reactions

Directing effects in aromatic substitution: Phenol's OH pushes electrons round the ring, so bromine attacks the para carbon and not meta.

Mechanism

Hydrocarbons

Directing effects in aromatic substitution

Solutions

Chemistry · Class 12 · 1 lab

Raoult's law and colligative properties: Mix two liquids and compare their vapour pressure with Raoult's line, then add a solute or dissolve a gas and work out the change.

Explorer

Solutions

Raoult's law and colligative properties

Redox reactions and electrochemistry

Chemistry · Class 12 · 3 labs

Molar conductivity: Find the cell constant, then measure κ and Λm across a dilution series and extrapolate Λm against √c to Λ°.

Explorer

Redox reactions and electrochemistry

Molar conductivity

Galvanic cell and Nernst: Pick two metals, set the concentrations, and read the voltage the cell actually makes.

Simulation

Electrochemistry

Galvanic cell and Nernst

Electrolysis: Pass a known current for a known time and weigh what plates out.

Simulation

Electrochemistry

Electrolysis

Chemical kinetics

Chemistry · Class 12 · 1 lab

Rate laws and order: Watch a reactant disappear and read the order off whichever plot comes out straight.

Simulation

Chemical kinetics

Rate laws and order

Solid state

Chemistry · Class 12 · 1 lab

Unit cells and packing: Turn a cubic cell in three dimensions and read the count, packing and density off it.

Simulation

Solid state

Unit cells and packing

Surface chemistry

Chemistry · Class 12 · 1 lab

Adsorption isotherms: Change the pressure and the temperature to see how much gas a solid holds, and read Freundlich's k and 1/n off a straight log plot.

Explorer

Surface chemistry

Adsorption isotherms

d- and f-Block elements

Chemistry · Class 12 · 1 lab

d-Block and lanthanoid trends: Walk the 3d row and the lanthanoids, and watch radius, ionisation enthalpy, oxidation states and spin-only moment change.

Explorer

d- and f-Block elements

d-Block and lanthanoid trends

Coordination compounds

Chemistry · Class 12 · 2 labs

Geometry of complexes: Turn complexes in three dimensions, read their hybridisation off the boxes and count their isomers.

Explorer

Coordination compounds

Geometry of complexes

Crystal field splitting: Split the d orbitals with ligands, weigh Δ against the pairing energy and see the colour that results.

Explorer

Coordination compounds

Crystal field splitting

Isolation of metals

Chemistry · Class 12 · 1 lab

Ellingham diagram: Pick an oxide and a reductant, drag the temperature, and read off the diagram whether the metal can be extracted.

Explorer

Isolation of metals

Ellingham diagram

Organic compounds containing halogens

Chemistry · Class 12 · 7 labs

E2 elimination: Base grabs a proton while the leaving group departs, all in one step, forming a double bond.

Mechanism

Haloalkanes and haloarenes

E2 elimination

SN2 substitution: One concerted step: the nucleophile attacks from behind and the molecule turns inside out.

Mechanism

Haloalkanes and haloarenes

SN2 substitution

SN1 substitution: The leaving group goes first, and the flat carbocation it leaves behind decides the product.

Mechanism

Haloalkanes and haloarenes

SN1 substitution

Carbocation rearrangement: A hydrogen slides one carbon across, taking its electrons with it, and the skeleton changes.

Mechanism

General organic chemistry

Carbocation rearrangement

Grignard reagents: A carbon so negative it attacks a carbonyl directly, welding two skeletons together.

Mechanism

Alcohols, phenols and ethers

Grignard reagents

Wurtz–Fittig reaction: Sodium turns an aryl halide into a carbon nucleophile that joins a methyl group onto the ring, one electron at a time.

Mechanism

Organic compounds containing halogens

Wurtz–Fittig reaction

SNAr on a haloarene: Hydroxide adds to a nitro-activated chloroarene, the charge parks on a nitro oxygen, then chloride leaves.

Mechanism

Organic compounds containing halogens

SNAr on a haloarene

Organic compounds containing oxygen

Chemistry · Class 12 · 21 labs

Hydroboration–oxidation: Borane adds across C=C with boron on the less crowded carbon, then peroxide swaps boron for OH.

Mechanism

Organic compounds containing oxygen

Hydroboration–oxidation

Functional group tests: Test an unknown compound with NaHCO₃, FeCl₃, Lucas, 2,4-DNP, Tollens, Fehling, Hinsberg and carbylamine, and name its functional group.

Explorer

Organic compounds containing oxygen

Functional group tests

E1 elimination: The same carbocation as SN1, but this time a proton leaves instead of a nucleophile arriving.

Mechanism

Haloalkanes and haloarenes

E1 elimination

Acid and base strength: Pick two acids or two amines and compare their pKa or pKb, then see what steadies the charge on one and not the other.

Explorer

Organic compounds containing oxygen

Acid and base strength

Cumene process: Air turns cumene into a hydroperoxide, then acid makes the phenyl group hop onto oxygen to give phenol and acetone.

Mechanism

Organic compounds containing oxygen

Cumene process

Reimer–Tiemann reaction: Chloroform and alkali make dichlorocarbene, the phenoxide ring catches it ortho, and hydroxide turns CHCl₂ into CHO.

Mechanism

Organic compounds containing oxygen

Reimer–Tiemann reaction

Kolbe's reaction: The phenoxide ring attacks carbon dioxide ortho to the O⁻, and acid turns the salt into salicylic acid.

Mechanism

Organic compounds containing oxygen

Kolbe's reaction

Cleavage of ethers: HI puts a proton on the ether oxygen, then iodide pushes out the smaller group by SN2.

Mechanism

Organic compounds containing oxygen

Cleavage of ethers

Nucleophilic addition to C=O: Cyanide adds to the δ+ carbon of a polar C=O, and the alkoxide takes a proton from HCN.

Mechanism

Organic compounds containing oxygen

Nucleophilic addition to C=O

Étard reaction: Chromyl chloride turns toluene's CH₃ into the Étard complex, and water releases benzaldehyde.

Mechanism

Organic compounds containing oxygen

Étard reaction

Gattermann–Koch reaction: CO and HCl with AlCl₃ build the formyl cation, and benzene attacks it to become benzaldehyde.

Mechanism

Organic compounds containing oxygen

Gattermann–Koch reaction

Rosenmund reduction: Hydrogen on poisoned palladium swaps the Cl of an acid chloride for H and stops at the aldehyde, shown as a schematic.

Mechanism

Organic compounds containing oxygen

Rosenmund reduction

Stephen reduction: Tin(II) and acid turn a nitrile into an iminium salt, and water sets the aldehyde free.

Mechanism

Organic compounds containing oxygen

Stephen reduction

Mechanism

Organic compounds containing oxygen

Clemmensen reduction

Wolff–Kishner reduction: Hot base walks a hydrazone's C=N–NH₂ down to CH₂ as nitrogen gas leaves.

Mechanism

Organic compounds containing oxygen

Wolff–Kishner reduction

Aldol condensation: Two aldehydes join through an enolate, then warming throws out water to leave a double bond.

Mechanism

Aldehydes, ketones and acids

Aldol condensation

Cannizzaro reaction: With no alpha hydrogen to give up, one aldehyde hands a hydrogen to another.

Mechanism

Aldehydes, ketones and acids

Cannizzaro reaction

Haloform reaction: Iodine replaces the three hydrogens of a methyl group one by one until CI₃ is cut off as yellow iodoform.

Mechanism

Organic compounds containing oxygen

Haloform reaction

Kolbe electrolysis: Single electrons leave ethanoate ions at the anode, CO₂ breaks off and two methyl radicals join into ethane.

Mechanism

Organic compounds containing oxygen

Kolbe electrolysis

Hell–Volhard–Zelinsky reaction: Red phosphorus and bromine put a bromine on the carbon next to COOH, and the enol does the attacking.

Mechanism

Organic compounds containing oxygen

Hell–Volhard–Zelinsky reaction

Nucleophilic acyl substitution: Aniline adds to an acid chloride's C=O, then chloride is pushed out to leave acetanilide.

Mechanism

Organic compounds containing oxygen

Nucleophilic acyl substitution

Organic compounds containing nitrogen

Chemistry · Class 12 · 6 labs

Carbylamine reaction: Chloroform and alkali make a carbene that turns a primary amine into a foul-smelling isocyanide.

Mechanism

Organic compounds containing nitrogen

Carbylamine reaction

Gabriel phthalimide synthesis: Phthalimide's anion takes one alkyl group by SN2, then hydrolysis sets a pure primary amine free.

Mechanism

Organic compounds containing nitrogen

Gabriel phthalimide synthesis

Hofmann bromamide degradation: The alkyl group moves from carbon to nitrogen, and the amide loses one carbon as CO₂.

Mechanism

Organic compounds containing nitrogen

Hofmann bromamide degradation

Azo coupling: A diazonium ion attacks the para carbon of aniline and joins two rings into a yellow dye.

Mechanism

Organic compounds containing nitrogen

Azo coupling

Diazotisation: Cold nitrous acid turns the NH₂ of aniline into N≡N⁺, one proton move at a time.

Mechanism

Organic compounds containing nitrogen

Diazotisation

Sandmeyer reaction: Copper(I) hands over one electron, N₂ bubbles off and a chlorine takes its place.

Mechanism

Organic compounds containing nitrogen

Sandmeyer reaction

Biomolecules

Chemistry · Class 12 · 1 lab

Glucose ring and anomers: The OH on C5 of glucose adds to its own aldehyde group, closing a six-membered ring with a new OH on C1.

Mechanism

Biomolecules

Glucose ring and anomers

Polymers

Chemistry · Class 12 · 1 lab

Free-radical polymerisation: A radical from benzoyl peroxide adds to ethene again and again, building a polythene chain until two chain ends meet.

Mechanism

Polymers

Free-radical polymerisation

Sets and relations

Mathematics · Class 11 · 1 lab

Venn diagrams: Pick a set expression and set how many elements sit in each region, and watch the regions shade and the count check n(A ∪ B) and De Morgan's laws.

Explorer

Sets and relations

Venn diagrams

Functions

Mathematics · Class 11 · 2 labs

Transforming graphs: Pick a base graph and a rule, drag P along the result and watch which point of the base it came from.

Explorer

Functions

Transforming graphs

Explorer

Functions

Special functions

Complex numbers

Mathematics · Class 11 · 3 labs

The Argand plane: Drag z and w on the Argand plane: sums add as arrows, products turn and stretch, and the conjugate is a mirror image.

Explorer

Complex numbers

The Argand plane

Roots of unity: The nth roots of 1 sit at the corners of a regular polygon; add them tip to tail and they close up to 0.

Explorer

Complex numbers

Roots of unity

Loci in the Argand plane: Pick a condition on z and move z to trace its locus: a circle, a perpendicular bisector, a ray or an ellipse.

Explorer

Complex numbers

Loci in the Argand plane

Quadratic equations

Mathematics · Class 11 · 1 lab

Roots of a quadratic: Slide a, b and c: the parabola meets the x-axis at the roots, D decides their nature, and a complex pair shows up on a small Argand plane.

Explorer

Quadratic equations

Roots of a quadratic

Binomial theorem

Mathematics · Class 11 · 1 lab

Pascal's triangle: Pick a row n, a term r and the numbers a and b, and watch the triangle give each term of (a + b)ⁿ, its middle and greatest terms and the row sums.

Explorer

Binomial theorem

Pascal's triangle

Sequences and series

Mathematics · Class 11 · 2 labs

Progressions and their sums: Set a, d or r and drag the first two bars, and watch the terms build a staircase of sums that climbs, runs away or levels off at its limit.

Explorer

Sequences and series

Progressions and their sums

A.M. and G.M.: Drag the join of a and b along the diameter of a semicircle and watch the radius (A.M.), the half-chord (G.M.) and the H.M. compare, with means inserted between a and b.

Explorer

Sequences and series

A.M. and G.M.

Trigonometry

Mathematics · Class 11 · 3 labs

The unit circle: Turn a point round the unit circle and unwrap sin, cos and tan into their graphs; radians as arc length; periods and signs by quadrant.

Explorer

Trigonometry

The unit circle

Trigonometric identities: Stacked right triangles prove sin(A + B) and cos(A + B); double and half angles as presets; both sides of an identity plotted to coincide.

Explorer

Trigonometry

Trigonometric identities

Trigonometric equations: Draw y = k across sin, cos or tan: every crossing is marked and labelled by the general-solution formula as n changes.

Explorer

Trigonometry

Trigonometric equations

Coordinate geometry: points and straight lines

Mathematics · Class 11 · 4 labs

Centres of a triangle: Drag a triangle's corners and watch its centroid, orthocentre, circumcentre and incentre move, with the Euler line, the section formula, the area by determinant and a shifted origin.

Explorer

Coordinate geometry: points and straight lines

Centres of a triangle

Locus tracer: Pick a rule, drag A, B and P, and watch P trace its path while the equation from the rule lands on it.

Explorer

Coordinate geometry: points and straight lines

Locus tracer

Forms of a straight line: Drag two points to set a line and read every form of its equation; add a second line for the angle between them, and a point for its distance to the line.

Explorer

Coordinate geometry: points and straight lines

Forms of a straight line

Families of lines: Move λ or drag a point T and watch L₁ + λL₂ = 0 swing about the point where two lines meet; test a third line for concurrency and show the angle bisectors.

Explorer

Coordinate geometry: points and straight lines

Families of lines

Circles

Mathematics · Class 11 · 1 lab

Explorer

Circles

Conic sections

Mathematics · Class 11 · 3 labs

Slicing a cone: Tilt a plane through a double cone and watch circle, ellipse, parabola and hyperbola appear; the Dandelin spheres find the focus and the directrix.

Explorer

Conic sections

Slicing a cone

Parabola, ellipse and hyperbola: Pick a conic, set a and b, and drag P along it while PS and PM keep the same ratio e.

Explorer

Conic sections

Parabola, ellipse and hyperbola

Tangents to conics: Drag P along a parabola, ellipse or hyperbola and watch its tangent, its normal and a ray from the focus bouncing off it.

Explorer

Conic sections

Tangents to conics

Limits and continuity

Mathematics · Class 11 · 1 lab

Limits: Slide two points in on x = a from either side and watch the heights they close in on, through holes, jumps and 0/0.

Explorer

Limits and continuity

Limits

Statistics

Mathematics · Class 11 · 1 lab

Mean, spread and standard deviation: Drag the dots of a data set along a number line and watch the mean, median, mode, mean deviation and standard deviation change, beside a set with the same mean and a different spread.

Explorer

Statistics

Mean, spread and standard deviation

Probability

Mathematics · Class 11 · 1 lab

Simulation

Probability

Probability by repeated trials

Sets and relations

Mathematics · Class 12 · 1 lab

Relations and mappings: Tap pairs in and out of a relation on its grid and watch the arrow diagram, the reflexive, symmetric and transitive checks, the classes and the function test answer.

Explorer

Sets and relations

Relations and mappings

Functions

Mathematics · Class 12 · 1 lab

Explorer

Functions

One-one, onto and inverse functions

Matrices and determinants

Mathematics · Class 12 · 2 labs

Matrices as transformations: A 2 × 2 matrix stretches, turns and flips the grid: see products as two moves, det as the area factor and the inverse undoing it.

Explorer

Matrices and determinants

Matrices as transformations

Systems of linear equations: Turn a system's equations into lines or planes and see one solution, a whole line of them or none, with the determinant beside them.

Explorer

Matrices and determinants

Systems of linear equations

Trigonometry

Mathematics · Class 12 · 1 lab

Inverse trigonometric functions: Restrict sin, cos and tan to their principal branch and reflect; sin⁻¹(sin x) as a sawtooth; identities like sin⁻¹x + cos⁻¹x = π/2 on the graph.

Explorer

Trigonometry

Inverse trigonometric functions

Vectors

Mathematics · Class 12 · 2 labs

Explorer

Vectors

Vectors, dot and cross products

Explorer

Vectors

Triple products

Three-dimensional geometry

Mathematics · Class 12 · 2 labs

Lines in space: Join two points in space or set two lines: distance, section point, direction cosines, and whether the lines meet, run parallel or are skew.

Explorer

Three-dimensional geometry

Lines in space

Planes in space: Tilt a plane by its normal and measure a point's distance from it, the angle between two planes and between a line and a plane.

Explorer

Three-dimensional geometry

Planes in space

Limits and continuity

Mathematics · Class 12 · 1 lab

Explorer

Continuity and differentiability

Differentiation

Mathematics · Class 12 · 2 labs

Secant to tangent: Type a function, slide Q towards P and watch the secant turn into the tangent as its slope settles on f′(x).

Explorer

Differentiation

Secant to tangent

Explorer

Differentiation

Implicit differentiation

Applications of derivatives

Mathematics · Class 12 · 3 labs

Related rates: Pull a ladder's foot, pour water into a cone or pump up a balloon at a set rate, and watch the linked rate match the chain rule.

Simulation

Applications of derivatives

Related rates

Curve sketching with derivatives: Slide a line across f, f′ and f″ stacked and see where f rises, falls and bends, and which flat points are peaks, dips or neither.

Explorer

Applications of derivatives

Curve sketching with derivatives

Mean value theorem: Drag A and B along a curve you type and find every point c where the tangent runs parallel to the chord AB.

Explorer

Applications of derivatives

Mean value theorem

Definite integrals and areas

Mathematics · Class 12 · 3 labs

Riemann sums: Slide n up and watch left, right, midpoint and trapezium strips close in on the area under your curve.

Explorer

Definite integrals and areas

Riemann sums

Fundamental theorem: Sweep x and watch the area under f become a curve of its own, whose slope at every x is f(x).

Explorer

Definite integrals and areas

Fundamental theorem

Area between curves: Type two curves, snap to where they cross and add up the region between them by columns or by rows.

Explorer

Definite integrals and areas

Area between curves

Differential equations

Mathematics · Class 12 · 2 labs

Slope fields: Type dy/dx = f(x, y), drag the start point and watch the solution curve follow the field to the exact answer.

Explorer

Differential equations

Slope fields

Growth, decay and cooling: Pick growth, decay, cooling, logistic or arithmetic growth, set the rate and the start, and watch the equation's curve land on the separated solution; plant growth phases and a population's J- and S-shaped curves as presets.

Simulation

Differential equations

Growth, decay and cooling

Probability

Mathematics · Class 12 · 2 labs

Explorer

Probability

Conditional probability and Bayes

Random variables and distributions: Build a distribution bar by bar or pick a binomial, watch its mean and spread marked on the bars, and draw a sample that settles on them as it grows.

Explorer

Probability

Random variables and distributions

Diversity in living world

Biology · Class 11 · 1 lab

Animal body plans: Tap radial and bilateral bodies, two or three germ layers, coelomate, pseudocoelomate and acoelomate sections, segments and the notochord; the tour and worked examples name each phylum from its combination, as Table 4.1 does.

Explorer

Animal kingdom

Animal body plans

Structural organisation in animals and plants

Biology · Class 11 · 5 labs

Plant morphology: Tap the parts of a flowering plant, root types and the regions of the root tip, a leaf, its venation, compound leaves and phyllotaxy; racemose against cymose inflorescence (the apex keeps growing, or ends in a flower); a flower's four whorls and aestivation; and modified roots, stems and leaves.

Explorer

Morphology of flowering plants

Plant morphology

Floral formula: Build a flower whorl by whorl (symmetry, number and fusion of parts, aestivation, ovary position, placentation); the floral diagram and the floral formula write themselves; presets for mustard (Brassicaceae) and Solanaceae, and a quiz that reads a formula back to a family.

Explorer

Morphology of flowering plants

Floral formula

Seed and fruit: Open a bean seed beside a maize grain and tap seed coat, cotyledon, embryonal axis, plumule, radicle, endosperm, aleurone layer, scutellum, coleoptile and coleorhiza; follow ovary to fruit and ovule to seed, then true, false and parthenocarpic fruits.

Explorer

Morphology of flowering plants

Seed and fruit

Plant anatomy: Transverse sections of dicot and monocot root, stem and leaf side by side; peel the epidermal, ground and vascular tissue systems, tap any tissue for its cells and role; radial, conjoint open and conjoint closed bundles; dorsiventral against isobilateral leaf.

Explorer

Anatomy of flowering plants

Plant anatomy

Frog: morphology and anatomy: Tap a frog's external features, then peel its dissection layer by layer: digestive system, heart and lungs, kidneys; lay the male and female reproductive systems side by side and label the dissection.

Explorer

Structural organisation in animals

Frog: morphology and anatomy

Cell structure and function

Biology · Class 11 · 5 labs

The cell: Switch a bacterium, a plant cell and an animal cell and tap every part: cell envelope, mesosome, ribosomes, inclusion bodies; ER, Golgi, lysosomes, vacuoles and the secretory route through them; nucleus with envelope, pores, chromatin, nucleolus and chromosomes by centromere position; compare panel lists what each cell lacks.

Explorer

Cell: the unit of life

The cell

Organelle ultrastructure: Zoom into the organelles the textbook draws in section: fluid mosaic membrane with proteins and carbohydrate chains, cell wall layers, mitochondrion (cristae, matrix), chloroplast (grana, stroma lamellae), 70S and 80S ribosomes, and the 9+2 axoneme against the 9+0 centriole in cross-section.

Explorer

Cell: the unit of life

Organelle ultrastructure

Protein structure: Turn a polypeptide from its primary sequence through the alpha helix and beta pleated sheet to a folded tertiary chain and the four subunits of haemoglobin; pick out peptide bonds, the N and C termini, hydrogen bonds and a disulphide bond.

Explorer

Biomolecules

Protein structure

Enzyme activity: Vary substrate concentration, temperature and pH and read the velocity: the curve rising to Vmax with Km at half of it, the optimum temperature and pH, a competitive inhibitor, and the activation energy with and without the enzyme.

Explorer

Biomolecules

Enzyme activity

Mechanism

Cell cycle and cell division

Plant physiology

Biology · Class 11 · 7 labs

Absorption and action spectra: Absorption spectra of chlorophyll a, chlorophyll b and the carotenoids against the action spectrum of photosynthesis; toggle pigments, sweep the wavelength, see where accessory pigments fill the gaps.

Explorer

Photosynthesis in higher plants

Absorption and action spectra

Light reactions: Step electrons through the Z scheme on a thylakoid membrane from PS II to PS I to NADP⁺, split water for O₂, watch protons pile up in the lumen and drive ATP synthase, then switch to cyclic flow.

Mechanism

Photosynthesis in higher plants

Light reactions

Calvin cycle and the C4 pathway: Turn the Calvin cycle six times for one glucose (carboxylation by RuBisCO, reduction, regeneration of RuBP) and count 18 ATP and 12 NADPH; switch to a C4 plant for the mesophyll and bundle sheath route, or let O₂ bind RuBisCO.

Mechanism

Photosynthesis in higher plants

Calvin cycle and the C4 pathway

Factors affecting photosynthesis: Plot the rate of photosynthesis against light intensity, CO₂ concentration or temperature with the other factors held; the curve flattens where another factor limits (Blackman); C3 against C4 presets.

Explorer

Photosynthesis in higher plants

Factors affecting photosynthesis

Glycolysis and fermentation: Step glucose to two pyruvic acid through the ten reactions with ATP and NADH tallied, then take away oxygen and see which fate of pyruvic acid keeps NAD⁺ coming back.

Mechanism

Respiration in plants

Glycolysis and fermentation

Krebs' cycle: Turn the Krebs' cycle for one acetyl CoA and count the CO₂, NADH + H⁺, FADH₂ and ATP it makes, then lead in from pyruvic acid, fats or proteins to see why the pathway is amphibolic.

Mechanism

Respiration in plants

Krebs' cycle

Electron transport system: Pass the electrons of NADH or FADH₂ from complex to complex to oxygen on the inner mitochondrial membrane, watch protons flow back through ATP synthase, and add up the 38 ATP from one glucose.

Mechanism

Respiration in plants

Electron transport system

Human physiology

Biology · Class 11 · 12 labs

Mechanism of breathing: Breathe in and out and watch the diaphragm and ribs move, the intra-pulmonary pressure fall below atmospheric and air flow in; a trace of the air in the lungs shows the tidal, reserve and residual volumes and the capacities they add to.

Simulation

Breathing and exchange of gases

Mechanism of breathing

Oxygen dissociation curve: Partial pressures of O₂ and CO₂ at the alveoli, blood and tissues drive exchange; the sigmoid oxygen dissociation curve moves right with more pCO₂, H⁺ and temperature; read the O₂ given up per 100 mL of blood and how CO₂ travels.

Explorer

Breathing and exchange of gases

Oxygen dissociation curve

Blood groups: Give a donor's blood to a recipient and see whether antibodies meet their antigens, follow an Rh-ve mother through two Rh+ve pregnancies, and cross the parents' Iᴬ, Iᴮ and i alleles to see their children's groups.

Explorer

Body fluids and circulation

Blood groups

Human heart: Turn a 3-D heart, cut it open to its four chambers and peel it: septa, valves, chordae tendinae, the nodal tissue (SAN, AVN, AV bundle, bundle of His, Purkinje fibres) and the great vessels; follow a red blood cell through the pulmonary and systemic circulation; an artery's wall beside a vein's.

Explorer

Body fluids and circulation

Human heart

Cardiac cycle and ECG: Run the 0.8 s cardiac cycle: atria and ventricles contract in turn, valves open and shut, and the ECG's P, QRS and T run in step; change heart rate and stroke volume and read the cardiac output.

Simulation

Body fluids and circulation

Cardiac cycle and ECG

Nephron and urine formation: Follow filtrate down a labelled nephron: glomerular filtration, reabsorption and secretion by segment, the medullary gradient built by the counter-current loop and vasa recta; switch ADH and the renin-angiotensin response and see urine volume and concentration change.

Simulation

Excretory products and their elimination

Nephron and urine formation

Muscle contraction: Step a contraction from the motor neuron signal: Ca++ binds troponin, myosin heads form cross bridges with ATP, pull and let go, and the sarcomere shortens with the A band constant and the I band and H zone narrowing.

Mechanism

Locomotion and movement

Muscle contraction

Skeleton and joints: Tap the bones of the skull, vertebral column, rib cage, girdles and limbs with the textbook's bone counts, then compare fibrous, cartilaginous and synovial joints and the five synovial examples.

Explorer

Locomotion and movement

Skeleton and joints

Nerve impulse: Stimulate an axon: Na+ and K+ gradients keep the membrane polarised, a stimulus lets Na+ rush in and the reversed polarity travels down the axon; at a chemical synapse vesicles release neurotransmitters that open channels on the next neuron.

Simulation

Neural control and coordination

Nerve impulse

Human brain: Turn a 3-D brain and cut it down the middle: cerebrum and its lobes, grey and white matter, corpus callosum, thalamus, hypothalamus, midbrain, pons, cerebellum and medulla, each tapped for its role; zoom out to the CNS, PNS and visceral nervous system.

Explorer

Neural control and coordination

Human brain

Endocrine glands: A body diagram of the endocrine glands (hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, adrenal, pancreas, gonads, and the heart, kidney and gut as hormone sources), with the pituitary, thyroid and adrenal up close; tap a gland to see its hormones, their targets and what excess or lack causes; label-the-diagram quiz.

Explorer

Chemical coordination and integration

Endocrine glands

Mechanism

Chemical coordination and integration

Mechanism of hormone action

Reproduction

Biology · Class 12 · 6 labs

Pollen grain and embryo sac: Switch between anther and ovule and step a mother cell to a pollen grain or a 7-celled embryo sac, watching the ploidy at every stage.

Mechanism

Sexual reproduction in flowering plants

Pollen grain and embryo sac

Double fertilisation: Choose compatible or incompatible pollen and follow the pollen tube into a synergid, to a 2n zygote and a 3n primary endosperm nucleus.

Mechanism

Sexual reproduction in flowering plants

Double fertilisation

Human reproductive systems: Tap every part the textbook labels in the male and female reproductive systems, peel them layer by layer and follow the ducts (testes, ducts, accessory glands; ovaries, oviduct regions, uterine wall, mammary gland); label-the-diagram quiz.

Explorer

Human reproduction

Human reproductive systems

Gametogenesis: Follow one germ cell to sperms and one to an ovum, and watch the chromosome number per cell fall from 46 to 23.

Mechanism

Human reproduction

Gametogenesis

Menstrual cycle: Run a 28-day cycle: FSH, LH, estrogen and progesterone curves beside the growing follicle and the endometrium; the LH surge releases the ovum at mid-cycle; fertilise the ovum and the corpus luteum stays.

Simulation

Human reproduction

Menstrual cycle

Fertilisation and implantation: Step one ovum from fertilisation in the ampulla through cleavage to implantation, and choose the sperm's X or Y and the path to the placenta or the germ layers.

Mechanism

Human reproduction

Fertilisation and implantation

Genetics and evolution

Biology · Class 12 · 12 labs

Mendelian crosses: Pick Mendel's pea traits and the parents' genotypes, fill the Punnett square box by box and watch the phenotype and genotype ratios build; switch to incomplete dominance, co-dominance or a polygenic trait whose bars become a bell.

Explorer

Principles of inheritance and variation

Mendelian crosses

Linkage and recombination: Drag a second gene along the chromosome and watch recombinant gametes rise from Morgan's 1.3 per cent for yellow and white to 37.2 per cent for white and miniature, then put the genes on different chromosomes and see independent assortment return.

Explorer

Principles of inheritance and variation

Linkage and recombination

Sex determination and sex-linked inheritance: Cross the sex chromosomes of humans, grasshoppers and birds and see which gamete decides the sex, follow the honey bee's fertilised and unfertilised eggs, and watch haemophilia and colour blindness pass from carrier mothers to their sons.

Explorer

Principles of inheritance and variation

Sex determination and sex-linked inheritance

Pedigree analysis: Tap people in a family chart to mark who is affected, test each mode of inheritance and see which fit and why, and find a person's chance of being a carrier, with sickle-cell anaemia, thalassemia and phenylketonuria families.

Explorer

Principles of inheritance and variation

Pedigree analysis

The search for genetic material: Run Griffith's mouse experiment with S and R strains and heat-killed S, test the transforming principle with proteases, RNases and DNase, then follow Hershey and Chase's radioactive phages through infection, blending and centrifuging.

Mechanism

Molecular basis of inheritance

The search for genetic material

DNA double helix: Turn a nucleotide, a polynucleotide strand and the antiparallel double helix with A=T and G≡C pairs, 10 bp per turn, a 3.4 nm pitch and its major and minor grooves; switch DNA for RNA; step out from the helix to nucleosomes on their string.

Explorer

Molecular basis of inheritance

DNA double helix

DNA replication: Watch DNA polymerase copy both strands at the replication fork, one continuously and one in fragments that DNA ligase joins, then follow Meselson and Stahl's heavy, hybrid and light DNA generation by generation.

Mechanism

Molecular basis of inheritance

DNA replication

Transcription: Step RNA polymerase from promoter to terminator along the template strand and watch the RNA grow 5′ to 3′; in a eukaryote, splicing, capping and tailing turn hnRNA into mRNA.

Mechanism

Molecular basis of inheritance

Transcription

Genetic code and translation: Step a ribosome along an mRNA codon by codon and watch the chain of amino acids grow until a stop codon; then change GAG to GUG, or insert one base, and see a point or frameshift mutation.

Mechanism

Molecular basis of inheritance

Genetic code and translation

Lac operon: Add or remove lactose and step the lac operon: the repressor binds the operator or is inactivated by the inducer, and RNA polymerase transcribes z, y and a or is blocked.

Mechanism

Molecular basis of inheritance

Lac operon

Natural selection: Breed a population with a varying trait for generations under stabilising, directional or disruptive selection and watch the distribution move; mutation and recombination feed variation; white-winged and melanised moths on lichen-covered or soot-darkened trunks.

Simulation

Evolution

Natural selection

Hardy-Weinberg principle: Set p and read p², 2pq and q² at equilibrium; then break it generation by generation with gene flow from migrants, genetic drift in a small population, or the founder effect.

Simulation

Evolution

Hardy-Weinberg principle

Biology and human welfare

Biology · Class 12 · 3 labs

Life cycle of Plasmodium: Walk the malarial parasite round its two hosts, from a mosquito bite through liver and red blood cells and back to the salivary glands.

Mechanism

Human health and disease

Life cycle of Plasmodium

Primary and secondary immune response: Plot antibody level against time: a first exposure's slow, small primary response, the fast, large secondary one, a vaccine priming it, and a passive injection that protects at once.

Explorer

Human health and disease

Primary and secondary immune response

HIV and AIDS: Follow HIV into a macrophage or a helper T-lymphocyte as reverse transcriptase makes viral DNA and the cell turns out new viruses.

Mechanism

Human health and disease

HIV and AIDS

Biotechnology and its applications

Biology · Class 12 · 4 labs

Recombinant DNA technology: Step the recombinant DNA process: isolate DNA, cut it with EcoRI, run a gel, amplify, ligate into pBR322, transform a host, select, grow it in a stirred-tank bioreactor and purify downstream, or make human insulin from chains A and B joined by disulphide bridges.

Mechanism

Biotechnology: principles and processes

Recombinant DNA technology

Restriction digestion and gel electrophoresis: Cut DNA with EcoRI at its palindromic GAATTC sites into sticky-ended fragments, run them on an agarose gel and read their sizes; then match VNTR bands to a crime scene or a parent by DNA fingerprinting.

Explorer

Biotechnology: principles and processes

Restriction digestion and gel electrophoresis

Cloning vectors: Ligate foreign DNA into pBR322 or a vector with the β-galactosidase gene; insertional inactivation decides which colonies grow on ampicillin and tetracycline or give no colour; cells take up DNA only once made competent.

Explorer

Biotechnology: principles and processes

Cloning vectors

Polymerase chain reaction: Run PCR cycle by cycle: denature the DNA, anneal the primers and extend them with Taq polymerase, and watch the copies of the gene double every cycle to about a billion after 30.

Simulation

Biotechnology: principles and processes

Polymerase chain reaction

Ecology and environment

Biology · Class 12 · 2 labs

Energy flow and ecological pyramids: Set gross primary productivity and respiration to get net productivity, then pass energy up a food chain at about 10 per cent per level; pyramids of number, biomass and energy draw themselves, with the big tree and the sea as pyramids that are not upright.

Explorer

Ecosystem

Energy flow and ecological pyramids

Species-area relationship: Plot species richness against area on ordinary and log axes (log S = log C + Z log A); Z between 0.1 and 0.2 within a region against 0.6 to 1.2 across continents; latitudinal gradient preset.

Explorer

Biodiversity and conservation