For Class 8, 9 & 10
Master the basics - and everything after gets easier
Concept-first questions with clear model answers in Physics, Chemistry, Maths and Biology, all NCERT-aligned. Start early, build the habit, and walk into your boards, NEET and JEE already ahead.
Interactive lessons
learn by playingDrag, slide and build - watch each concept come alive, then reveal the answer.
200 interactive lessons
Ohm's law
Class 10 Physics
Slide V & R, watch the bulb glow
Open →pH scale
Class 10 Chemistry
Slide across acids and bases
Open →Atomic number and mass number
Class 9 Chemistry
Add protons & neutrons, build shells
Open →Laws of reflection
Class 8 Physics
Change the angle, watch it bounce
Open →Volume of a sphere
Class 9 Maths
Grow the radius, see the volume
Open →Area of a trapezium
Class 8 Maths
Drag the sides, read the area
Open →Power of a lens
Class 10 Physics
Move the object, trace the rays
Open →Food chain and energy flow
Class 10 Biology
Follow the energy as it flows
Open →Speed
Class 8 Physics
Slide distance & time, watch the speed
Open →Density
Class 9 Physics
Pack mass into volume, float or sink
Open →Work done
Class 9 Physics
Push harder or farther, watch work grow
Open →Kinetic energy
Class 9 Physics
Speed it up - energy grows with the square
Open →Power of a lens
Class 10 Physics
Shorten the focal length, boost the power
Open →Mole concept
Class 9 Chemistry
Weigh out grams, count the moles
Open →Avogadro's number
Class 9 Chemistry
Add moles, count the particles
Open →Microscope magnification
Class 8 Biology
Grow the image, read the magnification
Open →Population density
Class 10 Biology
Add individuals, shrink the land, see crowding
Open →Simple interest
Class 8 Maths
Slide money, rate & time, watch interest
Open →Pythagoras theorem
Class 9 Maths
Stretch the two sides, get the hypotenuse
Open →Probability of an event
Class 10 Maths
Change the outcomes, watch the odds
Open →Newton's second law
Class 9 Physics
Push a mass, pick an acceleration
Open →Momentum
Class 9 Physics
Slide mass & velocity, build momentum
Open →Pressure
Class 8 Physics
Shrink the area, feel the pressure rise
Open →Weight
Class 9 Physics
Change the planet's gravity, watch your weight
Open →Refractive index
Class 10 Physics
Slow light in the medium, raise the index
Open →Resistors in series
Class 10 Physics
Add two resistors in a line
Open →Mass percentage of a solution
Class 9 Chemistry
Dissolve solute, read the strength
Open →Concentration of a solution
Class 9 Chemistry
Pack solute into less liquid
Open →Population change
Class 10 Biology
Balance births against deaths
Open →Compound microscope
Class 8 Biology
Combine eyepiece & objective lenses
Open →Area of a circle
Class 8 Maths
Grow the radius, watch the area square
Open →Volume of a cuboid
Class 8 Maths
Stretch length, breadth & height
Open →Electronic configuration and valency
Class 9 Chemistry
Slide the atomic number, build the atom
Open →Homologous series (alkanes)
Class 10 Chemistry
Add carbons, name the compound
Open →Mass number
Class 9 Chemistry
Add protons & neutrons, get the mass number
Open →Power
Class 9 Physics
More work in less time = more power
Open →Potential energy
Class 9 Physics
Lift a mass higher, store energy
Open →Wave speed
Class 9 Physics
Tune frequency & wavelength, set the speed
Open →Electric current
Class 10 Physics
Push charge per second, get the current
Open →Percentage
Class 8 Maths
Compare part to whole as a %
Open →Electron dot structure
Class 9 Chemistry
Draw valence electrons as dots
Open →Acceleration
Class 9 Physics
Speed up over time, find acceleration
Open →Distance, speed and time
Class 8 Physics
Set speed & time, cover the distance
Open →Frequency and time period
Class 9 Physics
Shorten the period, raise the frequency
Open →Heating effect of current
Class 10 Physics
Raise the current, watch heating soar
Open →Area of a triangle
Class 8 Maths
Set base & height, halve the rectangle
Open →Area of a rectangle
Class 8 Maths
Set length & breadth, fill the area
Open →Mean (average)
Class 9 Maths
Share the total equally across items
Open →Discount
Class 8 Maths
Slide price & % off, see the saving
Open →Heart rate
Class 10 Biology
Set heart rate & time, count the beats
Open →Resistors in parallel
Class 10 Physics
Wire two resistors side by side
Open →Electric charge
Class 10 Physics
Flow current over time, collect charge
Open →Electrical energy and units
Class 10 Physics
Run appliances, add up the units
Open →Kelvin temperature scale
Class 9 Chemistry
Slide Celsius, read the Kelvin
Open →Moles from number of particles
Class 9 Chemistry
Divide particles by Avogadro's number
Open →Ten percent law
Class 10 Biology
See 10% of energy reach the next level
Open →Area of a square
Class 8 Maths
Grow the side, square the area
Open →Volume of a cube
Class 8 Maths
Grow the edge, cube the volume
Open →Circumference of a circle
Class 8 Maths
Grow the radius, roll out the rim
Open →Surface area of a cube
Class 9 Maths
Grow the edge, cover six faces
Open →Potential difference
Class 10 Physics
Share work across charge, get volts
Open →Resistance from Ohm's law
Class 10 Physics
Divide voltage by current, get resistance
Open →Echo and SONAR
Class 9 Physics
Time the echo, find the distance
Open →Mass from moles
Class 9 Chemistry
Multiply moles by molar mass
Open →Breathing rate
Class 10 Biology
Set breathing rate & time
Open →Volume of a cylinder
Class 10 Maths
Set radius & height, fill the can
Open →Compound interest
Class 8 Maths
Compound money over years
Open →Profit and loss percentage
Class 8 Maths
Set cost & selling price, see profit %
Open →Perimeter of a rectangle
Class 8 Maths
Set length & breadth, walk the border
Open →Surface area of a sphere
Class 10 Maths
Grow the radius, wrap the ball
Open →Time period
Class 9 Physics
Raise the frequency, shrink the period
Open →Relative velocity
Class 9 Physics
Two objects approach - add their speeds
Open →Average velocity
Class 9 Physics
Average the start and end speeds
Open →Equations of motion (v = u + at)
Class 9 Physics
Accelerate from u for a time t
Open →Kelvin to Celsius
Class 9 Chemistry
Slide Kelvin, read the Celsius
Open →Population growth rate
Class 10 Biology
Balance births vs deaths per population
Open →Perimeter of a square
Class 8 Maths
Grow the side, walk four edges
Open →Perimeter of a triangle
Class 8 Maths
Add the three sides
Open →Area of a parallelogram
Class 8 Maths
Set base & height, slide the shape
Open →Area of a rhombus
Class 8 Maths
Set the two diagonals
Open →Equations of motion (distance)
Class 9 Physics
Start, accelerate, cover ground
Open →Joule's law of heating
Class 10 Physics
Raise current, resistance or time
Open →Electric power (P = VI)
Class 10 Physics
Multiply voltage by current
Open →Average atomic mass of isotopes
Class 9 Chemistry
Mix two isotopes by abundance
Open →Seed germination percentage
Class 9 Biology
Count sprouted seeds out of the total
Open →Volume of a cone
Class 9 Maths
Set radius & height, fill the cone
Open →Surface area of a cylinder
Class 9 Maths
Wrap the side and both ends
Open →Surface area of a cuboid
Class 9 Maths
Cover all six rectangular faces
Open →nth term of an AP
Class 10 Maths
Step from the first term by d
Open →Sum of an AP
Class 10 Maths
Add up the first n terms
Open →Focal length of a mirror
Class 10 Physics
Halve the radius to find the focus
Open →Speed of light in a medium
Class 10 Physics
Raise the index, slow the light
Open →Percentage purity
Class 9 Chemistry
Weigh the pure part of a sample
Open →Slope of a line
Class 10 Maths
Rise over run gives the steepness
Open →Percentage change
Class 8 Maths
Compare a new value to the old
Open →Volume of a hemisphere
Class 9 Maths
Grow the radius of half a ball
Open →Area of a sector
Class 10 Maths
Cut a slice of angle from a circle
Open →Length of an arc
Class 10 Maths
Measure the curved edge of a slice
Open →Slant height of a cone
Class 9 Maths
Combine radius & height for the slant
Open →Unit conversion (km/h to m/s)
Class 9 Physics
Convert km/h into m/s
Open →Equations of motion (v^2 = u^2 + 2as)
Class 9 Physics
Accelerate over a distance, find v
Open →Impulse
Class 9 Physics
Hit harder or longer, change momentum
Open →Wavelength
Class 9 Physics
Speed over frequency gives wavelength
Open →Oscillations
Class 9 Physics
Vibrate at a frequency for a time
Open →Cost of electricity
Class 10 Physics
Units times rate gives the bill
Open →Number of neutrons
Class 9 Chemistry
Take protons away from the mass number
Open →Curved surface area of a cone
Class 9 Maths
Wrap the slanted side of a cone
Open →Total surface area of a cone
Class 9 Maths
Add the base circle to the cone's side
Open →Curved surface area of a hemisphere
Class 9 Maths
Cover the dome of a hemisphere
Open →Diagonal of a square
Class 9 Maths
Cross a square corner to corner
Open →Unit conversion (m/s to km/h)
Class 9 Physics
Convert m/s into km/h
Open →Distance from velocities
Class 9 Physics
From two speeds, find the distance
Open →Diagonal of a rectangle
Class 9 Maths
Cross a rectangle corner to corner
Open →Diagonal of a cuboid
Class 9 Maths
The longest rod that fits in a box
Open →Area by Heron's formula
Class 9 Maths
Area from just the three sides
Open →Interior angle sum of a polygon
Class 8 Maths
Add up a polygon's inside angles
Open →Exterior angle of a regular polygon
Class 8 Maths
Share 360 among a polygon's corners
Open →Number of diagonals of a polygon
Class 8 Maths
Count the diagonals of a polygon
Open →Discriminant
Class 10 Maths
Test how many roots a quadratic has
Open →Sum of roots
Class 10 Maths
Sum of a quadratic's roots
Open →Punnett square (monohybrid cross)
Class 10 Biology
Cross two parents, predict the offspring
Open →Balancing chemical equations
Class 10 Chemistry
Slide coefficients until atoms balance
Open →Writing chemical formulae (valency)
Class 9 Chemistry
Criss-cross valencies into a formula
Open →Current from power
Class 10 Physics
Divide power by voltage for current
Open →Power (P = V^2 / R)
Class 10 Physics
Voltage squared over resistance
Open →Sine ratio
Class 10 Maths
Opposite over hypotenuse
Open →Cosine ratio
Class 10 Maths
Adjacent over hypotenuse
Open →Tangent ratio
Class 10 Maths
Opposite over adjacent
Open →Area of an equilateral triangle
Class 9 Maths
Area of an equilateral triangle
Open →Curved surface area of a cylinder
Class 9 Maths
Wrap only the curved side
Open →Loss percentage
Class 8 Maths
Sell below cost, find the loss %
Open →Amount with simple interest
Class 8 Maths
Principal plus its simple interest
Open →Distance formula
Class 10 Maths
Straight distance between two points
Open →States of matter
Class 9 Chemistry
Heat particles solid → liquid → gas
Open →Parts of a plant cell
Class 8 Biology
Tap a cell part to see its job
Open →Diagonal of a cube
Class 9 Maths
Longest diagonal through a cube
Open →Total surface area of a hemisphere
Class 9 Maths
Dome plus its flat circle
Open →Sum of first n natural numbers
Class 10 Maths
Add 1 + 2 + ... + n instantly
Open →Range of data
Class 9 Maths
Spread from smallest to largest
Open →Class mark
Class 9 Maths
Midpoint of a class interval
Open →Selling price from profit percent
Class 8 Maths
Mark up cost by a profit %
Open →Perimeter of a sector
Class 10 Maths
Two radii plus the curved arc
Open →Circumference from diameter
Class 8 Maths
Circumference straight from diameter
Open →Power (P = F x v)
Class 9 Physics
Force times velocity gives power
Open →Percentage of a number
Class 8 Maths
Find a percentage of a number
Open →Series and parallel circuits
Class 10 Physics
Break a bulb in series vs parallel
Open →Symbols of elements
Class 9 Chemistry
Match each element to its symbol
Open →Free fall (velocity)
Class 9 Physics
Drop from a height, hit this speed
Open →Free fall (time)
Class 9 Physics
How long a drop takes
Open →Free fall (distance)
Class 9 Physics
Distance fallen in a given time
Open →Complement of an event
Class 10 Maths
Chance an event does NOT happen
Open →Product of roots
Class 10 Maths
Product of a quadratic's roots
Open →Exterior angle theorem
Class 9 Maths
Exterior angle = sum of remote interiors
Open →Complementary angles
Class 10 Maths
What adds to 90 degrees
Open →Supplementary angles
Class 9 Maths
What adds to 180 degrees
Open →Perimeter of a semicircle
Class 10 Maths
Curved half plus the diameter
Open →Area of a semicircle
Class 10 Maths
Half the area of a circle
Open →Turning effect (moments)
Class 9 Physics
Balance the see-saw with moments
Open →Reflex arc
Class 10 Biology
Step through a reflex, stimulus to action
Open →Buoyant force (upthrust)
Class 9 Physics
Displace liquid, feel the upthrust
Open →Relative density
Class 9 Physics
Compare a density to water's
Open →Power in lifting a load
Class 9 Physics
Lift a load, faster needs more power
Open →Cosecant ratio
Class 10 Maths
Hypotenuse over opposite
Open →Secant ratio
Class 10 Maths
Hypotenuse over adjacent
Open →Cotangent ratio
Class 10 Maths
Adjacent over opposite
Open →Height from angle of elevation
Class 10 Maths
Height from an angle of elevation
Open →Area of a quadrant
Class 10 Maths
A quarter of a circle's area
Open →Interior angle of a regular polygon
Class 8 Maths
One inside angle of a regular polygon
Open →Sum of first n odd numbers
Class 10 Maths
Add the first n odd numbers
Open →Sum of first n even numbers
Class 10 Maths
Add the first n even numbers
Open →Quadratic formula (a root)
Class 10 Maths
Larger root of a quadratic
Open →LCM from HCF
Class 10 Maths
LCM from the product and HCF
Open →Depreciation
Class 8 Maths
Value drops by a % each year
Open →Cost price from selling price
Class 8 Maths
Work back to the cost price
Open →Downstream speed
Class 8 Maths
Row with the current
Open →Upstream speed
Class 8 Maths
Row against the current
Open →Average speed for a round trip
Class 8 Maths
Average speed there and back
Open →Sales tax / GST
Class 8 Maths
Tax added on a price
Open →Area of a ring (annulus)
Class 10 Maths
Area of a ring between two circles
Open →Edge of a cube from volume
Class 9 Maths
Edge back from the volume
Open →Radius from area
Class 10 Maths
Radius back from a circle's area
Open →Side from area of a square
Class 8 Maths
Side back from a square's area
Open →Height of a triangle from area
Class 9 Maths
Height back from area and base
Open →Rate from simple interest
Class 8 Maths
Rate back from the interest
Open →Time from simple interest
Class 8 Maths
Time back from the interest
Open →Principal from simple interest
Class 8 Maths
Principal back from the interest
Open →Mean proportional
Class 10 Maths
Geometric mean of two numbers
Open →Fourth proportional
Class 8 Maths
Complete the proportion a : b = c : ?
Open →Marked price from selling price
Class 8 Maths
Marked price back from the sale price
Open →Chambers of the human heart
Class 10 Biology
Tap a heart chamber to see its job
Open →Equation of a line (y = mx + c)
Class 9 Maths
Read y off a straight line
Open →Average term of an AP
Class 10 Maths
Average of first and last term
Open →Number of terms in an AP
Class 10 Maths
How many terms in an AP
Open →Midpoint of two points
Class 10 Maths
x-coordinate of a midpoint
Open →Empirical mode
Class 10 Maths
Estimate the mode from mean & median
Open →Length of a shadow
Class 10 Maths
Shadow from height and sun angle
Open →Train crossing a pole
Class 8 Maths
Speed to cross a pole
Open →Time and work
Class 8 Maths
More workers, fewer days
Open →Dividing in a ratio
Class 8 Maths
Split a total in a ratio
Open →Unitary method
Class 8 Maths
Cost of a single item
Open →Your progress — Foundation - Class 8 to 10
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Showing 9 questions in Chemistry for Class 10. Tap a card to reveal the answer.
ChemistryCarbon and its CompoundsmediumWhy does carbon form a very large number of compounds?
Reveal answer ↓
What it is
Carbon forms millions of compounds because it makes four strong covalent bonds and chains (catenation).
Answer
Carbon has four valence electrons, so it shares electrons to form four strong covalent bonds rather than gaining or losing electrons. Two special properties help: catenation (carbon atoms link with other carbon atoms to form long chains, branches and rings) and tetravalency (it can bond with four other atoms such as hydrogen, oxygen, nitrogen). Together these give a huge number of stable compounds.
Carbon valency = 4 (forms 4 covalent bonds)
- •4 valence electrons -> 4 covalent bonds
- •Catenation: C-C chains, branches, rings
- •Tetravalency allows bonding with many elements
- •Small size -> strong stable bonds
Why learn this
It's why all life, fuels, plastics and medicines are carbon-based - the reason 'organic' chemistry exists.
💡 Memory trick
Carbon's superpowers: Tetravalency (4 bonds) + Catenation (C-C chains).
ChemistryCarbon and its CompoundsmediumWhat is a homologous series? State two of its characteristics.
Reveal answer ↓
What it is
A homologous series is a family of carbon compounds with the same general formula, differing by CH2.
Answer
A homologous series is a group of organic compounds having the same general formula and the same functional group, in which each successive member differs from the previous one by a -CH2- unit. Two characteristics are: (1) all members have similar chemical properties because of the same functional group, and (2) their physical properties such as boiling point change gradually as the molecule gets bigger. The alkanes (CH4, C2H6, C3H8, ...) are an example.
Successive members differ by CH2
- •Same general formula and functional group
- •Successive members differ by -CH2-
- •Similar chemical properties; gradual change in physical properties
- •Example: alkanes
Why learn this
It lets chemists predict the properties of thousands of organic compounds from one pattern.
💡 Memory trick
Each member differs by CH2; same functional group, gradually changing physical properties.
ChemistryCarbon and its CompoundsmediumWhy does carbon form a very large number of compounds?
Reveal answer ↓
What it is
Carbon forms millions of compounds because of catenation and its tetravalency.
Answer
Carbon forms an extremely large number of compounds for two main reasons. First, catenation: carbon atoms can form strong covalent bonds with other carbon atoms, creating long straight chains, branched chains and rings. Second, tetravalency: a carbon atom has four valence electrons, so it can form four strong covalent bonds with other atoms such as hydrogen, oxygen, nitrogen, sulphur and the halogens. Together these give a huge variety of stable molecules.
Catenation + tetravalency (valency of carbon = 4)
- •Catenation: carbon-carbon chains, branches and rings
- •Tetravalency: forms four covalent bonds
- •Carbon-carbon bonds are strong and stable
- •Leads to millions of organic compounds
Why learn this
It is why all living things, fuels, plastics and medicines are built on carbon.
💡 Memory trick
Carbon has 4 bonds (tetravalent) and links to more carbons (catenation) -> endless chains and rings.
ChemistryCarbon and its CompoundsmediumHow are alkanes named as the carbon chain grows? Slide the number of carbon atoms to explore.
Reveal answer ↓
What it is
Alkanes form a homologous series of saturated hydrocarbons with the general formula CnH(2n+2).
C3H8
Propane
3 carbons in a chain, single bonds only (saturated)
Every alkane fits CₙH₂ₙ₊₂. Each step up the series adds one CH₂ unit - a homologous series.
Answer
Alkanes are saturated hydrocarbons (only single C-C and C-H bonds) with the general formula CnH(2n+2), where n is the number of carbon atoms. So n = 1 gives CH4 (methane), n = 2 gives C2H6 (ethane), n = 3 gives C3H8 (propane) and n = 4 gives C4H10 (butane). Each successive member differs by one CH2 unit - this family is called a homologous series.
alkane: CnH(2n+2)
- •General formula: CnH(2n+2)
- •Saturated - only single bonds
- •Consecutive members differ by CH2
- •1 methane, 2 ethane, 3 propane, 4 butane, 5 pentane
Why learn this
It shows how a whole family of fuels (methane, LPG, petrol) is built by adding one carbon at a time.
💡 Memory trick
Alkane = CnH(2n+2). n = 1 methane, 2 ethane, 3 propane, 4 butane ...
ChemistryCarbon and its CompoundsmediumWhy does carbon form a very large number of compounds?
Reveal answer ↓
What it is
Carbon forms covalent bonds by sharing electrons, and its properties of catenation and tetravalency let it form a huge number of compounds.
Answer
Carbon forms a very large number of compounds mainly for two reasons. First, catenation: carbon atoms have a strong ability to bond with other carbon atoms to form long chains, branched chains and rings. Second, tetravalency: a carbon atom has four valence electrons, so it can form four strong covalent bonds by sharing electrons with other carbon atoms or with atoms of other elements such as hydrogen, oxygen, nitrogen and the halogens. These bonds are strong and stable, giving a vast variety of compounds.
- •Carbon forms covalent bonds by sharing electrons
- •Catenation: carbon bonds to carbon (chains, rings)
- •Tetravalency: forms four bonds
- •Together they give millions of compounds
Why learn this
It is why carbon is the basis of all life and organic chemistry.
💡 Memory trick
Carbon: 4 bonds (tetravalent) + can bond to itself endlessly (catenation) = millions of compounds.
ChemistryCarbon and its CompoundsmediumDifferentiate between saturated and unsaturated hydrocarbons with examples.
Reveal answer ↓
What it is
Saturated hydrocarbons (alkanes) have only single carbon-carbon bonds; unsaturated hydrocarbons (alkenes, alkynes) have double or triple bonds.
Answer
Saturated hydrocarbons, called alkanes, contain only single covalent bonds between carbon atoms and hold the maximum number of hydrogen atoms; they are relatively unreactive and burn with a clean blue flame, for example methane (CH4) and ethane (C2H6). Unsaturated hydrocarbons contain at least one carbon-carbon double bond (alkenes, such as ethene C2H4) or triple bond (alkynes, such as ethyne C2H2); they are more reactive, undergo addition reactions, and burn with a sooty yellow flame.
Alkane CnH2n+2 ; Alkene CnH2n ; Alkyne CnH2n-2
- •Saturated (alkanes): only single bonds (CH4, C2H6)
- •Unsaturated: double bond (alkenes) or triple bond (alkynes)
- •Saturated burn with a clean blue flame
- •Unsaturated are more reactive, sooty flame
Why learn this
The type of bond decides how a hydrocarbon reacts and burns.
💡 Memory trick
Alkane = single bonds (saturated). Alkene = double, Alkyne = triple (both unsaturated).
ChemistryCarbon and its CompoundsmediumWhat is a homologous series? State two of its characteristics.
Reveal answer ↓
What it is
A homologous series is a family of compounds with the same functional group and general formula, differing by CH2.
Answer
A homologous series is a group (family) of organic compounds having the same general formula and the same functional group, in which each successive member differs from the previous one by a -CH2- unit. Its characteristics are: all members have the same functional group and hence similar chemical properties; consecutive members differ by a CH2 group (a mass difference of 14 units); and their physical properties, such as melting and boiling points, change gradually with increasing molecular mass. Examples include the alkanes and the alcohols.
Successive members differ by CH2 (14 u)
- •Same functional group and general formula
- •Successive members differ by CH2
- •Similar chemical properties
- •Physical properties change gradually
Why learn this
It lets us predict the properties of a whole family from one member.
💡 Memory trick
Consecutive members differ by CH2 (mass 14) and share the same functional group.
ChemistryCarbon and its CompoundsmediumGive the functional group and one property each of ethanol and ethanoic acid.
Reveal answer ↓
What it is
Ethanol (C2H5OH) is an alcohol and ethanoic acid (CH3COOH) is a carboxylic acid; they have distinct properties and uses.
Answer
Ethanol (C2H5OH) contains the alcohol functional group -OH; it is a colourless liquid used as a solvent, in sanitisers and in alcoholic drinks, and it reacts with sodium to release hydrogen. Ethanoic acid (CH3COOH), commonly known as acetic acid, contains the carboxylic acid functional group -COOH; its dilute solution is called vinegar, it has a sour taste and pungent smell, turns blue litmus red, and reacts with sodium carbonate to give carbon dioxide. Ethanol and ethanoic acid react together (esterification) to form a sweet-smelling ester.
C2H5OH (ethanol) ; CH3COOH (ethanoic acid)
- •Ethanol: -OH group, used in sanitisers and drinks
- •Ethanoic acid: -COOH group (vinegar)
- •Ethanoic acid turns blue litmus red
- •Ethanol + acid -> ester (esterification)
Why learn this
Ethanol is in alcoholic drinks and sanitisers; ethanoic acid is the main part of vinegar.
💡 Memory trick
Ethanol = -OH group (alcohol). Ethanoic acid = -COOH group (vinegar smell).
ChemistryCarbon and its CompoundshardWhat is a micelle? How do soaps remove oily dirt?
Reveal answer ↓
What it is
Soaps and detergents clean by forming micelles that trap oily dirt so it can be washed away in water.
Answer
A soap molecule has two ends: a long hydrocarbon tail that is hydrophobic (water-repelling but oil-attracting) and an ionic head that is hydrophilic (water-attracting). When soap is added to water containing oily dirt, the hydrophobic tails attach to the oil droplet while the hydrophilic heads point outward into the water, forming a spherical cluster called a micelle. This traps the oily dirt inside, keeps it suspended in water, and it is then rinsed away. Detergents work similarly but also clean well in hard water.
- •Soap has a hydrophobic tail and hydrophilic head
- •Tails surround the oil droplet
- •Heads point into water, forming a micelle
- •Detergents also work in hard water
Why learn this
It explains how cleaning agents remove greasy dirt that water alone cannot.
💡 Memory trick
A soap molecule has a water-loving head and an oil-loving tail; tails trap grease -> micelle.
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