Common intermediate Physics Chemistry Science NCERT
General Science: Physics & Chemistry Basics for PSC Exams
Essential physics and chemistry facts for Kerala PSC — laws of motion, light, sound, electricity, acids-bases-salts, elements, and chemical reactions. Based on NCERT Class 8-10 Science.
Published: 13 Apr 2026 Relevant for: LDC, Last Grade Servants, Graduate Level Prelims
Physics and Chemistry together account for 3-6 questions per Kerala PSC paper. The questions test basic facts and concepts, not calculations. These notes cover the most tested topics from NCERT Class 8-10 Science.
PHYSICS
Newton’s Laws of Motion (NCERT Class 9, Chapter 9)
| Law | Statement | Example |
|---|---|---|
| First Law (Inertia) | A body at rest stays at rest; a body in motion stays in motion — unless acted upon by an external force | Passengers lurch forward when bus brakes suddenly |
| Second Law | Force = Mass × Acceleration (F = ma) | Heavier objects need more force to accelerate |
| Third Law | Every action has an equal and opposite reaction | Rocket propulsion; walking (foot pushes ground, ground pushes back) |
PSC fact: The SI unit of force is Newton (N). 1 Newton = force needed to accelerate 1 kg mass by 1 m/s².
Important SI Units
| Quantity | SI Unit | Symbol |
|---|---|---|
| Length | Metre | m |
| Mass | Kilogram | kg |
| Time | Second | s |
| Temperature | Kelvin | K |
| Electric Current | Ampere | A |
| Force | Newton | N |
| Energy/Work | Joule | J |
| Power | Watt | W |
| Pressure | Pascal | Pa |
| Frequency | Hertz | Hz |
| Electric Potential | Volt | V |
| Resistance | Ohm | Ω |
Light (NCERT Class 10, Chapter 10)
Speed of light: 3 × 10⁸ m/s (in vacuum)
| Concept | Definition | PSC fact |
|---|---|---|
| Reflection | Light bouncing off a surface | Angle of incidence = angle of reflection |
| Refraction | Bending of light when passing between media | Pencil looks bent in water |
| Total Internal Reflection | Light reflected entirely within a denser medium | Optical fibres, mirage |
| Dispersion | White light splitting into 7 colours through prism | VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red) |
Types of lenses:
| Lens | Shape | Image use |
|---|---|---|
| Convex (converging) | Thicker in middle | Magnifying glass, camera, human eye |
| Concave (diverging) | Thinner in middle | Spectacles for myopia (short-sightedness) |
Types of mirrors:
| Mirror | Image | Use |
|---|---|---|
| Concave | Real, inverted (or virtual magnified) | Shaving mirror, headlights, solar furnace |
| Convex | Virtual, erect, diminished | Vehicle rear-view mirror (wider field of view) |
| Plane | Virtual, erect, same size | Regular mirror |
PSC favourites:
- Convex mirror used in: Rear-view mirrors (because it gives a wider field of view)
- Concave mirror used in: Headlights, torch, solar cooker
- Defect corrected by concave lens: Myopia (near-sightedness)
- Defect corrected by convex lens: Hypermetropia (far-sightedness)
Sound (NCERT Class 9, Chapter 12)
| Fact | Detail |
|---|---|
| Speed in air | ~343 m/s (at 20°C) |
| Speed in water | ~1,480 m/s |
| Speed in steel | ~5,960 m/s |
| Travels fastest in | Solids > Liquids > Gases |
| Cannot travel through | Vacuum (needs a medium) |
| Frequency unit | Hertz (Hz) |
| Human hearing range | 20 Hz to 20,000 Hz |
| Below 20 Hz | Infrasound (elephants, earthquakes) |
| Above 20,000 Hz | Ultrasound (bats, dolphins, medical scans) |
| Echo | Reflected sound; needs minimum 17.2 m distance |
PSC trap: Sound travels fastest in solids, not gases. Many students think “air” because we hear through air. Also: sound CANNOT travel through vacuum — that’s why there’s no sound in space.
Electricity (NCERT Class 10, Chapter 12)
Ohm’s Law: V = IR (Voltage = Current × Resistance)
| Quantity | Unit | Instrument |
|---|---|---|
| Current (I) | Ampere (A) | Ammeter |
| Voltage (V) | Volt (V) | Voltmeter |
| Resistance (R) | Ohm (Ω) | Ohmmeter |
| Power (P) | Watt (W) | P = VI |
Electric power: P = VI = I²R = V²/R 1 unit of electricity = 1 kWh = 1000 Watt × 1 hour
Series vs Parallel:
| Feature | Series Circuit | Parallel Circuit |
|---|---|---|
| Current | Same through all | Divides |
| Voltage | Divides | Same across all |
| Total resistance | R₁ + R₂ + R₃ | 1/R = 1/R₁ + 1/R₂ |
| If one bulb fails | All go off | Others remain on |
| Home wiring | Not used | Used in homes |
Magnetism
| Fact | Detail |
|---|---|
| Earth behaves as | A giant magnet (geomagnetic field) |
| Magnetic compass | North-seeking pole points to geographic North |
| Electromagnet | Made by winding wire around iron core and passing current |
| Uses of electromagnet | Electric bells, MRI machines, maglev trains, speakers |
| Permanent magnets | Cannot be turned off; made from iron, cobalt, nickel |
CHEMISTRY
Acids, Bases, and Salts (NCERT Class 10, Chapter 2)
pH Scale: 0 (strongly acidic) → 7 (neutral) → 14 (strongly basic/alkaline)
| Substance | pH | Nature |
|---|---|---|
| Stomach acid (HCl) | ~1-2 | Strongly acidic |
| Lemon juice | ~2-3 | Acidic |
| Vinegar | ~3 | Acidic |
| Pure water | 7 | Neutral |
| Blood | ~7.4 | Slightly alkaline |
| Baking soda | ~8-9 | Alkaline |
| Milk of magnesia | ~10 | Alkaline |
| Bleach | ~12-13 | Strongly alkaline |
Important Chemical Compounds
| Common name | Chemical name | Formula | Use |
|---|---|---|---|
| Common salt | Sodium Chloride | NaCl | Cooking, preservation |
| Baking soda | Sodium Bicarbonate | NaHCO₃ | Cooking, antacid, fire extinguisher |
| Washing soda | Sodium Carbonate | Na₂CO₃ | Cleaning, water softening |
| Caustic soda | Sodium Hydroxide | NaOH | Soap making, paper |
| Lime | Calcium Oxide | CaO | Whitewash, cement |
| Slaked lime | Calcium Hydroxide | Ca(OH)₂ | Whitewashing |
| Limestone/Marble | Calcium Carbonate | CaCO₃ | Construction, cement |
| Plaster of Paris | Calcium Sulphate Hemihydrate | CaSO₄·½H₂O | Casts, moulds, surgery |
| Blue vitriol | Copper Sulphate | CuSO₄·5H₂O | Electroplating, agriculture |
| Bleaching powder | Calcium Hypochlorite | Ca(OCl)₂ | Water purification, bleaching |
| Dry ice | Solid Carbon Dioxide | CO₂ (solid) | Refrigeration (sublimes, doesn’t melt) |
Top PSC chemistry questions:
- Baking soda formula: NaHCO₃
- Washing soda formula: Na₂CO₃
- pH of pure water: 7
- pH of blood: ~7.4
- Dry ice is: Solid CO₂
- Plaster of Paris is: CaSO₄·½H₂O
Elements and Periodic Table Basics
| Fact | Detail |
|---|---|
| Total known elements | 118 (as of 2024) |
| Most abundant in Universe | Hydrogen |
| Most abundant in Earth’s crust | Oxygen (~46%) |
| Most abundant metal in crust | Aluminium |
| Lightest element | Hydrogen |
| Heaviest natural element | Uranium |
| Liquid metal at room temp | Mercury (Hg) |
| Liquid non-metal at room temp | Bromine (Br) |
| Hardest natural substance | Diamond (form of Carbon) |
| Best conductor of electricity | Silver (Ag) |
| Most ductile metal | Gold (Au) |
| Periodic table inventor | Dmitri Mendeleev (1869) |
Important Chemical Reactions
| Reaction | Example |
|---|---|
| Rusting | Iron + Oxygen + Water → Iron Oxide (rust) — Fe₂O₃ |
| Photosynthesis | 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight + chlorophyll) |
| Respiration | C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy |
| Fermentation | Sugar → Alcohol + CO₂ (by yeast; anaerobic) |
| Neutralisation | Acid + Base → Salt + Water |
Metals and Non-metals (NCERT Class 10, Chapter 3)
| Property | Metals | Non-metals |
|---|---|---|
| State | Mostly solid (except Mercury) | Solid, liquid, or gas |
| Lustre | Shiny | Dull |
| Malleability | Can be hammered into sheets | Brittle |
| Ductility | Can be drawn into wires | Cannot |
| Conductivity | Good conductors | Poor conductors (except Graphite) |
| Sound | Sonorous (ring when struck) | Non-sonorous |
| Electron tendency | Lose electrons (form +ve ions) | Gain electrons (form -ve ions) |
PSC exceptions to remember:
- Mercury = metal but liquid at room temperature
- Graphite = non-metal but conducts electricity
- Diamond = hardest but is just a form of carbon (non-metal)
- Iodine = non-metal but has lustre (shiny)
Gases and Their Uses
| Gas | Formula | Key property/use |
|---|---|---|
| Oxygen | O₂ | Respiration, combustion; Joseph Priestley discovered |
| Nitrogen | N₂ | 78% of air; used in fertilizers, food preservation |
| Carbon Dioxide | CO₂ | Greenhouse gas; used in fire extinguishers, carbonated drinks |
| Ozone | O₃ | Protects from UV rays; CFCs destroy it |
| Hydrogen | H₂ | Lightest gas; used in rocket fuel |
| Methane | CH₄ | Main component of natural gas and biogas |
| Carbon Monoxide | CO | Poisonous; produced by incomplete combustion |
| Chlorine | Cl₂ | Water purification; bleaching |
| Ammonia | NH₃ | Fertilizers; refrigeration |
| Laughing Gas | N₂O | Anaesthesia (nitrous oxide) |
| Tear Gas | Various | Used for crowd control |
Quick Revision — 25 Most Asked Physics & Chemistry Questions
- SI unit of force: Newton
- SI unit of energy: Joule
- SI unit of power: Watt
- Speed of light: 3 × 10⁸ m/s
- Speed of sound in air: ~343 m/s
- Sound travels fastest in: Solids
- Sound cannot travel through: Vacuum
- Ohm’s Law: V = IR
- Mirror used in vehicles: Convex mirror
- Lens for myopia: Concave lens
- Lens for hypermetropia: Convex lens
- VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red
- Human hearing range: 20 Hz to 20,000 Hz
- pH of pure water: 7
- pH of blood: ~7.4
- Baking soda: NaHCO₃ (Sodium Bicarbonate)
- Washing soda: Na₂CO₃ (Sodium Carbonate)
- Liquid metal: Mercury
- Most abundant element in crust: Oxygen
- Most abundant metal in crust: Aluminium
- Hardest substance: Diamond
- Dry ice: Solid CO₂
- Laughing gas: N₂O (Nitrous Oxide)
- Rusting is: Oxidation of iron
- Best conductor of electricity: Silver
Notes based on NCERT Class 8 Science (Ch. 4, 14, 15), Class 9 Science (Ch. 8, 9, 12), Class 10 Science (Ch. 1, 2, 3, 10, 12). Updated April 2026.