Punjab PSEB Matric Science cheat sheet

pH below 7 is acidic, exactly 7 is neutral and above 7 is basic at 25 °C; pH = −log[H⁺], so a change of one pH unit means a tenfold change in hydrogen-ion concentration.

Acids release H⁺ (as H₃O⁺) in water, turn blue litmus red and give CO₂ with metal carbonates; bases release OH⁻, turn red litmus blue and feel soapy to touch.

Neutralisation: acid + base → salt + water (HCl + NaOH → NaCl + H₂O); metal + dilute acid → salt + hydrogen (Zn + H₂SO₄ → ZnSO₄ + H₂).

Salts to memorise: baking soda NaHCO₃, washing soda Na₂CO₃·10H₂O, bleaching powder Ca(OCl)Cl, plaster of Paris CaSO₄·½H₂O, gypsum CaSO₄·2H₂O.

Chlor-alkali process: electrolysis of concentrated brine gives NaOH in solution, Cl₂ at the anode and H₂ at the cathode.

Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au; metals above hydrogen displace it from dilute acids, metals below do not.

Alloys: brass = Cu + Zn, bronze = Cu + Sn, solder = Pb + Sn (low melting point), steel = Fe + C; alloying usually raises hardness and lowers electrical conductivity.

Carbon allotropes: diamond is sp³ bonded in 3-D, hardest natural substance, non-conductor; graphite is sp² layers with delocalised electrons, conducts and is slippery; fullerene is the C₆₀ cage.

Ethanol C₂H₅OH + ethanoic acid CH₃COOH, warmed with a little acid catalyst, gives ethyl ethanoate, a sweet-smelling ester; dilute ethanoic acid (vinegar) is a weak acid of pH about 3.

Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ in chloroplasts using chlorophyll and sunlight; stomata let CO₂ in and O₂ out and are opened by turgid guard cells.

Digestion: salivary amylase converts starch to maltose at near-neutral pH; pepsin acts on proteins in the acidic stomach; trypsin and lipase act in the small intestine.

Aerobic respiration in mitochondria releases far more energy per glucose than anaerobic; anaerobic products are lactic acid in muscles and ethanol + CO₂ in yeast.

Human transport is a double circulation; RBCs carry oxygen on haemoglobin, platelets clot blood, and the nephron is the functional unit of the kidney.

Nerve impulses pass dendrite → cell body → axon → synapse; reflex arcs relay in the spinal cord for fast involuntary responses; cerebrum handles thinking, cerebellum balance and precision, medulla involuntary actions.

Plant hormones: auxin - phototropism and cell elongation; gibberellin - stem elongation; cytokinin - cell division; abscisic acid - dormancy and stomatal closure.

Human hormones: insulin (pancreas, lowers blood glucose), thyroxine (thyroid, requires iodine), adrenaline (fight-or-flight), growth hormone (pituitary).

Mendel's ratios: monohybrid F₂ is 3:1 phenotypically and 1:2:1 genotypically; dihybrid F₂ is 9:3:3:1; human females are XX and males XY, so the father determines sex.

Evolution evidence: fossils, homologous organs (same basic structure, different function - divergent evolution) versus analogous organs (different structure, same function - convergent evolution).

Reflection: angle of incidence = angle of reflection, with incident ray, normal and reflected ray in one plane; a plane mirror gives a virtual, erect, laterally inverted image at the same distance behind as the object is in front.

Spherical mirrors: 1/v + 1/u = 1/f, m = −v/u = h′/h, R = 2f; a concave mirror gives real inverted images for objects beyond F, while a convex mirror always gives virtual, diminished images.

Sign convention: distances are measured from the pole, positive along the direction of the incident light; f is negative for a concave mirror and positive for a convex mirror.

Refraction: sin i / sin r = n₂₁ = v₁/v₂; absolute refractive index n = c/v, with water 1.33, glass about 1.5 and diamond 2.42; light bends towards the normal going from rarer to denser medium.

Total internal reflection occurs when light travels from denser to rarer medium at an angle greater than the critical angle; it explains the sparkle of diamond, mirages and light guiding in optical fibres.

Lenses: 1/v − 1/u = 1/f, m = v/u, and power P = 1/f (f in metres) in dioptres; a convex lens has positive power and a concave lens negative power.

Human eye: cornea plus lens focus light on the retina; rods respond in dim light, cones in bright light and colour; near point about 25 cm and far point infinity for a normal eye.

Defects: myopia (image in front of retina) is corrected by a concave lens, hypermetropia (image behind retina) by a convex lens, and presbyopia by bifocal lenses.

Dispersion: a prism splits white light into VIBGYOR because n is largest for violet and smallest for red; the blue sky comes from scattering of shorter wavelengths and red sunsets from the longer path through the atmosphere.

Ohm's law: V = IR at constant temperature; current I = Q/t in amperes and potential difference V = W/Q in volts.

Resistance of a wire: R = ρL/A, with ρ in ohm-metre; resistance rises with length and temperature and falls as cross-sectional area increases.

Series: same current through each element, R = R₁ + R₂ + …; parallel: same voltage across each branch, 1/R = 1/R₁ + 1/R₂ + …, so the total is less than the smallest branch resistance.

Electric power P = VI = I²R = V²/R in watts; commercial energy in kWh = (watt × hour)/1000, and 1 kWh = 3.6 × 10⁶ J.

Heating effect H = I²Rt is used in electric iron, heater, bulb filament and fuse; a fuse has a low melting point and is connected in the live wire to break overloads.

Magnetic field lines run from N to S outside a magnet, are closed loops and never cross; the right-hand thumb rule gives the field direction around a straight current-carrying conductor.

A current-carrying solenoid behaves like a bar magnet with N and S ends; field strength increases with current and with number of turns per unit length.

Force on a conductor: F = BIL sin θ, with direction from Fleming's left-hand rule - forefinger field, middle finger current, thumb thrust.

Electromagnetic induction: changing magnetic flux induces an emf (Faraday); Fleming's right-hand rule gives induced current direction; an AC generator uses slip rings while a DC generator uses a split-ring commutator.

Domestic supply in India is 220 V, 50 Hz, with live (red/brown), neutral (black/blue) and earth (green) wires; the earth wire provides a low-resistance path so a faulty metal body does not give a shock.

Waste management hierarchy - refuse, reduce, reuse, repurpose, recycle - ranks avoiding waste creation above treating or dumping it.

Forest conservation: Chipko movement (tree hugging), Joint Forest Management sharing produce with local communities, and protected areas - national parks, wildlife sanctuaries and biosphere reserves.

Water harvesting: khadins and tanks in Rajasthan, bamboo drip irrigation in Meghalaya, check dams and rooftop collection; large dams give water and electricity but displace people and submerge forests.

Coal, petroleum and natural gas are exhaustible fossil fuels formed over millions of years from buried organic matter; they are non-renewable on a human timescale.

Energy flow in food chains is unidirectional and about 10% passes between trophic levels, so chains rarely exceed four or five levels; non-biodegradable pesticides biomagnify at higher levels.

Air pollution: SO₂ and NOₓ cause acid rain of pH below 5.6; CO binds haemoglobin more strongly than oxygen; CFCs destroy stratospheric ozone over Antarctica and are controlled by the Montreal Protocol.

Greenhouse gases - CO₂, CH₄, N₂O, water vapour, CFCs - absorb infrared radiation and warm the earth; CO₂ from fossil fuel burning is the largest single contributor.

Eutrophication: excess nitrates and phosphates from fertilisers and sewage trigger algal blooms that die, decompose and deplete dissolved oxygen, killing fish.

Sustainable management combines the three Rs with equitable sharing of benefits; the 1992 Rio Earth Summit produced Agenda 21, and biodiversity hotspots include the Western Ghats and the Himalayas.