Bihar BSEB Matric Science cheat sheet

A balanced equation has the same number of atoms of each element on both sides, because mass is conserved; never change formulas while balancing, only coefficients.

Combination: A + B → AB (CaO + H2O → Ca(OH)2, strongly exothermic). Decomposition: AB → A + B (CaCO3 on heating gives CaO + CO2; electrolysis of water gives 2H2 + O2).

Displacement occurs when a more reactive metal replaces a less reactive one: Zn + CuSO4 → ZnSO4 + Cu; Fe + CuSO4 → FeSO4 + Cu.

Double displacement with precipitation: Pb(NO3)2 + 2KI → PbI2 (yellow precipitate) + 2KNO3; also AgNO3 + NaCl → AgCl (white) + NaNO3.

Oxidation is gain of oxygen or loss of hydrogen; reduction is the reverse. The substance oxidised acts as reducing agent and the one reduced as oxidising agent.

Photolytic decomposition in sunlight: 2AgCl → 2Ag + Cl2 (white turns grey); 2AgBr → 2Ag + Br2; used in black-and-white photography.

Rusting: 4Fe + 3O2 + xH2O → 2Fe2O3·xH2O, an oxidation plus combination; prevented by painting, oiling, greasing or galvanising with zinc.

Rancidity is oxidation of fats and oils giving bad smell and taste; checked by antioxidants, airtight containers, refrigeration or flushing with nitrogen.

pH scale runs 0 to 14: pH < 7 acidic, pH = 7 neutral, pH > 7 basic; a fall of one pH unit means ten times more H+ ions.

Indicators: blue litmus turns red in acid, red litmus turns blue in base; methyl orange is red in acid and yellow in base; phenolphthalein is colourless in acid and pink in base.

Acid + metal → salt + hydrogen; acid + metal carbonate or bicarbonate → salt + water + CO2 (the gas turns lime water milky).

Acid + base → salt + water (neutralisation, exothermic). Metal oxide + acid → salt + water; non-metal oxide + base → salt + water, e.g. CO2 + 2NaOH → Na2CO3 + H2O.

Strong acids (HCl, H2SO4, HNO3) ionise completely and conduct well; weak acids (acetic, carbonic) ionise partly; conductivity depends on H+ concentration.

Chlor-alkali process on brine: 2NaCl + 2H2O → 2NaOH + Cl2 (anode) + H2 (cathode).

Common salts: bleaching powder Ca(OCl)Cl, baking soda NaHCO3, washing soda Na2CO3·10H2O, plaster of Paris CaSO4·½H2O, common salt NaCl.

Washing soda removes temporary and permanent hardness by precipitating calcium and magnesium ions; hard water produces scum with soap.

Reactivity series (decreasing): K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au > Pt. Metals above hydrogen displace hydrogen from dilute acids.

Reaction with water: K, Na, Ca react with cold water; Mg with hot water; Fe, Zn only with steam; Cu, Ag, Au do not react.

Metal oxides are basic (Na2O, MgO); non-metal oxides are acidic (CO2, SO2); amphoteric oxides such as Al2O3 and ZnO react with both acid and base.

Ionic bonding: metal loses electrons to form a cation, non-metal gains to form an anion; NaCl and MgCl2 are ionic, conduct when molten or dissolved.

Metallurgy: roasting heats a sulphide ore in excess air (ZnS → ZnO); calcination heats a carbonate ore in limited air (CaCO3 → CaO).

Highly reactive metals (K, Na, Ca, Al) are extracted by electrolytic reduction; moderately reactive ones (Fe, Zn, Pb) by reduction with carbon.

Alloys: brass = Cu + Zn, bronze = Cu + Sn, solder = Pb + Sn, steel = Fe + C; alloying changes hardness and lowers melting point.

Aqua regia (3 parts HCl : 1 part HNO3) dissolves gold; gold has density 19.3 g/cm3 and is the most malleable metal.

Storage: sodium and potassium in kerosene, white phosphorus in water, to keep them away from air and moisture.

Carbon is tetravalent and shows catenation, forming stable single, double and triple bonds; this gives millions of carbon compounds.

Alkanes CnH2n+2 are saturated (single bonds); alkenes CnH2n have one double bond; alkynes CnH2n-2 have a triple bond; all burn with a sooty flame except alkanes.

Members of a homologous series differ by one CH2 unit and 14 u in molar mass, with similar chemical properties and a gradual change in physical properties.

Ethanol with sodium gives sodium ethoxide and hydrogen; with concentrated H2SO4 at 443 K it dehydrates to ethene.

Ethanoic acid (CH3COOH) + NaHCO3 → CH3COONa + H2O + CO2; it turns blue litmus red and neutralises NaOH to sodium acetate.

Esterification: carboxylic acid + alcohol with a little concentrated H2SO4 gives an ester with a sweet fruity smell (used in perfumes and flavours).

Soap is a sodium salt of a long-chain fatty acid; in water it forms micelles that trap oily dirt. In hard water it forms scum and loses cleaning power.

Detergents are ammonium or sulphonate salts and work even in hard water; soaps are more biodegradable than detergents.

Incomplete combustion of carbon compounds gives soot and carbon monoxide; saturated hydrocarbons burn with a clean blue flame.

Mendeleev arranged elements by atomic mass and stated that properties are periodic functions of atomic mass; he left gaps for undiscovered elements such as eka-aluminium.

Modern periodic law: properties of elements are periodic functions of their atomic number Z; the table has 7 horizontal periods and 18 vertical groups.

Across a period (left to right): atomic radius decreases, metallic character decreases, non-metallic character and electronegativity increase, valency first rises then falls.

Down a group (top to bottom): atomic radius increases, metallic character increases, ionisation energy decreases, valency remains the same.

Group 1 alkali metals are highly reactive with water; Group 2 alkaline earth metals; Group 17 halogens are highly reactive non-metals; Group 18 noble gases have a complete octet and are almost inert.

Hydrogen is placed separately because it resembles alkali metals in forming H+ and halogens in forming H-.

Early attempts: Döbereiner's triads (1817) and Newlands' law of octaves (1866) failed because they did not fit all known elements.

Atomic number = number of protons = number of electrons in a neutral atom; valence electrons decide chemical properties.

Laws of reflection: angle of incidence = angle of reflection, and the incident ray, reflected ray and normal lie in the same plane.

For a spherical mirror f = R/2; mirror formula 1/v + 1/u = 1/f; magnification m = h'/h = -v/u. A negative m means a real inverted image.

Concave mirror: real, inverted image for object beyond F; virtual, erect and magnified for object within F (shaving mirror); parallel rays meet at F.

Convex mirror: always virtual, erect and diminished, with a wider field of view, so it is used as a rear-view mirror and in blind corners.

Snell's law: n = sin i / sin r. A ray going from rarer to denser medium bends towards the normal and the reverse bends away.

Refractive index n = c/v; absolute value is 1 for vacuum, 1.33 for water and about 1.5 for glass; higher n means slower light in the medium.

Lens formula 1/v - 1/u = 1/f; power P = 1/f with f in metres, unit dioptre (D); a convex lens is converging with positive power.

Total internal reflection occurs when light travels from denser to rarer medium and the angle of incidence exceeds the critical angle; it causes the sparkle of diamonds and optical fibre transmission.

The cornea and the crystalline lens focus light onto the retina; the ciliary muscles change the lens curvature, a process called accommodation.

Normal eye: near point 25 cm and far point infinity; the least distance of distinct vision is 25 cm.

Myopia (short-sightedness) is corrected by a concave lens; hypermetropia (long-sightedness) by a convex lens; presbyopia by bifocal lenses.

Rods respond to dim light and cones to bright light and colour; the blind spot is where the optic nerve leaves the eye.

Dispersion by a prism splits white light into VIBGYOR; violet is deviated most and red least because of the shortest and longest wavelengths.

A rainbow forms by refraction, dispersion and total internal reflection inside water droplets, with the sun behind the observer.

Atmospheric refraction causes twinkling of stars, the apparent flattening of the sun at sunrise and sunset, and the advance of sunrise.

Scattering explains the blue sky (short wavelengths scatter more) and the red sun at sunrise and sunset; the Tyndall effect shows scattering by colloidal particles.

Ohm's law: V = IR at constant temperature; R = ρl/A, where ρ is resistivity in ohm-metre, l length and A area of cross-section.

Charge Q = It; one coulomb is the charge carried by 1 A in 1 s; conventional current flows opposite to electron flow.

Series circuit: R = R1 + R2 + R3; the current is the same in every part and the voltage divides in proportion to resistance.

Parallel circuit: 1/R = 1/R1 + 1/R2 + 1/R3; the voltage is the same across each branch and the current divides.

Power P = VI = I²R = V²/R, unit watt; electrical energy = P × t, and 1 kWh = 3.6 × 10^6 J.

Heating effect H = I²Rt; this is the principle of the electric iron, heater and fuse. Nichrome has high resistivity and high melting point.

An ammeter is connected in series and has very low resistance; a voltmeter is connected in parallel and has very high resistance.

Copper has low resistivity, so it is used for connecting wires; the resistance of a wire rises with length and falls with greater area of cross-section.

Oersted showed that a current-carrying conductor produces a magnetic field around it; the field lines form concentric circles.

Right-hand thumb rule: with the thumb pointing along the current, the curled fingers give the direction of the magnetic field.

Inside a current-carrying solenoid the field is uniform and the solenoid behaves like a bar magnet; a soft iron core makes an electromagnet.

Fleming's left-hand rule gives the direction of force on a current-carrying conductor in a magnetic field: thumb = force, forefinger = field, middle finger = current. This is the principle of the electric motor.

Fleming's right-hand rule gives the direction of induced current, the principle of the generator.

Electromagnetic induction: a changing magnetic field linked with a coil induces a current in it (Faraday); a moving magnet into and out of a coil reverses the current.

AC reverses direction periodically and in India has a frequency of 50 Hz and 220 V; DC flows in one direction only, as from a cell.

Domestic wiring: live wire red or brown, neutral black or blue, earth green; the fuse is placed in the live wire and the earth wire gives safety.

An electric bell uses an electromagnet with a soft iron core and an interrupter that repeatedly makes and breaks the circuit.

Renewable sources: solar, wind, hydro, biomass, geothermal, tidal and wave. Non-renewable: coal, petroleum and natural gas, which are finite and add CO2.

A solar cell made of silicon converts light directly into electricity; a solar panel is many cells joined together, and a solar cooker uses a black surface with a glass cover.

Biogas is about 75% methane, produced by anaerobic decomposition of cow dung and plant waste; the slurry left is used as manure.

Wind energy needs a minimum speed of about 15 km/h; the blades of a windmill turn a turbine coupled to a generator.

Hydro power converts the potential energy of water stored at a height into electricity through a turbine and generator.

Tidal energy comes from the gravitational pull of the moon; ocean thermal energy conversion uses the temperature difference between surface and deep water.

Burning fossil fuels releases SO2 and NOx, which cause acid rain, and CO2, which is a greenhouse gas.

Nuclear fission of uranium-235 releases large energy; safe disposal of spent fuel is the main hazard.

An ideal fuel has a high calorific value, low cost, low pollution, easy storage and transport, and a moderate ignition temperature.

Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 in chloroplasts using chlorophyll and sunlight; stomata allow CO2 entry and O2 exit.

Nutrition types: autotrophic, and heterotrophic (holozoic, saprophytic such as Rhizopus, parasitic).

Human digestion: salivary amylase digests starch; pepsin acts on protein in the acidic stomach; trypsin and lipase act in the small intestine; villi absorb nutrients.

Aerobic respiration of one glucose molecule yields far more ATP (about 38) than anaerobic (2); anaerobic respiration in muscles gives lactic acid and cramps.

Alveoli provide a large surface for gas exchange; haemoglobin in red blood cells carries oxygen.

The human heart has four chambers and double circulation; arteries carry blood away from the heart, veins towards it.

The nephron is the functional unit of the kidney; urine formation involves filtration, reabsorption and secretion; dialysis replaces kidney function.

Xylem transports water and minerals upward only; phloem transports food, mainly sucrose, in both directions.

Transpiration pulls water up the plant and cools the leaf; it is regulated by guard cells.

A neuron has dendrites, a cell body and an axon; the impulse is electrical along the neuron and chemical across a synapse.

A reflex action is a quick, involuntary response through a reflex arc: receptor → sensory nerve → spinal cord → motor nerve → muscle.

CNS = brain + spinal cord; PNS = cranial and spinal nerves. The cerebrum controls thinking, the cerebellum balance, the medulla involuntary actions such as breathing.

Pituitary secretes growth hormone; thyroid secretes thyroxine and needs iodine (deficiency causes goitre); pancreas secretes insulin; adrenal secretes adrenaline.

Insulin lowers blood glucose, and glucagon raises it, an example of feedback control of hormone levels.

Plant hormones: auxin promotes cell elongation and phototropism; gibberellin promotes stem elongation; cytokinin promotes cell division; abscisic acid inhibits growth and closes stomata.

Tropisms are directional responses to a stimulus (phototropism, geotropism); nastic movements such as the touch-me-not leaf are non-directional.

Hormones act slowly and for a longer time, while nerve impulses are fast and short-lived.

Asexual modes: binary fission (Amoeba, Leishmania), budding (Hydra, yeast), fragmentation (Spirogyra), regeneration (Planaria), spore formation (Rhizopus), vegetative propagation (sugarcane, rose).

DNA copying during reproduction produces variation; errors in copying create new variations that may help survival.

A flower has sepals, petals, androecium (stamens with anther and filament) and gynoecium (carpel with stigma, style and ovary).

Pollination is transfer of pollen to the stigma; self-pollination occurs within one flower, cross-pollination between flowers; agents are wind, water and insects.

Human male: testes produce sperm and testosterone; female: ovaries produce ova and oestrogen; fertilisation normally occurs in the fallopian tube.

The placenta allows exchange of glucose, oxygen and waste between mother and embryo; gestation is about nine months in humans.

Contraception methods: barrier (condom), hormonal (pills), intrauterine devices, and surgical (vasectomy, tubectomy).

Puberty changes are triggered by hormones; in plants, vegetative propagation produces clones that are genetically identical.

Mendel's laws: dominance, segregation of alleles, and independent assortment of two traits.

Monohybrid F2 phenotypic ratio is 3:1 and genotypic ratio 1:2:1; dihybrid F2 ratio is 9:3:3:1.

Genotype is the gene combination (TT, Tt, tt) and phenotype is the visible trait; TT and Tt are tall, tt is short.

In humans, females are XX and males XY; the father's sperm determines the sex of the child.

Inherited traits are carried by genes in germ cells; acquired traits during a lifetime are not passed on to the next generation.

Homologous organs have the same basic structure with different functions (human forelimb, bird wing); analogous organs have different structures with similar functions (bird wing, butterfly wing).

Fossils give direct evidence of past life; Darwin's natural selection explains survival of favourable variations.

Speciation occurs when populations become reproductively isolated; genetic drift and gene flow change gene frequencies.

An ecosystem has biotic components (producers, consumers, decomposers) and abiotic components such as light, temperature, water and soil.

A food chain runs producer → herbivore → carnivore; a network of chains forms a food web.

Ten per cent law: only about 10% of the energy at one trophic level passes to the next; the rest is lost mainly as heat.

Energy flow in an ecosystem is unidirectional, whereas nutrients such as carbon and nitrogen are cycled.

Biomagnification is the increase in concentration of a toxic substance such as a pesticide along successive trophic levels.

Biodegradable waste is broken down by microorganisms; non-biodegradable waste such as plastic persists and harms animals.

The ozone layer absorbs harmful ultraviolet radiation; chlorofluorocarbons deplete it and are controlled under the Montreal Protocol.

Waste management follows reduce, reuse and recycle, with segregation of biodegradable and non-biodegradable waste at source.

The three Rs are reduce, reuse and recycle; refusing unnecessary items and repairing rather than discarding also conserve resources.

Forests conserve soil and water, support biodiversity and act as watersheds; afforestation and controlled grazing protect them.

Joint Forest Management involves local communities with the forest department in protecting and using forest produce.

Protected areas: national parks, wildlife sanctuaries and biosphere reserves; Project Tiger is a conservation programme for tigers.

Water conservation practices: rainwater harvesting, watershed management, check dams, drip and sprinkler irrigation, and reuse of grey water.

Fossil fuels are finite and non-renewable, so conservation and a shift to solar, wind and biogas are necessary.

Stakeholders in forest management include local communities, the forest department, industry and environmental organisations.

Movements such as the Chipko movement showed that community participation can protect trees and local livelihoods.

River pollution control, such as the Ganga Action Plan, requires treatment of sewage and industrial effluent before discharge.