RBSE Secondary Science cheat sheet

Balanced chemical equation conserves atoms of each element on both sides; coefficients give mole ratios.

pH scale: pH < 7 acidic, pH = 7 neutral, pH > 7 basic; each unit is a tenfold change in H+ concentration.

Acid + base → salt + water (neutralisation); acid + metal → salt + hydrogen gas; acid + metal carbonate → salt + water + carbon dioxide.

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

Displacement reaction: a more reactive metal displaces a less reactive metal from its salt solution (e.g., Fe + CuSO4 → FeSO4 + Cu).

Homologous series: same general formula and functional group, successive members differ by –CH2– (14 u).

Periodic table: groups = valence electrons (main groups), periods = number of shells; metallic character increases down a group and decreases across a period.

Molar mass = sum of atomic masses; number of moles n = given mass / molar mass; 1 mol contains 6.022×10^23 particles.

Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 (in presence of chlorophyll and sunlight); occurs in chloroplasts.

Aerobic respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (38 ATP); anaerobic in muscle → lactic acid + energy (2 ATP).

Human digestive enzymes: salivary amylase digests starch; pepsin (stomach) digests protein; trypsin (pancreas) digests protein; lipase digests fats.

Nephron is the functional unit of kidney: filtration in glomerulus, selective reabsorption in tubule, urine formation.

Reflex arc pathway: receptor → sensory neuron → spinal cord (relay) → motor neuron → effector (muscle/gland).

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

Mendel's laws: dominance (F1 all tall from TT × tt), segregation (alleles separate during gamete formation), independent assortment (two traits).

Evolution evidence: homologous organs (same structure, different function), analogous organs (different structure, same function), fossils.

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

Mirror formula: 1/f = 1/v + 1/u; magnification m = -v/u = h_i/h_o; sign convention: distances measured from pole, positive in direction of incident light.

Refraction: Snell's law n1 sin i = n2 sin r; light bends toward normal when entering denser medium (air→glass).

Lens formula: 1/f = 1/v – 1/u; power P = 1/f (in metres), unit dioptre (D).

Human eye: myopia corrected by concave lens; hypermetropia by convex lens; presbyopia due to loss of accommodation.

Ohm's law: V = IR at constant temperature; resistance R = ρL/A; series R = R1+R2+…; parallel 1/R = 1/R1+1/R2+…

Electric power P = VI = I^2R = V^2/R; energy consumed in kWh = power(kW) × time(h).

Magnetic effect: current-carrying straight conductor produces concentric circular field lines (right-hand thumb rule); solenoid behaves like bar magnet; force on conductor F = BIL sinθ (Fleming's left-hand rule).

Conventional current direction is opposite to electron flow; household wiring: live (red/brown), neutral (black/blue), earth (green).

Electrical fuse works on heating effect of current (I^2R); rated current must be slightly above normal operating current.

Sources of energy: renewable (solar, wind, hydro, biomass, geothermal) vs non-renewable (coal, petroleum, natural gas, nuclear).

Solar cell converts light directly to electricity (photovoltaic effect); solar cooker uses black surface to absorb heat.

Food chain: producer → primary consumer → secondary consumer → tertiary consumer; 10% law of energy transfer between trophic levels.

Ozone layer (stratosphere) absorbs UV radiation; depletion caused by CFCs and halons.

Sustainable management: 3R strategy (Reduce, Reuse, Recycle); rainwater harvesting; check dams; afforestation.

Greenhouse gases: CO2, CH4, N2O, water vapour; enhanced greenhouse effect leads to global warming.

Observation vs inference: observation is what you see/measure; inference is an explanation based on observation.

Controlled experiment: independent variable is changed, dependent variable is measured, all other variables kept constant.

Litmus test: acids turn blue litmus red; bases turn red litmus blue; neutral substances show no change.

To test for CO2 gas: pass through limewater (calcium hydroxide solution); it turns milky (CaCO3 precipitate).

Flame test: sodium → golden yellow; potassium → lilac; calcium → brick red; copper → blue-green.

Reading a measuring cylinder: eye level at bottom of meniscus; record to nearest marked division with one estimated digit.

Graphing: plot independent variable on x-axis, dependent on y-axis; draw line of best fit; slope = rate of change.

Precision vs accuracy: precision = closeness of repeated measurements; accuracy = closeness to true value.