Haryana BSEH Secondary Science cheat sheet

Acids turn blue litmus red and release H+ (H3O+) in water; bases turn red litmus blue and release OH- in water; salts form when acid and base neutralise: HCl + NaOH -> NaCl + H2O.

pH scale runs 0-14: pH < 7 acidic, pH = 7 neutral, pH > 7 basic; each unit is a tenfold change in H+ concentration, so pH 3 is 100 times more acidic than pH 5.

Metal + dilute acid -> salt + hydrogen gas (Zn + 2HCl -> ZnCl2 + H2); the gas burns with a pop test. Metals below hydrogen in the reactivity series (Cu, Ag, Au) do not react with dilute acids.

Reactivity series (decreasing): K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Hg > Ag > Au. A more reactive metal displaces a less reactive one from its salt solution (Fe + CuSO4 -> FeSO4 + Cu).

Thermal decomposition of metal carbonates gives metal oxide + CO2 (CaCO3 on heating -> CaO + CO2); bicarbonates give carbonate + water + CO2 (2NaHCO3 -> Na2CO3 + H2O + CO2).

Combination, decomposition, displacement and double displacement are the four basic reaction types; double displacement in solution often yields a precipitate (AgNO3 + NaCl -> AgCl precipitate + NaNO3).

Oxidation is loss of electrons or gain of oxygen; reduction is gain of electrons or loss of hydrogen. In a redox reaction the oxidising agent is itself reduced and the reducing agent is itself oxidised.

In the modern periodic table, elements are arranged by increasing atomic number; groups are vertical columns with the same number of valence electrons, periods are horizontal rows with the same number of shells.

Covalent bonds form by sharing electrons between non-metals (H2, O2, H2O, CH4); ionic bonds form by transfer of electrons from metal to non-metal (NaCl, MgCl2); ionic compounds conduct electricity when molten or dissolved, not when solid.

Cell organelles and roles: nucleus controls activity and holds DNA; mitochondria release energy by respiration; ribosomes make protein; chloroplasts carry out photosynthesis; vacuole stores sap and maintains turgor.

Plant cells have a rigid cellulose cell wall and chloroplasts; animal cells lack a cell wall and chloroplasts but have centrioles. Both have a plasma membrane, cytoplasm and nucleus.

Photosynthesis: 6CO2 + 6H2O in the presence of chlorophyll and sunlight -> C6H12O6 + 6O2; it occurs in chloroplasts and converts light energy into chemical energy stored in glucose.

Aerobic respiration: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy; anaerobic respiration in muscle gives lactic acid, and in yeast gives ethanol + CO2 (fermentation).

Xylem transports water and dissolved minerals upward from roots and is dead, lignified tissue; phloem transports synthesised food in both directions and is living tissue.

Human digestive order: mouth (salivary amylase digests starch) -> oesophagus -> stomach (HCl and pepsin digest protein) -> small intestine (main absorption, villi increase surface area) -> large intestine (water absorption).

Blood components: plasma (transports dissolved substances), red blood cells (haemoglobin carries oxygen, no nucleus in mammals), white blood cells (defence), platelets (clotting).

Mendel's laws: traits are controlled by pairs of factors (genes); dominant alleles mask recessive ones; during gamete formation the two alleles separate (law of segregation) and assort independently.

Reproduction: asexual (binary fission, budding, fragmentation, vegetative propagation) produces genetically identical offspring from one parent; sexual reproduction involves gametes and produces variation.

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

For a plane mirror the image is virtual, erect, laterally inverted, and as far behind the mirror as the object is in front; image size equals object size.

Spherical mirrors: concave mirrors converge light and can form real or virtual images; convex mirrors diverge light and always form virtual, erect, diminished images (used as rear-view mirrors).

Mirror formula 1/v + 1/u = 1/f and magnification m = -v/u = h'/h; for lenses 1/v - 1/u = 1/f and m = v/u. Sign convention: distances measured from the pole/optical centre, against incident light negative.

Refraction occurs because light changes speed between media; Snell's law n1 sin i = n2 sin r, and refractive index n = speed of light in vacuum / speed in medium.

A convex lens converges parallel rays to its focal point; a concave lens diverges them. Power of a lens P = 1/f (in metres), unit dioptre (D).

Sound is a longitudinal mechanical wave needing a medium; it travels fastest in solids, slower in liquids, slowest in gases, and cannot travel through vacuum.

Audible range for humans is about 20 Hz to 20,000 Hz; frequency determines pitch and amplitude determines loudness; sound speed in air is roughly 340 m/s at room temperature.

Electric current produces a magnetic field (Oersted's discovery); a current-carrying solenoid behaves like a bar magnet, and a changing magnetic field can induce a current (electromagnetic induction).

Ohm's law: V = IR at constant temperature; resistance R = rho L / A, so resistance increases with length and decreases with cross-sectional area.

Series circuit: same current through all components, total resistance R = R1 + R2 + R3, voltage divides in proportion to resistance.

Parallel circuit: same voltage across all branches, 1/R = 1/R1 + 1/R2 + ..., total resistance is less than the smallest branch, current divides inversely with resistance.

Electric power P = VI = I^2 R = V^2 / R; energy consumed = P x t, and one commercial unit (kWh) = 3.6 x 10^6 joules.

Heating effect of current: H = I^2 R t (Joule's law); this effect is used in electric irons, heaters, fuses and filament bulbs.

A fuse is a low-melting-point wire in series with the live wire; it melts and breaks the circuit on overload or short circuit. Earthing connects the metal body of an appliance to the earth to prevent shock.

Magnetic effect: field lines run from north to south outside a magnet; the field of a straight wire forms concentric circles, and the right-hand thumb rule gives the field direction.

Force on a current-carrying conductor in a magnetic field is given by Fleming's left-hand rule (forefinger = field, middle = current, thumb = motion); this is the basis of the electric motor.

Fleming's right-hand rule applies to generators: thumb = induced current, forefinger = field, middle = motion of conductor.

The atmosphere is about 78% nitrogen, 21% oxygen, 0.9% argon and 0.04% carbon dioxide by volume; the ozone layer in the stratosphere absorbs harmful ultraviolet radiation.

The greenhouse effect is natural warming by gases such as CO2, methane, water vapour and CFCs; an enhanced effect from human emissions is linked to global warming and climate change.

Biogeochemical cycles recycle elements: the carbon cycle (photosynthesis, respiration, combustion, decomposition), the nitrogen cycle (fixation by Rhizobium and cyanobacteria, nitrification, denitrification) and the water cycle.

Soil erosion is accelerated by deforestation, overgrazing and steep slopes; contour ploughing, terracing, strip cropping and shelter belts reduce it.

Three R's of waste management: reduce, reuse, recycle; biodegradable waste (kitchen waste, paper) is decomposed by microbes, non-biodegradable waste (plastics, glass) persists for long periods.

Depletion of the ozone layer is caused mainly by chlorofluorocarbons (CFCs); the Montreal Protocol is the international agreement to phase them out.

Acid rain forms when sulphur dioxide and nitrogen oxides dissolve in rain to give sulphuric and nitric acids; it damages buildings, soils, crops and aquatic life.

Water conservation methods include rainwater harvesting, drip and sprinkler irrigation, watershed management and treatment of sewage before discharge.

Biodiversity is the variety of species and ecosystems; hotspots and protected areas (national parks, sanctuaries, biosphere reserves) conserve species, and extinction reduces ecosystem stability.

Read a measuring cylinder or burette at eye level, taking the bottom of the meniscus as the reading; a tilted eye causes parallax error.

Before heating a test tube, point its mouth away from yourself and others and heat gently along the side; use a test-tube holder, never bare hands.

Litmus test: dip blue litmus in the solution; reddening indicates acid. Confirm with red litmus turning blue for a base; neutral solutions change neither.

To test for hydrogen gas, bring a burning splint near the mouth of the tube; a pop sound confirms hydrogen. Carbon dioxide turns limewater milky; oxygen relights a glowing splint.

In a circuit, connect the ammeter in series and the voltmeter in parallel with the component; check polarity (+ to +) and start with the highest range.

Focal length of a concave mirror by distant-object method: focus a distant object on a screen; the sharpest image distance from the mirror equals the focal length.

Verify Ohm's law by recording V and I for several values, plotting V against I; a straight-line graph through the origin gives resistance as the slope.

When using a microscope or lens, first focus with the coarse adjustment at low power, then sharpen with the fine adjustment; keep both eyes open.

Record observations in a table with units and repeat readings to reduce random error; report the mean and identify the constant variable in controlled experiments.

A hypothesis is a testable prediction; an experiment changes one independent variable, measures the dependent variable and holds all other factors constant.

Accuracy is closeness to the true value; precision is closeness of repeated readings to one another. Random errors scatter both ways; systematic errors shift all readings in one direction.

SI base units: metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), candela (luminous intensity).

Scientific notation expresses numbers as a x 10^n with 1 <= a < 10; convert units carefully, e.g. 1 km = 10^3 m, 1 g = 10^-3 kg, 1 kWh = 3.6 x 10^6 J.

A control group receives no treatment or a placebo; comparing it with the experimental group isolates the effect of the variable being tested.

Correlation does not prove causation; a valid conclusion requires controlled evidence and reproducibility by independent workers.

Applications of science: semiconductors in electronics, electromagnets in motors and cranes, antibiotics against bacteria (not viruses), vaccines for immunity, and solar cells for renewable energy.

A scientific claim should be judged on evidence, peer review and reproducibility, not on popularity or the authority of the speaker.

Balanced diet nutrients: carbohydrates and fats give energy, proteins build and repair tissue, vitamins and minerals regulate body processes, water and roughage aid digestion.

Deficiency diseases: vitamin A - night blindness; vitamin B1 - beriberi; vitamin C - scurvy; vitamin D - rickets; iron - anaemia; iodine - goitre; calcium - weak bones.

Protein-energy malnutrition: marasmus from deficiency of protein and total energy (severe wasting), kwashiorkor from protein deficiency with adequate energy (oedema, swollen belly).

Communicable diseases spread by air (TB, common cold), water and food (cholera, typhoid), vectors (malaria by female Anopheles mosquito, dengue by Aedes) and contact (ringworm).

Non-communicable diseases include diabetes, hypertension, obesity and cancer; they are influenced by diet, inactivity, tobacco and alcohol rather than by pathogens.

Immunity: vaccination introduces weakened or killed antigens so the body produces antibodies and memory cells, giving protection against later infection.

Personal hygiene: wash hands with soap before eating and after using the toilet, boil or filter drinking water, cover food, bathe regularly and keep nails trimmed.

Malaria prevention: drain stagnant water, use mosquito nets and repellents; diarrhoea prevention: oral rehydration solution (ORS) replaces water and electrolytes.

First aid basics: for burns cool with running water, for bleeding apply pressure, for fractures immobilise the limb, and never give food to an unconscious person; seek medical help promptly.