RBSE VU General Science cheat sheet

Three states: solid (fixed shape and volume, particles closely packed, vibrate only), liquid (fixed volume, takes container shape, particles slide past each other), gas (no fixed shape or volume, particles far apart, move rapidly).

Changes of state: melting (solid→liquid), freezing (liquid→solid), evaporation/boiling (liquid→gas), condensation (gas→liquid), sublimation (solid→gas directly), deposition (gas→solid directly).

Pure substances: elements (one kind of atom, cannot be split chemically) and compounds (two or more elements chemically combined in fixed ratio, e.g., H₂O, CO₂).

Mixtures: homogeneous (uniform composition, e.g., salt solution, air) vs heterogeneous (non-uniform, e.g., sand and iron filings). Components retain their properties and can be separated physically.

Separation techniques: filtration (insoluble solid from liquid), evaporation/crystallisation (soluble solid from solution), distillation (liquid from solution or two miscible liquids with different boiling points), fractional distillation (petroleum, liquid air), chromatography (separating coloured pigments or dissolved substances), magnetic separation (iron from mixtures), sieving, decantation, centrifugation.

Physical change: no new substance formed, usually reversible (melting, dissolving). Chemical change: new substance formed, usually irreversible (burning, rusting, cooking).

Density = mass/volume; objects less dense than a fluid float, more dense sink. Ice floats on water because its density is lower.

Diffusion: spreading of particles from high to low concentration; faster at higher temperature and in gases because particles move faster and are farther apart.

Brownian motion: random movement of small particles suspended in a fluid caused by collisions with fast-moving fluid molecules; evidence for the particulate nature of matter.

Atom: nucleus (protons + neutrons) surrounded by electrons in shells. Proton mass ≈ 1 u, charge +1; neutron mass ≈ 1 u, charge 0; electron mass ≈ 1/1836 u, charge −1.

Atomic number Z = number of protons (defines the element). Mass number A = protons + neutrons. Number of neutrons = A − Z.

Isotopes: atoms of the same element with different numbers of neutrons (same Z, different A), e.g., ¹²C and ¹⁴C; same chemical properties, different masses.

Electron shells fill in order 2, 8, 8, 18…; the outermost shell (valence shell) determines chemical behaviour. Atoms with full outer shells (noble gases) are unreactive.

Ion: atom that has gained or lost electrons. Metals lose electrons → positive ions (cations); non-metals gain electrons → negative ions (anions).

Ionic bond: electrostatic attraction between oppositely charged ions, usually metal + non-metal (e.g., NaCl: Na⁺ and Cl⁻). High melting points, conduct electricity when molten or dissolved.

Covalent bond: sharing of electron pairs between non-metal atoms (e.g., H₂, O₂, H₂O, CH₄). Usually low melting points; do not conduct electricity (except graphite).

Metallic bond: positive metal ions in a ‘sea’ of delocalised electrons; explains conductivity, malleability and ductility of metals.

Valency: combining power of an element; group 1 = 1, group 2 = 2, group 13 = 3, group 15 = 3, group 16 = 2, group 17 = 1. Chemical formula is written by balancing valencies (e.g., Al₂O₃).

Law of conservation of mass: mass of reactants = mass of products in a closed system; equations must be balanced (same number of each type of atom on both sides).

Combination reaction: two or more reactants → one product (e.g., 2H₂ + O₂ → 2H₂O). Decomposition reaction: one reactant → two or more products, often by heat, light or electricity (e.g., CaCO₃ → CaO + CO₂).

Displacement reaction: a more reactive element displaces a less reactive one from its compound (e.g., Zn + CuSO₄ → ZnSO₄ + Cu). Reactivity series: K, Na, Ca, Mg, Al, Zn, Fe, Pb, (H), Cu, Ag, Au.

Double displacement (precipitation) reaction: ions exchange partners, often forming an insoluble precipitate (e.g., AgNO₃ + NaCl → AgCl↓ + NaNO₃).

Exothermic reaction releases heat (combustion, neutralisation, respiration); endothermic reaction absorbs heat (thermal decomposition of CaCO₃, photosynthesis).

Oxidation = loss of electrons / gain of oxygen / loss of hydrogen; reduction = gain of electrons / loss of oxygen / gain of hydrogen. Redox reactions occur together.

Rate of reaction increases with higher temperature, higher concentration, larger surface area of solid reactants, and presence of a catalyst. Catalyst speeds up a reaction without being used up.

Reversible reactions reach dynamic equilibrium when forward and reverse rates are equal; changing temperature, pressure or concentration shifts the equilibrium (Le Chatelier’s principle).

Acid: proton (H⁺) donor; produces H⁺ ions in water. Base: proton acceptor; soluble bases are alkalis, producing OH⁻ ions in water.

pH scale 0–14: pH < 7 acidic, pH = 7 neutral, pH > 7 alkaline. Each unit represents a tenfold change in H⁺ concentration.

Indicators: litmus (red in acid, blue in alkali), methyl orange (red in acid, yellow in alkali), phenolphthalein (colourless in acid, pink in alkali), universal indicator (full colour range).

Neutralisation: acid + base → salt + water (e.g., HCl + NaOH → NaCl + H₂O). Acid + metal → salt + hydrogen gas. Acid + metal carbonate → salt + water + carbon dioxide.

Common acids: hydrochloric (HCl), sulfuric (H₂SO₄), nitric (HNO₃), ethanoic (CH₃COOH, weak). Common bases: sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂), ammonia (NH₃).

Salt formation: by neutralisation, by acid + metal, by acid + carbonate, or by precipitation. Soluble salts prepared by crystallisation; insoluble salts by precipitation and filtration.

Uses: sulfuric acid in batteries and fertilisers; hydrochloric acid in stomach digestion and cleaning metals; sodium hydroxide in soap making; calcium carbonate (limestone) in building and as antacid.

Strong acid fully ionises in water (HCl); weak acid partially ionises (CH₃COOH). Same distinction applies to strong and weak bases.

Metals: shiny, malleable, ductile, good conductors of heat and electricity, high melting points (except mercury, liquid at room temperature), sonorous. Non-metals: dull, brittle, poor conductors (except graphite), low melting points.

Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au. Metals above hydrogen displace H₂ from dilute acids; metals above carbon are extracted by electrolysis, those below by reduction with carbon.

Rusting of iron requires both oxygen and water; prevented by painting, oiling, galvanising (zinc coating), alloying (stainless steel) or sacrificial protection.

Alloys: mixtures of metals (or metal + non-metal) that are harder than pure metals, e.g., steel (Fe + C), brass (Cu + Zn), bronze (Cu + Sn), solder (Pb + Sn).

Carbon allotropes: diamond (tetrahedral, very hard, non-conductor), graphite (layers, soft, conducts), fullerene (C₆₀, cage-like). Same element, different structures → different properties.

Hydrocarbons: compounds of carbon and hydrogen only. Alkanes (single bonds, CₙH₂ₙ₊₂, e.g., methane CH₄), alkenes (one double bond, CₙH₂ₙ, e.g., ethene C₂H₄), alkynes (triple bond, CₙH₂ₙ₋₂, e.g., ethyne C₂H₂).

Functional groups: alcohols –OH (ethanol C₂H₅OH), carboxylic acids –COOH (ethanoic acid CH₃COOH), esters –COO– (fruity smells).

Combustion: hydrocarbon + oxygen → carbon dioxide + water (+ energy). Incomplete combustion produces carbon monoxide, a toxic gas.

Fossil fuels (coal, petroleum, natural gas) are finite; burning them releases CO₂, a greenhouse gas linked to global warming.

Cell theory: all living things are made of cells; the cell is the basic unit of life; new cells arise from existing cells by division.

Prokaryotic cell: no membrane-bound nucleus or organelles (bacteria). Eukaryotic cell: nucleus and membrane-bound organelles (plant, animal, fungal, protist cells).

Plant cell unique structures: cell wall (cellulose), chloroplasts (photosynthesis), large permanent vacuole. Animal cell: no cell wall or chloroplasts; small temporary vacuoles; centrioles.

Organelles: nucleus (controls activities, contains DNA), mitochondrion (respiration, ATP), ribosome (protein synthesis), endoplasmic reticulum (transport), Golgi apparatus (packaging), lysosome (digestion), chloroplast (photosynthesis).

Tissues: epithelial (covering), connective (bone, blood), muscle (movement), nervous (impulses), and in plants: epidermal, palisade mesophyll, xylem (water transport), phloem (food transport).

Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, using light energy trapped by chlorophyll; occurs in chloroplasts; rate limited by light intensity, CO₂ concentration and temperature.

Respiration: aerobic - C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP); anaerobic in muscles - glucose → lactic acid + energy; in yeast - glucose → ethanol + CO₂ + energy.

Transport: in humans, heart pumps blood through arteries (away from heart), veins (towards heart, valves) and capillaries (exchange). In plants, xylem carries water and minerals upward; phloem carries sugars both ways.

Excretion and homeostasis: kidneys remove urea and excess water/salts; skin and lungs also excrete. Homeostasis keeps internal conditions (temperature, blood glucose, water) stable.

DNA is a double helix of nucleotides (A, T, C, G); A pairs with T, C pairs with G. A gene is a section of DNA coding for a protein; chromosomes are packaged DNA.

Humans have 46 chromosomes (23 pairs); gametes have 23 (haploid). Mitosis produces two identical diploid cells for growth and repair; meiosis produces four genetically different haploid gametes.

Genotype = genetic makeup (e.g., Tt); phenotype = observable trait. Alleles: dominant (expressed when present), recessive (expressed only when homozygous). Homozygous = two identical alleles; heterozygous = two different alleles.

Monohybrid cross: Tt × Tt gives 3:1 dominant:recessive phenotype ratio and 1:2:1 genotype ratio. Punnett squares predict offspring probabilities.

Sex determination: human female XX, male XY; the father’s sperm determines the sex of the child (50% chance each).

Variation: continuous (height, mass, influenced by many genes and environment) vs discontinuous (blood group, tongue rolling). Sources: mutation, sexual reproduction (crossing over, independent assortment), environment.

Natural selection (Darwin): individuals with advantageous inherited variations survive and reproduce more, passing on those alleles; over many generations populations adapt. Evidence: fossils, homologous structures, antibiotic resistance, DNA similarities.

Reproduction: asexual (one parent, offspring genetically identical, e.g., binary fission, budding, vegetative propagation) vs sexual (two parents, gametes fuse, offspring genetically varied).

Human reproduction: fertilisation in the oviduct; zygote implants in uterus; placenta exchanges nutrients, oxygen and wastes between mother and fetus.

Balanced diet: carbohydrates (energy), proteins (growth and repair), fats (energy store and insulation), vitamins (A, B, C, D, E, K), minerals (calcium, iron, iodine), fibre (prevents constipation), water.

Deficiency diseases: scurvy (vitamin C), rickets (vitamin D/calcium), beriberi (vitamin B1), anaemia (iron), goitre (iodine), night blindness (vitamin A), kwashiorkor (protein).

Digestion: mechanical (teeth, churning) and chemical (enzymes). Amylase breaks starch → maltose; protease breaks proteins → amino acids; lipase breaks fats → fatty acids + glycerol. Villi in small intestine increase absorption surface area.

Pathogens: bacteria (cholera, tuberculosis), viruses (influenza, HIV/AIDS, measles), protozoa (malaria), fungi (athlete’s foot). Transmission by air, water, food, vectors, contact, blood.

Body defences: skin, mucus and cilia, stomach acid, white blood cells (phagocytes engulf; lymphocytes produce antibodies). Vaccination exposes the body to weakened antigens, producing memory cells and immunity.

Non-communicable diseases: diabetes (blood glucose control), heart disease (diet, smoking, lack of exercise), cancer (uncontrolled cell division), obesity. Risk factors include poor diet, smoking, alcohol, inactivity.

Antibiotics kill bacteria but not viruses; misuse leads to antibiotic resistance. Antiseptics are used on surfaces and skin; disinfectants on non-living objects.

First aid and hygiene: wash hands, cover wounds, sterilise equipment, use clean water; ORS (oral rehydration solution) treats dehydration from diarrhoea.

Speed = distance/time (m/s); velocity = displacement/time with direction; acceleration = change in velocity/time (m/s²). Distance–time graph slope = speed; velocity–time graph slope = acceleration, area under graph = distance.

Newton’s laws: (1) an object stays at rest or uniform motion unless acted on by a resultant force; (2) F = ma; (3) every action has an equal and opposite reaction.

Weight = mass × gravitational field strength (W = mg; g ≈ 9.8 N/kg on Earth). Mass is constant; weight changes with gravity.

Friction opposes motion between surfaces; it can be reduced by lubricants, smoothing, or using wheels/ball bearings. Air resistance and drag increase with speed and surface area.

Work = force × distance moved in direction of force (W = Fd, joules). Power = work/time (watts). Energy is the capacity to do work; measured in joules.

Kinetic energy = ½mv²; gravitational potential energy = mgh. Energy is conserved but transforms between forms; some energy dissipates as heat.

Simple machines: lever (effort × effort arm = load × load arm), pulley (fixed pulley changes direction; movable pulley halves effort), inclined plane, wedge, screw, wheel and axle.

Mechanical advantage (MA) = load/effort; velocity ratio (VR) = distance moved by effort/distance moved by load; efficiency = (useful work output / total energy input) × 100% = MA/VR × 100%.

Pressure = force/area (Pa); pressure in liquids increases with depth; upthrust equals weight of fluid displaced (Archimedes’ principle).

Light travels in straight lines at 3 × 10⁸ m/s in vacuum. Reflection: angle of incidence = angle of reflection; plane mirror forms virtual, upright, laterally inverted image of equal size.

Refraction: light bends when changing medium because speed changes. From air to glass/water it bends towards the normal; from glass/water to air it bends away. Snell’s law: n₁ sin θ₁ = n₂ sin θ₂.

Lenses: convex (converging) forms real or virtual images; concave (diverging) always forms virtual, diminished, upright images. Dispersion splits white light into a spectrum (red bends least, violet most).

Sound is a longitudinal mechanical wave: compressions and rarefactions; needs a medium; cannot travel through vacuum. Speed in air ≈ 340 m/s, faster in liquids and solids. Frequency determines pitch; amplitude determines loudness. Audible range for humans 20 Hz–20 kHz.

Electric current = rate of flow of charge (I = Q/t, amperes). Potential difference = energy per unit charge (V = W/Q, volts). Ohm’s law: V = IR for a conductor at constant temperature.

Series circuit: same current through all components; total resistance R = R₁ + R₂ + …; voltage divides. Parallel circuit: same voltage across branches; 1/R = 1/R₁ + 1/R₂ + …; current divides.

Electrical power P = VI = I²R = V²/R; energy = power × time (kWh). Fuse and circuit breaker protect against excess current; earth wire provides safety.

Magnetism and electricity: a current-carrying wire produces a magnetic field; a changing magnetic field induces a current (electromagnetic induction, Faraday). Motors use the force on a current-carrying conductor in a magnetic field; generators use induction.

Static electricity: charging by friction transfers electrons; like charges repel, unlike attract; charges reside on the surface and can be discharged by earthing.

Ecosystem = community of organisms + non-living environment interacting. Habitat = where an organism lives; niche = its role. Biotic factors: predators, food, disease; abiotic factors: light, temperature, water, soil, pH.

Food chains show energy flow: producer → primary consumer → secondary consumer → tertiary consumer. Arrows point in the direction of energy transfer. Food webs show interconnected chains.

Energy is lost at each trophic level (about 90% as heat, movement, excretion), so pyramids of energy are always upright; fewer top predators than producers.

Carbon cycle: photosynthesis removes CO₂; respiration, combustion and decomposition release it. Nitrogen cycle: nitrogen fixation, nitrification, assimilation, denitrification; bacteria are essential.

Natural resources: renewable (solar, wind, hydro, biomass, geothermal) vs non-renewable (coal, oil, natural gas, minerals). Sustainable use means using resources without depleting them for future generations.

Pollution: air (CO, SO₂, NOₓ, particulates from fossil fuels), water (sewage, fertilisers, industrial chemicals), land (plastics, pesticides). Effects include acid rain, eutrophication, global warming, ozone depletion.

Conservation: protected areas, recycling, reforestation, reducing, reusing, and using alternative energy; biodiversity is valuable for ecosystem stability and medicine.

Human population growth increases demand on resources; deforestation reduces CO₂ absorption and destroys habitats, contributing to climate change and species extinction.

Scientific method: observation → question → hypothesis (testable prediction) → experiment → data collection → analysis → conclusion; results should be reproducible and peer-reviewed.

Variables: independent (changed by experimenter), dependent (measured), controlled (kept constant). A fair test changes only the independent variable.

SI units: length metre (m), mass kilogram (kg), time second (s), temperature kelvin (K), current ampere (A), amount mole (mol), luminous intensity candela (cd).

Prefixes: kilo (×10³), centi (×10⁻²), milli (×10⁻³), micro (×10⁻⁶), nano (×10⁻⁹). Convert units before calculating.

Measurement instruments: metre rule (mm), vernier callipers (0.1 mm), micrometer (0.01 mm), thermometer, stopwatch, ammeter (series), voltmeter (parallel), balance (g), measuring cylinder (volume).

Accuracy = closeness to true value; precision = closeness of repeated readings to each other. Random errors affect precision; systematic errors shift all readings in one direction.

Significant figures and rounding: record to the precision of the instrument; read meniscus at eye level; avoid parallax error.

Lab safety: wear goggles and lab coat; never taste chemicals; heat test tubes at an angle away from people; handle glassware carefully; know the location of fire extinguisher and first-aid kit; dispose of waste properly.

Data presentation: tables with units, line graphs for continuous data (label axes, plot points, draw line of best fit), bar charts for categories; identify anomalies and calculate means.