Science

Chapter 1 of Class 10 Science, "Chemical Reactions and Equations", explains what chemical reactions are, how to write and balance chemical equations, the major types of chemical reactions (combination, decomposition, displacement, double displacement, and redox), and the everyday effects of oxidation such as corrosion and rancidity.

• 1A chemical reaction is indicated by changes in state, colour, temperature, or evolution of a gas
• 2Chemical equations must be balanced to satisfy the law of conservation of mass — atoms of each element are equal on both sides
• 3Combination reactions form one product from two or more reactants; decomposition reactions are the reverse — one substance breaks into two or more
• 4Displacement reactions occur when a more reactive element displaces a less reactive one from its compound; double displacement reactions involve exchange of ions between two compounds
• 5Exothermic reactions release heat (e.g. respiration, burning of natural gas); endothermic reactions absorb energy (e.g. electrolysis of water, decomposition by heat or light)

NCERT Class 10 Science Chapter 2 covers Acids, Bases and Salts — explaining their chemical properties, the pH scale (0–14), neutralisation reactions, and important salts like baking soda, washing soda, bleaching powder, and Plaster of Paris derived from common salt.

• 1Acids turn blue litmus red and produce H⁺(aq) ions in water; bases turn red litmus blue and produce OH⁻(aq) ions in water.
• 2Acid + Metal → Salt + Hydrogen gas; Metal carbonate + Acid → Salt + Carbon dioxide + Water.
• 3Neutralisation reaction: Acid + Base → Salt + Water; e.g., NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).
• 4The pH scale (0–14) measures hydrogen ion concentration: pH 7 is neutral, below 7 is acidic, above 7 is basic. Human body functions within pH 7.0–7.8.
• 5Tooth decay begins when mouth pH drops below 5.5; toothpastes are basic to neutralise excess acid. Acid rain has pH less than 5.6.

NCERT Class 10 Science Chapter 3 covers Metals and Non-metals, explaining their physical and chemical properties, reactivity series, extraction from ores, ionic compound formation, corrosion, and alloys.

• 1Metals are lustrous, malleable, ductile, and good conductors of heat and electricity; most are solids at room temperature, with mercury being the only liquid metal.
• 2Non-metals are generally poor conductors and non-malleable; exceptions include graphite (conducts electricity) and iodine (lustrous).
• 3Metals react with oxygen to form basic oxides; amphoteric oxides like aluminium oxide (Al₂O₃) and zinc oxide react with both acids and bases.
• 4The reactivity series ranks metals from most reactive (K, Na, Ca) to least reactive (Cu, Hg, Ag, Au); a more reactive metal displaces a less reactive one from its salt solution.
• 5Metals high in the activity series (Na, Mg, Al) are extracted by electrolytic reduction; moderately reactive metals (Zn, Fe) are obtained by roasting/calcination followed by reduction with carbon.

NCERT Class 10 Science Chapter 4, Carbon and its Compounds, explains how carbon's tetravalency and catenation enable it to form millions of compounds through covalent bonding, and covers key carbon compounds including hydrocarbons, ethanol, ethanoic acid, soaps, and detergents.

• 1Carbon has a valency of four (tetravalent) and forms covalent bonds by sharing electrons with carbon or other elements such as hydrogen, oxygen, nitrogen, sulphur, and chlorine.
• 2Catenation — carbon's ability to bond with other carbon atoms — gives rise to long chains, branched chains, and ring structures, resulting in millions of stable carbon compounds.
• 3Saturated hydrocarbons (alkanes) contain only single bonds and are relatively unreactive; unsaturated hydrocarbons (alkenes, alkynes) contain double or triple bonds and are more reactive.
• 4A homologous series is a family of compounds sharing the same functional group and differing by a –CH2– unit; successive members differ by 14 u in molecular mass.
• 5Ethanol reacts with sodium to produce hydrogen gas and is dehydrated by hot concentrated H2SO4 to form ethene; ethanoic acid (acetic acid) undergoes esterification with ethanol to give sweet-smelling esters.

Life Processes are the essential maintenance functions — nutrition, respiration, transportation, and excretion — that all living organisms must carry out continuously to survive and repair their ordered internal structures.

• 1Photosynthesis in autotrophs converts CO2 and water into carbohydrates using sunlight and chlorophyll; stomata regulate gas exchange and guard cells control stomatal opening.
• 2In human digestion, salivary amylase acts on starch in the mouth, gastric glands secrete HCl and pepsin in the stomach, and the small intestine completes digestion with bile and pancreatic juice; villi absorb digested food.
• 3Aerobic respiration (in mitochondria) releases far more energy than anaerobic respiration; glucose is first broken down to pyruvate in the cytoplasm, with ATP as the universal energy currency.
• 4The human heart has four chambers enabling double circulation; oxygenated and deoxygenated blood are kept separate; haemoglobin in red blood corpuscles carries oxygen.
• 5In plants, xylem transports water and minerals upward (driven by transpiration pull and root pressure); phloem translocates photosynthesis products using ATP-driven osmotic pressure.

NCERT Class 10 Science Chapter 6 covers Control and Coordination — the mechanisms by which the nervous system and hormones enable animals and plants to detect environmental stimuli and respond appropriately through electrical impulses, reflex arcs, brain regions, and chemical signals.

• 1Neurons carry information as electrical impulses from dendrites through the cell body and axon; chemicals released at synapses bridge the gap to the next neuron or effector cell.
• 2Reflex arcs are rapid, involuntary pathways processed in the spinal cord (not the brain), allowing quick responses such as withdrawing a hand from a flame.
• 3The human brain has three regions: fore-brain (thinking, sensory areas), mid-brain/hind-brain (involuntary actions, blood pressure, salivation), and cerebellum (posture and balance).
• 4Plants show two types of movement: growth-independent (e.g., sensitive plant folding leaves via water pressure changes) and growth-dependent tropisms (phototropism, geotropism, hydrotropism, chemotropism).
• 5Auxin synthesised at the shoot tip causes unequal cell elongation, bending the plant towards light; gibberellins and cytokinins promote growth while abscisic acid inhibits it and causes leaf wilting.

NCERT Class 10 Science Chapter 7 explains how organisms reproduce using asexual methods (fission, budding, fragmentation, regeneration, vegetative propagation, spore formation) and sexual reproduction, covering flowering plants and the human reproductive system including puberty, fertilisation, and contraception.

• 1DNA copying is the fundamental event in reproduction; copies are similar but not identical, producing variations that drive evolution.
• 2Asexual reproduction modes include binary fission (Amoeba, bacteria), multiple fission (Plasmodium), budding (Hydra, yeast), fragmentation (Spirogyra), regeneration (Planaria), vegetative propagation (potato, Bryophyllum), and spore formation (Rhizopus).
• 3In flowering plants, pollen transfers from stamen to stigma (pollination), followed by fertilisation in the ovary to form a zygote that develops into a seed inside a fruit.
• 4Sperms are produced in the testes (located in the scrotum for lower temperature); eggs mature in the ovaries, with one released monthly through the fallopian tube to the uterus.
• 5The placenta — a disc embedded in the uterine wall — supplies glucose and oxygen from the mother's blood to the developing embryo and removes waste products.

Heredity is the reliable inheritance of traits from parents to offspring through genes. Gregor Johann Mendel's experiments on pea plants established the fundamental rules of inheritance, including dominant and recessive traits and independent assortment.

• 1Variations arising during reproduction can be inherited, and natural selection favours variants better suited to their environment.
• 2Mendel used pea plants with contrasting traits (tall/short, round/wrinkled seeds) to establish laws of inheritance across F1 and F2 generations.
• 3In F1 crosses, only one parental trait (dominant) appears; in F2, the ratio of dominant to recessive is approximately 3:1.
• 4Two traits (e.g., seed shape and seed colour) are inherited independently of each other, producing new combinations in offspring.
• 5Genes are carried on chromosomes; each cell has two copies of each chromosome, one from each parent, while germ cells carry only one copy.

NCERT Class 10 Science Chapter 9 covers Light — Reflection and Refraction, explaining the laws of reflection, image formation by spherical mirrors and lenses, refraction, refractive index, and the power of lenses.

• 1The angle of incidence equals the angle of reflection; the incident ray, normal, and reflected ray all lie in the same plane.
• 2For spherical mirrors, R = 2f — the radius of curvature is twice the focal length; the mirror formula is 1/v + 1/u = 1/f.
• 3A concave mirror forms real and inverted images for objects beyond F, but a virtual, erect, and enlarged image when the object is between the pole and focus; convex mirrors always form virtual, erect, and diminished images.
• 4Refraction is the change in direction of light when it travels obliquely from one transparent medium to another; Snell's law states sin i / sin r = constant (refractive index).
• 5The refractive index of a medium equals the ratio of the speed of light in vacuum (3×10⁸ m/s) to the speed of light in that medium; diamond has the highest refractive index (2.42) among common materials.

Class 10 Science Chapter 10 covers the human eye's structure and defects of vision, dispersion of white light through a prism, atmospheric refraction phenomena like twinkling of stars, and why the sky appears blue due to scattering of light.

• 1The human eye uses a crystalline lens and ciliary muscles to adjust focal length, enabling accommodation for objects from 25 cm (near point) to infinity (far point).
• 2Myopia (near-sightedness) is corrected with a concave lens; hypermetropia (far-sightedness) is corrected with a convex lens; presbyopia (age-related) often requires bi-focal lenses.
• 3A glass prism splits white light into seven colours — Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR) — because different colours bend through different angles.
• 4A rainbow is formed when water droplets in the atmosphere refract, internally reflect, and disperse sunlight, and is always seen in the direction opposite the Sun.
• 5Stars twinkle due to continuous atmospheric refraction of starlight, while planets do not twinkle because they appear as extended sources whose variations average out to zero.

NCERT Class 10 Science Chapter 11 covers Electricity — the flow of electric charge through conductors, governed by Ohm's law (V = IR), resistance, series and parallel circuits, Joule's heating effect (H = I²Rt), and electric power (P = VI).

• 1Electric current I = Q/t is measured in amperes (A); 1 coulomb of charge equals the charge of approximately 6 × 10¹⁸ electrons.
• 2Ohm's law: potential difference V across a conductor is directly proportional to current I at constant temperature, expressed as V = IR.
• 3Resistance R = ρl/A; resistivity ρ (in Ω m) depends on the material — metals have resistivity 10⁻⁸ to 10⁻⁶ Ω m, insulators 10¹² to 10¹⁷ Ω m.
• 4In a series circuit, equivalent resistance Rs = R1 + R2 + R3 and the same current flows through all resistors; in a parallel circuit, 1/Rp = 1/R1 + 1/R2 + 1/R3 and the same potential difference appears across each resistor.
• 5Joule's law of heating: H = I²Rt — heat produced is proportional to the square of current, resistance, and time; this principle powers electric heaters, irons, and fuses.

Electric current produces a magnetic field around a conductor; a current-carrying conductor placed in a magnetic field experiences a force. These magnetic effects of electric current are the basis of electromagnets, electric motors, and domestic electrical safety systems.

• 1A current-carrying conductor produces a magnetic field; field lines around a straight wire form concentric circles whose direction is given by the right-hand thumb rule
• 2Magnetic field strength increases with current and decreases with distance from the conductor
• 3A solenoid carrying current behaves like a bar magnet, with uniform parallel field lines inside; placing soft iron inside creates an electromagnet
• 4Fleming's left-hand rule determines the direction of force on a current-carrying conductor in a magnetic field — thumb, forefinger, and middle finger mutually perpendicular represent motion, field, and current respectively
• 5Indian domestic supply is 220 V AC at 50 Hz; circuits use red (live), black (neutral), and green (earth) wires, with separate 15 A and 5 A circuits for high- and low-power appliances

NCERT Class 10 Science Chapter 13 'Our Environment' explains how ecosystems function through food chains, energy flow, biological magnification of pesticides, ozone layer depletion by CFCs, and the environmental impact of biodegradable versus non-biodegradable waste.

• 1An ecosystem consists of biotic components (living organisms) and abiotic components (temperature, rainfall, wind, soil, minerals); examples include forests, ponds, gardens, and crop-fields.
• 2Organisms are classified as producers (green plants and certain bacteria using photosynthesis), consumers (herbivores, carnivores, omnivores, parasites), and decomposers (bacteria and fungi that break down dead matter).
• 3Only about 10% of energy at one trophic level is transferred to the next; green plants capture only about 1% of sunlight, which limits food chains to three or four trophic levels.
• 4Biological magnification occurs when non-degradable pesticide chemicals accumulate progressively at each trophic level, reaching maximum concentration in humans at the top of the food chain.
• 5The ozone layer (O₃) shields Earth from harmful UV radiation; synthetic chemicals called CFCs (used in refrigerants and fire extinguishers) caused a sharp drop in ozone levels from the 1980s, leading to a 1987 UNEP agreement to freeze CFC production.