A chapter-wise handbook of key facts, definitions and concepts from the Class 7 NCERT Science textbook (Curiosity, 2026-27 edition). This handbook is now complete, covering all 12 chapters of the book, added as each chapter’s Solutions/Extra Questions/Revision Notes were published.
See also: Class 7 Science NCERT Book
Chapter 1: The Ever-Evolving World of Science
- Core idea: science is an ongoing process of curiosity, questioning and exploration — not a fixed set of facts.
- Cause and effect: recognising patterns/causes lets us explain and predict events (e.g. rain → wet ground).
- Sour fruits: sourness comes from natural acids (e.g. citric acid); acid content and ripeness both affect taste.
- Haldi + soap: soap is basic/alkaline and reacts with turmeric’s pigment, turning a stain reddish — a preview of acid-base chemistry.
- Themes previewed for later chapters: conductors/insulators, reversible vs permanent changes, heat speeding up changes, animal life processes, photosynthesis, light/shadows/eclipses.
See full Chapter 1 Solutions.
Chapter 2: Exploring Substances – Acidic, Basic and Neutral
- Litmus paper (from lichen extract): acids turn blue litmus red; bases turn red litmus blue; neutral substances cause no change.
- Natural indicators: turmeric (red in base, no change in acid/neutral); red rose extract (red in acid, green in base).
- Olfactory indicators: onion, vanilla — change smell with acid/base exposure.
- Acidic examples: lemon (citric acid), tamarind (tartaric acid), vinegar (acetic acid). Basic examples: soap, baking soda, lime water, washing powder. Neutral: tap water, sugar solution, salt solution.
- Neutralisation: mixing acid + base cancels out each other’s character, moving toward neutral (used for acidic soil, industrial waste, antacids).
See full Chapter 2 Solutions.
Chapter 3: Electricity – Circuits and their Components
- A circuit is a closed path for electric current; it must be complete for a lamp/device to work.
- A cell has two terminals; connecting multiple cells in series (correct polarity) adds their voltages (e.g., 1.5V times 3 = 4.5V).
- A switch is a device that opens or closes a circuit; ON = closed circuit, OFF = open circuit.
- Conductors (allow current to flow): metals like copper, aluminium, iron; also graphite (a non-metal conductor).
- Insulators (block current flow): wood, plastic, glass, paper, wax, rubber.
- Wires are insulated with plastic/rubber coating for safety, to prevent short circuits and electric shocks.
- LEDs only light up when connected with correct polarity (unlike incandescent lamps, which work either way).
- Common circuit symbols: cell (long and short parallel lines), battery (multiple cells), switch, bulb/LED, connecting wire.
Chapter 4: The World of Metals and Non-metals
- Metals are generally lustrous, malleable, ductile, sonorous, and good conductors of heat and electricity (e.g. copper, aluminium, iron, gold, sodium).
- Non-metals are generally non-lustrous, brittle, poor conductors, and often gaseous (e.g. sulphur, oxygen, nitrogen, carbon); graphite is an exception, being a non-metal that conducts electricity.
- Metal oxides are generally basic (turn red litmus blue); non-metal oxides are generally acidic (turn blue litmus red).
- Rusting of iron requires both air and water together; removing either prevents rusting.
- Sodium is highly reactive and is stored in kerosene oil for safety.
- Copper is preferred for boiling-water vessels since it conducts heat well and resists corrosion better than iron.
- Protective coatings like zinc (galvanisation) prevent iron from rusting by blocking air and moisture.
Chapter 5: Changes Around Us – Physical and Chemical
- A physical change only alters shape, size, or state; no new substance is formed, and it is often reversible.
- A chemical change forms new substance(s) with different properties and is generally irreversible.
- Reversible changes (melting ice, dissolving sugar) can be undone; irreversible changes (rusting, burning, ripening) cannot.
- Combustion requires three things: a combustible substance (fuel), oxygen, and reaching the ignition temperature.
- Ignition temperature is the minimum temperature at which a substance catches fire.
- Some processes, like burning a candle, involve both physical change (melting/evaporating wax) and chemical change (burning wax vapour) together.
- Lime water turns milky when carbon dioxide gas passes through it (forms calcium carbonate) – a standard test for CO2.
- Rusting of iron and curdling of milk are classic chemical changes; magnesium oxide (from burning magnesium) is basic in nature.
Chapter 6: Adolescence – A Stage of Growth and Change
- Adolescence is the transitional stage between childhood and adulthood (roughly ages 10-19), marked by the onset of puberty.
- Hormones (estrogen in girls, testosterone in boys) drive physical changes (secondary sexual characteristics) and also influence emotions.
- Physical changes only in boys: voice change, moustache/facial hair growth. Only in girls: breast development, menstruation. Common to both: pimples, pubic and armpit hair growth.
- Adolescence also brings emotional and behavioural changes: mood swings, desire for independence, peer pressure, identity exploration.
- A balanced diet with iron and calcium is essential during adolescence; iron deficiency can cause anaemia, especially in girls due to menstrual blood loss.
- Goitre (thyroid enlargement from iodine deficiency) is different from the normal growth of the voice box (Adams apple) in boys during puberty.
- Proper menstrual hygiene and responsible social media habits are important health and safety practices during adolescence.
Chapter 7: Heat Transfer in Nature
- Three modes of heat transfer: conduction (in solids, particle-to-particle, no particle movement), convection (in liquids/gases, heated particles physically move), and radiation (no medium needed, e.g. heat from the Sun or fire).
- Good conductors: metals like steel and aluminium. Poor conductors (insulators): wood, plastic, bakelite, air.
- Hot air/liquid becomes lighter and rises; cooler, denser air/liquid sinks – this circulating movement is convection.
- Sea breeze (day): cooler air flows from sea to land. Land breeze (night): cooler air flows from land to sea. Water bodies moderate nearby temperatures since water heats and cools more slowly than land.
- Infiltration: water seeps through soil/rock into the ground and gets stored in aquifers. Seepage rate: gravel (fastest) greater than sand greater than clay (slowest), based on particle/pore size.
- The water cycle (evaporation, condensation, precipitation) continuously redistributes and replenishes water on Earth.
Chapter 8: Measurement of Time and Motion
- Before mechanical clocks, time was measured using sundials, water clocks, hourglasses, and candle clocks.
- Speed = Distance divided by Time. To convert km/h to m/s, multiply by 5/18; to convert m/s to km/h, multiply by 18/5.
- Uniform motion: equal distances covered in equal time intervals (constant speed). Non-uniform motion: unequal distances in equal time intervals (changing speed) – the more common type in daily life.
- Average speed = Total distance divided by Total time taken, applicable even for non-uniform motion.
Chapter 9: Life Processes in Animals
- Digestion begins in the mouth with salivary amylase breaking down starch; iodine test detects starch (blue-black colour).
- Rumination: cud-chewing in cows and other ruminants, aided by a multi-chambered stomach and gut microbes, for efficient digestion of fibrous plant matter.
- Breathing (mechanical inhale/exhale) vs respiration (cellular energy release using oxygen) are distinct processes.
- Air pathway: nostrils → nasal passages → windpipe → alveoli (gas exchange); ribcage protects lungs; diaphragm drives inhalation/exhalation.
- Inhaled air is oxygen-rich; exhaled air is carbon-dioxide-rich. Lime water turns milky in presence of CO2 — used to test exhaled air.
Chapter 10: Life Processes in Plants
- Photosynthesis: CO2 + Water –(sunlight+chlorophyll)–> Glucose + Oxygen; occurs in green parts of the plant, needs light.
- Glucose is stored as starch; iodine test (blue-black) confirms starch.
- Stomata (leaf pores) allow gas exchange; xylem transports water/minerals from roots upward.
- Respiration: Glucose + Oxygen → CO2 + Water + Energy; occurs in all living cells, all the time.
- Lime water turns milky with CO2 — used to show plants/seeds respire.
Chapter 11: Light: Shadows and Reflections
- Luminous objects produce their own light (Sun, stars); non-luminous objects (Moon, planets) are seen only by reflecting light.
- Light travels in a straight line (rectilinear propagation) and cannot bend around obstacles.
- Materials: transparent (clear view, nearly all light passes — glass, water), translucent (blurred view, partial light — butter paper), opaque (no view, blocks all light — wood, metal).
- Shadow formation needs a light source, an opaque object, and a screen; shadow is larger/blurrier when the object is closer to the source, smaller/sharper when closer to the screen.
- Shadow length is shortest around noon (Sun overhead) and longest in early morning/late evening (Sun near horizon).
- Reflection: smooth surfaces give regular (clear) reflection; rough surfaces give diffuse reflection/scattering.
- Plane mirror image: virtual, erect, same size as object, laterally inverted (left-right reversed, not up-down); image distance behind mirror = object distance in front.
- Pinhole camera forms a small, real, inverted image because light rays cross over at the pinhole.
- Periscope: two plane mirrors at 45° to the tube redirect light through two 90° turns, used to see over/around obstacles.
Chapter 12: Earth, Moon and the Sun
- Rotation (Earth spinning on its axis, ~24 hours) causes day and night and the apparent east-to-west motion of the Sun and stars; revolution (Earth orbiting the Sun, ~365 days) combined with the ~23.5° axial tilt causes the seasons, not distance from the Sun.
- Pole Star appears nearly fixed since it lies near Earth’s rotational axis; other stars appear to rise about 4 minutes earlier each night, shifting by a full day over a year.
- Equinoxes (~21 March, ~22/23 September): day and night close to equal everywhere; solstices: maximum tilt effect, extreme day/night lengths especially near the poles.
- Solar eclipse: Moon between Sun and Earth (new Moon), small shadow (umbra), narrow visibility, needs eye protection. Lunar eclipse: Earth between Sun and Moon (full Moon), large shadow, wide visibility, safe to view; Moon often looks reddish (“blood moon”).
- Moon appears to match the Sun’s size in the sky because apparent size depends on both actual size and distance — the Sun is roughly 400 times wider than the Moon but also roughly 400 times farther away.
See full Chapter 12 Solutions.
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