Science and Technology Part 1 विज्ञान भाग 1

Quick summary

Every object pulls every other object. This pull is gravitation (गुरुत्वाकर्षण). It keeps the Moon around the Earth and makes things fall.

Key points

• A body moving in a circle needs a force towards the centre: centripetal force.
• Kepler 1: a planet's orbit is an ellipse with the Sun at one focus.
• Kepler 2: the Sun–planet line covers equal areas in equal times (planet is faster near the Sun).
• Kepler 3: T² ∝ r³.
• Newton's law: force ∝ product of masses and ∝ 1/(distance)².
• g is highest at the poles, lowest at the equator; it decreases with height and with depth (g = 0 at the centre).
• On the Moon, g is about 1/6 of Earth's.
• Mass stays the same everywhere; weight changes with g.

Important terms

• Free fall – falling under gravity alone.
• Acceleration due to gravity (g) – acceleration caused by Earth's pull, about 9.8 m/s².
• Escape velocity – least speed needed to leave Earth for ever (11.2 km/s).
• Weight – force with which Earth pulls a body (W = mg).

Formulas

Example

A stone of mass 2 kg on Earth (g = 9.8 m/s²): W = 2 × 9.8 = 19.6 N. On the Moon: about 19.6 ÷ 6 ≈ 3.3 N. Mass is still 2 kg.

Quick revision

• Mass: kg, scalar, same everywhere. Weight: N, vector, changes.
• G is universal; g changes from place to place.
• In vacuum, a feather and a coin fall together.
• Astronauts feel weightless because they are in free fall.

Quick summary

Scientists arranged elements in groups so their properties are easy to study. The modern periodic table arranges them by increasing atomic number.

Key points

• Döbereiner's triads: groups of three; middle element's atomic mass ≈ average of the other two (Li, Na, K). Only a few triads found.
• Newlands' octaves: every 8th element has similar properties. Worked only up to calcium.
• Mendeleev: arranged by atomic mass; left gaps for undiscovered elements (eka-aluminium = gallium, eka-silicon = germanium).
• Mendeleev's problems: no fixed place for hydrogen and isotopes; some pairs in wrong mass order (Co–Ni).
• Modern periodic law (Moseley): properties are a periodic function of atomic number.
• Modern table: 7 periods (rows), 18 groups (columns); s, p, d, f blocks.
• Elements in a group have the same number of valence electrons.

Important terms

• Period – horizontal row; same number of shells.
• Group – vertical column; same valence electrons.
• Valency – combining capacity of an atom.
• Metalloids – show properties of metals and non-metals (B, Si, As).

Key facts

Example

Sodium (Z = 11): 2, 8, 1 → period 3 (three shells), group 1 (one valence electron), valency 1.

Quick revision

• Shell capacity: 2n² (K = 2, L = 8, M = 18).
• Group 18 = noble gases, valency 0.
• Group 1 = alkali metals, group 17 = halogens.
• Isotopes have the same place because atomic number is the same.

Quick summary

In a chemical reaction, substances change into new substances. We write it as a balanced chemical equation.

Key points

• Signs of a reaction: change in colour, gas given off, precipitate, temperature change.
• A balanced equation has the same number of each atom on both sides.
• Combination: A + B → AB. Decomposition: AB → A + B.
• Displacement: a more reactive element pushes out a less reactive one.
• Double displacement: two compounds exchange ions (often a precipitate forms).
• Exothermic reactions give out heat; endothermic reactions take in heat.
• Rate of reaction increases with temperature, concentration, smaller particle size and a catalyst.
• Oxidation = gain of oxygen / loss of hydrogen; reduction = the reverse. Both together = redox.

Important terms

• Reactants / products – substances before / after the reaction.
• Precipitate – insoluble solid formed in a solution.
• Corrosion – slow damage of metals by air and moisture (rusting of iron).
• Rancidity – food fats getting oxidised, giving bad smell and taste.

Formulas

• CaO + H₂O → Ca(OH)₂ + heat (combination, exothermic)
• CaCO₃ → CaO + CO₂ (decomposition on heating)
• Fe + CuSO₄ → FeSO₄ + Cu (displacement)
• BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl (double displacement)
• CuO + H₂ → Cu + H₂O (redox)

Example

Iron nail in blue copper sulphate solution: the solution turns light green and a brown coat of copper forms on the nail, because iron is more reactive than copper.

Quick revision

• Balance only by changing coefficients, never formulas.
• Rust = hydrated iron oxide (Fe₂O₃·xH₂O).
• Prevent corrosion: paint, oil, galvanising.
• Prevent rancidity: airtight packing, nitrogen in chips packets, refrigeration.

Quick summary

Electric current produces heat and magnetism. These effects run heaters, fuses, motors and generators.

Key points

• Heating effect (Joule's law): H = I²Rt. Used in heaters, irons, bulbs, fuses.
• Heater coils use nichrome (high resistance, high melting point).
• A fuse melts and breaks the circuit when current is too high; MCB does the same job.
• Short circuit: live and neutral wires touch, current becomes very large.
• A current-carrying wire makes a magnetic field (Oersted). Direction: right-hand thumb rule.
• A solenoid with current behaves like a bar magnet.
• Motor: a coil in a magnetic field rotates when current flows (electrical → mechanical).
• Electromagnetic induction: a changing magnetic field makes current in a coil. Generator uses it (mechanical → electrical).

Important terms

• Fleming's left-hand rule – force on a conductor (motor).
• Fleming's right-hand rule – direction of induced current (generator).
• Galvanometer – detects small currents.
• AC / DC – current that changes direction / flows one way. India's AC: 50 Hz.

Formulas

Diagram in words

• Motor: rectangular coil between N and S poles, split rings (commutator) and brushes connected to a battery.
• Generator: same coil turned by an axle, connected to slip rings (AC) and brushes.

Example

A 2 Ω heater carries 5 A for 10 s: H = 5² × 2 × 10 = 500 J.

Quick revision

• Left hand = motor, right hand = generator.
• Fuse wire: low melting point, connected in the live wire.
• Split ring makes a DC motor keep turning one way.

Quick summary

Heat is energy that flows from a hotter body to a colder one. This chapter covers latent heat, specific heat and the strange behaviour of water.

Key points

• Unit of heat: joule (J); also calorie. 1 cal = 4.18 J.
• 1 calorie heats 1 g of water by 1 °C (from 14.5 °C to 15.5 °C).
• During melting or boiling the temperature stays constant; heat used then is latent heat.
• Regelation: ice melts under pressure and freezes again when pressure is removed.
• Anomalous behaviour of water: from 4 °C to 0 °C water expands instead of contracting. Water is densest at 4 °C. Shown by Hope's apparatus.
• Because of this, lakes freeze only at the top; fish survive below.
• Principle of heat exchange: heat lost by the hot body = heat gained by the cold body.

Important terms

• Specific heat capacity (c) – heat needed to raise 1 kg of a substance by 1 °C (J/kg °C).
• Latent heat of fusion – heat to melt 1 kg solid without temperature change (ice: 336 kJ/kg).
• Latent heat of vaporisation – heat to change 1 kg liquid to gas (water: 2256 kJ/kg).
• Dew point – temperature at which air becomes saturated with vapour.
• Humidity – amount of water vapour in air.

Formulas

Example

Heat to warm 2 kg water from 20 °C to 30 °C (c = 4200 J/kg °C): Q = 2 × 4200 × 10 = 84,000 J.

Quick revision

• Water has a high specific heat, so it is used in radiators and hot-water bags.
• Temperature–time graph of heating ice: flat parts = melting and boiling.
• Water pipes burst in winter because freezing water expands.

Quick summary

Light changes direction when it goes from one medium to another. This bending is refraction (अपवर्तन). It explains mirages, twinkling stars and rainbows.

Key points

• Light bends because its speed is different in different media.
• Going to a denser medium, light bends towards the normal; to a rarer medium, away from it.
• Law 1: incident ray, refracted ray and normal lie in the same plane.
• Law 2 (Snell's law): sin i / sin r = constant (refractive index).
• Atmospheric refraction: stars twinkle; Sun is seen about 2 minutes before sunrise and after sunset.
• Mirage: hot air near the road bends light, giving a false image of water.
• Dispersion: a prism splits white light into seven colours (VIBGYOR). Red bends least, violet most.
• Total internal reflection: light going from a denser to a rarer medium at more than the critical angle reflects back fully (sparkle of diamond, optical fibres).
• Rainbow: water drops refract, disperse and internally reflect sunlight.

Important terms

• Refractive index (n) – how much a medium slows and bends light.
• Normal – line perpendicular to the surface at the point of incidence.
• Spectrum – band of seven colours from white light.

Formulas

Example

Speed of light in glass = 2 × 10⁸ m/s. n = 3 × 10⁸ ÷ 2 × 10⁸ = 1.5.

Quick revision

• n: air ≈ 1.0003, water 1.33, glass 1.5, diamond 2.42.
• Higher n = optically denser = slower light.
• Visible light: about 400 nm (violet) to 700 nm (red).

Quick summary

A lens is a piece of transparent material with curved surfaces that bends light to form images. The human eye has a natural convex lens.

Key points

• Convex lens (converging): thick in the middle. Concave lens (diverging): thin in the middle.
• Light refracts twice in a lens.
• Ray rules: (1) parallel ray → through F; (2) ray through F → comes out parallel; (3) ray through O → goes straight.
• Convex lens: object beyond 2F₁ → small real inverted image; at F₁ → image at infinity; between F₁ and O → virtual, erect, magnified (magnifying glass).
• Concave lens always gives a small, virtual, erect image.
• The eye focuses near and far objects by changing the focal length of its lens (accommodation).
• Near point = 25 cm; far point = infinity.

Important terms

• Focal length (f) – distance between optical centre and principal focus.
• Power (P) – 1/f, unit dioptre (D).
• Myopia – near-sightedness; corrected by concave lens.
• Hypermetropia – far-sightedness; corrected by convex lens.
• Presbyopia – old-age difficulty in seeing near; bifocal lens.

Formulas

Diagram in words

• Draw the principal axis, lens at O, mark F₁, 2F₁, F₂, 2F₂. Use two of the three ray rules; where rays meet is the image.

Example

f = 0.5 m → P = 1/0.5 = +2 D (convex lens).

Quick revision

• Real image: inverted; virtual image: erect.
• Myopia: image forms in front of retina. Hypermetropia: behind it.
• Microscopes and telescopes use convex lenses.
• Uses of concave lens: spectacles for myopia, peepholes, torches.

Quick summary

Metallurgy is the science of getting metals from their ores and purifying them. The chapter also compares metals and non-metals.

Key points

• Metals: shiny, hard (except Na, K), malleable, ductile, good conductors, sonorous. Mercury is a liquid metal.
• Non-metals: dull, brittle, poor conductors (graphite conducts). Bromine is a liquid non-metal.
• Metals form basic oxides; non-metals form acidic oxides. Al₂O₃ and ZnO are amphoteric.
• Na and K react violently with air and water, so they are kept in kerosene.
• Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au.
• Steps of metallurgy: (1) concentration of ore, (2) extraction, (3) refining.
• Concentration methods: gravity separation, froth flotation, magnetic separation, leaching.
• Aluminium from bauxite: Bayer's / Hall's process to get alumina, then electrolysis.
• Refining: electrolytic refining (pure metal at cathode).

Important terms

• Mineral – natural compound of a metal. Ore – mineral from which metal is extracted profitably.
• Gangue – unwanted earthy impurities in the ore.
• Roasting – heating sulphide ore in air. Calcination – heating carbonate ore without air.
• Alloy – mixture of metals (brass = Cu + Zn, bronze = Cu + Sn).
• Aqua regia – 3 parts conc. HCl + 1 part conc. HNO₃; dissolves gold.

Formulas

• 2ZnS + 3O₂ → 2ZnO + 2SO₂ (roasting)
• ZnCO₃ → ZnO + CO₂ (calcination)
• ZnO + C → Zn + CO (reduction)
• Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Example

Copper does not react with dilute HCl because it is below hydrogen in the reactivity series.

Quick revision

• Cryolite lowers the melting point of alumina in electrolysis.
• Corrosion of copper: green coat. Silver: black coat (Ag₂S).
• Galvanising = coating iron with zinc.

Quick summary

Carbon forms millions of compounds because it can bond with itself and other atoms. Organic chemistry studies these compounds.

Key points

• Carbon has valency 4 (tetravalent) and forms covalent bonds by sharing electrons.
• Catenation: carbon atoms join into long chains, branches and rings.
• Carbon can form single, double and triple bonds.
• Isomerism: same molecular formula, different structures (n-butane and isobutane, C₄H₁₀).
• Hydrocarbons: alkanes (single bonds, CₙH₂ₙ₊₂), alkenes (double, CₙH₂ₙ), alkynes (triple, CₙH₂ₙ₋₂).
• A homologous series differs by –CH₂– in each step.
• Functional groups: –OH alcohol, –CHO aldehyde, >C=O ketone, –COOH carboxylic acid, –X halo.
• Reactions: combustion, oxidation, addition (hydrogenation of oils), substitution (with chlorine), esterification.

Important terms

• Saturated compound – only single C–C bonds.
• Unsaturated compound – at least one double or triple bond.
• IUPAC name – root (meth, eth, prop, but…) + bond ending (ane/ene/yne) + suffix.
• Ester – sweet-smelling compound from acid + alcohol.
• Polymer – big molecule made of repeating units (polythene).

Formulas

• CH₄ + 2O₂ → CO₂ + 2H₂O + heat
• CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O (with conc. H₂SO₄)
• CH₂=CH₂ + H₂ → CH₃–CH₃ (Ni catalyst)

Example

CH₃–CH₂–OH: 2 carbons (eth), single bonds (ane), –OH (ol) → ethanol.

Quick revision

• Diamond and graphite are allotropes of carbon.
• Ethanol can be used as a fuel (cleaner burning).
• Soap removes oil by forming micelles.
• Vinegar = 5–8% acetic acid.

Quick summary

Space missions send satellites and spacecraft beyond Earth. They help in communication, weather, defence and learning about the universe.

Key points

• Uses of space missions: TV and internet links, GPS, weather and disaster warning, defence, finding resources.
• Natural satellite: e.g. the Moon. Artificial satellite: made by humans.
• Satellite types by work: communication, weather, navigation, earth observation, military, broadcasting.
• Orbits: Low Earth Orbit (180–2000 km), Medium Earth Orbit (2000–35,780 km), High Earth Orbit (above 35,780 km). Geostationary satellites (~35,780 km) seem fixed over one place.
• Launch vehicles: PSLV and GSLV (India, ISRO).
• India's missions: Aryabhata (1975), Chandrayaan-1 (2008, found water on the Moon), Mangalyaan (2013), Chandrayaan-3 (landed near the Moon's south pole, 2023).
• Space debris: old satellites and pieces orbiting Earth; a danger to working satellites.

Important terms

• Escape velocity – 11.2 km/s from Earth's surface.
• Orbital velocity – speed needed to stay in an orbit.
• Launch vehicle – rocket that carries a satellite to its orbit.

Formulas

Example

A satellite higher up moves more slowly: v depends on 1/√(R + h), so as h increases, v decreases.

Quick revision

• ISRO = Indian Space Research Organisation (1969).
• Geostationary satellite period = 24 hours.
• GSLV for heavy satellites to higher orbits.
• Debris can be reduced by de-orbiting old satellites.