Class 10 Science Notes (Latest CBSE Syllabus) on Padhaiwise

Class 10 Science Notes Chapter 1 — Chemical Reactions and Equations

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 1 — Chemical Reactions and Equations#

Signs of a chemical reaction#

A chemical reaction forms new substances. You can tell one has happened from:

a change in state
a change in colour
evolution of a gas
a change in temperature
formation of a precipitate

Example: magnesium ribbon burns with a dazzling white flame and forms white magnesium oxide powder.

$$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$

Chemical equations#

Reactants are written on the left, products on the right, with an arrow between them.
Balanced equation — the number of atoms of each element is the same on both sides. This follows the law of conservation of mass: mass is neither created nor destroyed in a reaction.
Balance by changing the coefficients in front of formulae, never the subscripts inside them.
States: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution. Conditions such as heat, pressure or a catalyst are written above or below the arrow.

$$3\text{Fe(s)} + 4\text{H}_2\text{O(g)} \rightarrow \text{Fe}_3\text{O}_4\text{(s)} + 4\text{H}_2\text{(g)}$$

Types of chemical reactions#

Type	Pattern	Example
Combination	$A + B \rightarrow AB$	$\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2$
Decomposition	$AB \rightarrow A + B$	$\text{CaCO}_3 \xrightarrow{\text{heat}} \text{CaO} + \text{CO}_2$
Displacement	$A + BC \rightarrow AC + B$	$\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}$
Double displacement	$AB + CD \rightarrow AD + CB$	$\text{Na}_2\text{SO}_4 + \text{BaCl}_2 \rightarrow \text{BaSO}_4 + 2\text{NaCl}$

Combination reactions#

Quick lime + water: $\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2$ + heat. Calcium oxide (quick lime) forms calcium hydroxide (slaked lime). A solution of slaked lime is used for whitewashing: it reacts slowly with CO₂ in air to form a shiny coat of calcium carbonate.
Burning of coal: $\text{C} + \text{O}_2 \rightarrow \text{CO}_2$
Formation of water: $2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$

Decomposition reactions#

They need energy, given as heat, light or electricity.

Class 10 Science Notes Chapter 2 — Acids, Bases and Salts

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 2 — Acids, Bases and Salts#

Indicators#

Indicator	In acid	In base
Blue litmus	Red	No change
Red litmus	No change	Blue
Methyl orange	Red	Yellow
Phenolphthalein	Colourless	Pink
Turmeric	No change	Reddish-brown

Litmus is a natural indicator, extracted from lichen. Other natural indicators: turmeric, red cabbage, coloured petals (hydrangea, petunia, geranium).
Olfactory indicators change smell. Onion and vanilla lose their smell in a base. Clove oil also loses its smell in a base.
A curry stain (turmeric) on cloth turns reddish-brown with soap (a base), and turns yellow again when rinsed with plenty of water.

Reactions of acids and bases#

Reaction	General equation
Acid + metal	Salt + hydrogen gas
Base + metal (Zn, Al)	Salt + hydrogen gas
Acid + metal carbonate / hydrogencarbonate	Salt + CO₂ + water
Acid + base (neutralisation)	Salt + water
Acid + metal oxide	Salt + water
Base + non-metal oxide	Salt + water

$$\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2$$

Class 10 Science Notes Chapter 3 — Metals and Non-metals

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 3 — Metals and Non-metals#

Physical properties#

Property	Metals	Non-metals
Lustre	Shiny (metallic lustre)	Dull
Hardness	Generally hard	Generally soft
Malleable (beaten into sheets)	Yes — gold and silver most	No (brittle)
Ductile (drawn into wires)	Yes — gold most	No
Conduct heat and electricity	Good — silver and copper best	Poor
Sonorous (ringing sound)	Yes (school bells)	No
State at room temperature	Solid (except mercury)	Solid, liquid (bromine) or gas

Exceptions:

Class 10 Science Notes Chapter 4 — Carbon and its Compounds

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 4 — Carbon and its Compounds#

Covalent bonding#

Carbon has atomic number 6 (2, 4): 4 valence electrons. It can neither lose 4 nor gain 4 electrons easily, so it shares electrons.
Covalent bond — a bond formed by sharing a pair of electrons. A single bond shares 1 pair, a double bond 2 pairs, a triple bond 3 pairs.
Examples: H₂ (H–H, single), O₂ (O=O, double), N₂ (N≡N, triple), CH₄ (four C–H single bonds).
Covalent compounds have low melting and boiling points (weak forces between molecules) and are poor conductors of electricity (no ions).

Allotropes of carbon#

Allotrope	Structure	Properties
Diamond	Each C bonded to 4 others in a rigid 3-D network	Hardest natural substance; does not conduct
Graphite	Each C bonded to 3 others in hexagonal layers; layers slide	Smooth, slippery; good conductor
Fullerene (C-60)	Carbon atoms in the shape of a football	Named after Buckminster Fuller

Why carbon forms so many compounds#

Catenation — carbon bonds with other carbon atoms to form long chains, branches and rings.
Tetravalency — with a valency of 4, it bonds with other carbon atoms and with H, O, N, S, Cl and others.

The C–C bond is strong, so these compounds are stable.

Class 10 Science Notes Chapter 5 — Life Processes

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 5 — Life Processes#

Life processes are the basic functions that keep an organism alive: nutrition, respiration, transportation and excretion. Multicellular organisms need specialised tissues for these, since diffusion alone is too slow.

Nutrition#

Type	Meaning	Examples
Autotrophic	Makes its own food from simple inorganic substances (CO₂, water) using sunlight	Green plants, some bacteria
Heterotrophic	Depends on others for food	Animals, fungi

Heterotrophs take food in different ways: breaking it down outside the body and absorbing it (fungi like bread mould, yeast, mushrooms), taking in whole food and digesting it inside (most animals), or living on a host (parasites like cuscuta, ticks, lice, tapeworms).

Class 10 Science Notes Chapter 6 — Control and Coordination

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 6 — Control and Coordination#

Animals coordinate their activities with the nervous system and hormones. Plants use only hormones.

Nervous tissue#

Receptors — specialised tips of nerve cells that detect information from the environment (in the sense organs). For example, gustatory receptors detect taste and olfactory receptors detect smell.
Neuron (nerve cell) — the unit of the nervous system.

Path of a nerve impulse:
dendrite → cell body → axon → nerve ending → synapse → next neuron or muscle

Class 10 Science Notes Chapter 7 — How do Organisms Reproduce?

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 7 — How do Organisms Reproduce?#

Why reproduce#

Reproduction is not needed to keep one individual alive, but it keeps the species going.
The basic event is DNA copying, along with making extra cell apparatus. DNA holds the information for making proteins, and so for the body design.
Copying is never perfect, so it produces small variations. Variations help some individuals survive when the environment changes (for example, heat-resistant bacteria when water gets warmer). Variation is useful for the survival of the species, not necessarily for the individual.

Asexual reproduction#

A new organism comes from a single parent. The offspring are almost identical to the parent.

Class 10 Science Notes Chapter 8 — Heredity

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 8 — Heredity#

Variation and heredity#

Heredity — the passing of traits from parents to offspring.
Variation — differences between individuals of a species.
Asexual reproduction gives very little variation (only small copying errors in DNA). Sexual reproduction gives much more variation, because it combines DNA from two parents.
Variations build up over generations. Some help survival in a changing environment; these individuals are selected by nature.

Inherited traits#

A child shares basic features with the parents but is not identical to them.
Each trait is influenced by both the father’s and the mother’s DNA, so every child has two versions of each trait.

Mendel’s experiments#

Gregor Johann Mendel (1822–1884) worked with garden peas (Pisum sativum), using contrasting traits: round/wrinkled seeds, tall/short plants, violet/white flowers, yellow/green seeds. He counted the offspring of each type in every generation.

Class 10 Science Notes Chapter 9 — Light: Reflection and Refraction

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 9 — Light: Reflection and Refraction#

Reflection#

Laws of reflection:

The angle of incidence equals the angle of reflection ($\angle i = \angle r$).

The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.

These laws hold for all reflecting surfaces, including curved ones.

Plane mirror image: virtual, erect, the same size as the object, as far behind the mirror as the object is in front, and laterally inverted.

Class 10 Science Notes Chapter 10 — The Human Eye and the Colourful World

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 10 — The Human Eye and the Colourful World#

The human eye#

Part	Function
Cornea	Thin transparent front membrane; most of the refraction happens at its outer surface
Iris	Dark muscular diaphragm that controls the size of the pupil
Pupil	Opening that controls how much light enters (small in bright light, large in dim light)
Eye lens	Fine-adjusts the focal length to focus on the retina; forms a real, inverted image
Ciliary muscles	Change the curvature, and so the focal length, of the eye lens
Retina	Light-sensitive screen with light-sensitive cells; sends electrical signals
Optic nerve	Carries signals from the retina to the brain, which sees the image upright

Power of accommodation — the eye lens’s ability to change its focal length.
- Distant object: ciliary muscles relax, the lens gets thinner, and its focal length increases.
- Near object: ciliary muscles contract, the lens gets thicker, and its focal length decreases.
Near point (least distance of distinct vision) of a normal adult eye: 25 cm. Far point: infinity.
Cataract — the lens becomes milky and cloudy, causing partial or complete loss of vision. It is treated by surgery.

Defects of vision#

Defect	Can see clearly	Image forms	Causes	Corrected with
Myopia (near-sightedness)	Near objects only	In front of the retina	Eyeball too long, or lens too curved	Concave lens
Hypermetropia (far-sightedness)	Distant objects only; near point is beyond 25 cm	Behind the retina	Eyeball too short, or focal length too long	Convex lens
Presbyopia	Not near objects (with age)	Behind the retina	Ciliary muscles weaken and the lens loses flexibility	Convex lens; bifocal lens if both defects

A bifocal lens has a concave upper part (distant vision) and a convex lower part (near vision).
Defects can also be corrected with contact lenses or surgery.
Eye donation: one pair of eyes can give vision to up to four people with corneal blindness. Eyes must be removed within 4–6 hours of death.

Refraction through a prism#

A prism has two triangular bases and three rectangular faces. The angle between two side faces is the angle of the prism.
Light bends towards the base of the prism.
Angle of deviation — the angle between the incident ray (extended) and the emergent ray.

Dispersion#

Dispersion — splitting of white light into its colours by a prism.

Class 10 Science Notes Chapter 11 — Electricity

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 11 — Electricity#

Electric current#

$$I = \frac{Q}{t}$$

Electric current — the rate of flow of charge. In metal wires, the charges that move are electrons.
SI unit: ampere (A). 1 A = 1 C/s. Smaller units: 1 mA = 10⁻³ A, 1 μA = 10⁻⁶ A.
SI unit of charge: coulomb (C). Charge of an electron = $1.6 \times 10^{-19}$ C, so 1 C is the charge of about $6 \times 10^{18}$ electrons.
Conventional current flows from positive to negative, opposite to the flow of electrons.
Ammeter measures current. It is connected in series and has low resistance.

Potential difference#

$$V = \frac{W}{Q}$$

Potential difference — work done to move a unit charge from one point to another.
SI unit: volt (V). 1 V = 1 J/C. A cell (or battery) keeps up the potential difference by chemical action.
Voltmeter measures potential difference. It is connected in parallel and has high resistance.

Circuit symbols#

Component	Symbol
Electric cell	─\|‖─ (long line +)
Battery	several cells in series
Plug key / switch (open, closed)	─( )─ , ─(•)─
Wire joint / crossing without joint	dot at the joint / wires crossing
Bulb	⊗ in a circle
Resistor	─///─
Variable resistor (rheostat)	resistor with an arrow
Ammeter / voltmeter	Ⓐ / Ⓥ (circles)

Ohm’s law#

At constant temperature, the current through a metal wire is directly proportional to the potential difference across it:

Class 10 Science Notes Chapter 12 — Magnetic Effects of Electric Current

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 12 — Magnetic Effects of Electric Current#

Hans Christian Oersted (1820) found that a current in a wire deflects a compass needle. This showed that electricity and magnetism are linked.
A compass needle is a small bar magnet. Its north-seeking end is its north pole.

Magnetic field and field lines#

Magnetic field — the region around a magnet where its force can be felt. It has both size and direction.
Field lines show the field. The direction is the way the north pole of a compass would move.

Properties of magnetic field lines:

Class 10 Science Notes Chapter 13 — Our Environment

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science Notes Chapter 13 — Our Environment#

Ecosystem#

Ecosystem — all the living organisms in an area, together with the non-living parts of their environment, interacting with each other.
- Biotic components: plants, animals, microorganisms.
- Abiotic components: temperature, rainfall, wind, soil, minerals.
Natural ecosystems: forests, ponds, lakes. Human-made (artificial) ecosystems: gardens, crop fields, an aquarium.

Component	Role	Examples
Producers	Make food from sunlight by photosynthesis (autotrophs)	Green plants, blue-green algae
Consumers	Eat producers or other consumers	Herbivores, carnivores, omnivores, parasites
Decomposers	Break down dead remains and waste into simple substances, returning nutrients to the soil	Bacteria and fungi

Without decomposers, dead matter would pile up and nutrients would never return to the soil.

Class 10 Science — All Formulas (Quick Revision)

Mon, 01 Jan 0001 00:00:00 +0000

Class 10 Science — All Formulas#

Every formula, rule and key fact in the latest NCERT Class 10 Science book.

Light — reflection and refraction#

Formulas#

Quantity	Formula
Radius of curvature	$R = 2f$
Mirror formula	$\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$
Magnification (mirror)	$m = \dfrac{h'}{h} = -\dfrac{v}{u}$
Lens formula	$\dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f}$
Magnification (lens)	$m = \dfrac{h'}{h} = \dfrac{v}{u}$
Snell’s law	$\dfrac{\sin i}{\sin r} = \text{constant}$
Absolute refractive index	$n_m = \dfrac{c}{v}$
Relative refractive index	$n_{21} = \dfrac{v_1}{v_2}$
Power of a lens	$P = \dfrac{1}{f}$
Lenses in contact	$P = P_1 + P_2 + P_3 + \cdots$

Notes on the formulas#

Formula	Explanation and notes
Radius of curvature	$R$ = radius of curvature, $f$ = focal length. Holds for spherical mirrors of small aperture.
Mirror formula	$u$ = object distance, $v$ = image distance, $f$ = focal length, all measured from the pole. Has a + sign.
Magnification (mirror)	$h$ = object height, $h'$ = image height. Has a minus sign.
Lens formula	Distances measured from the optical centre. Has a − sign.
Magnification (lens)	No minus sign.
Snell’s law	$i$ = angle of incidence, $r$ = angle of refraction. The constant is the refractive index of medium 2 with respect to medium 1, for a given pair of media and colour of light.
Absolute refractive index	$c$ = speed of light in vacuum ($3 \times 10^8$ m/s), $v$ = speed of light in the medium. No unit.
Relative refractive index	$v_1$, $v_2$ = speed of light in medium 1 and medium 2. Higher $n$ means optically denser.
Power of a lens	$f$ must be in metres. Unit: dioptre (D); 1 D is the power of a lens with $f$ = 1 m.
Lenses in contact	Net power is the sum of the individual powers, with signs.

Laws#

Law	Statement
Reflection 1	$\angle i = \angle r$
Reflection 2	Incident ray, normal and reflected ray lie in the same plane
Refraction 1	Incident ray, refracted ray and normal lie in the same plane
Refraction 2 (Snell’s law)	$\dfrac{\sin i}{\sin r}$ is constant for a given pair of media and colour of light
Rarer → denser	Light bends towards the normal
Denser → rarer	Light bends away from the normal

New Cartesian sign convention#

Quantity	Sign
Object position	Always on the left, so $u$ is always negative
Distances measured from	Pole (mirror) or optical centre (lens)
Along incident light (right)	Positive
Against incident light (left)	Negative
Height above the principal axis	Positive
Height below the principal axis	Negative

Mirror and lens signs#

	Concave mirror	Convex mirror	Convex lens	Concave lens
Type	Converging	Diverging	Converging	Diverging
Focal length $f$	Negative	Positive	Positive	Negative
Power $P$	—	—	Positive	Negative
Real image possible?	Yes	No	Yes	No

Magnification	Meaning
$m$ negative	Real, inverted image
$m$ positive	Virtual, erect image
$\lvert m \rvert > 1$	Enlarged
$\lvert m \rvert < 1$	Diminished

Image formation — concave mirror and convex lens#

Positions in brackets are for the lens (F₁, 2F₁ and O in place of F, C and P).