Class 7 — Notes 📒

Key points, definitions and digest answers for SSC & CBSE Board — Class 7

Mathematics

Chapter 1 — Integers

📌 Key Points
  • Integers: all positive numbers, negative numbers and zero: ...−3, −2, −1, 0, 1, 2, 3...
  • Adding two negative integers gives a negative integer. Example: (−3) + (−5) = −8
  • Adding a positive and negative integer: subtract and keep sign of larger. Example: (−8) + 5 = −3
  • Subtraction: a − (−b) = a + b. Example: 5 − (−3) = 5 + 3 = 8
  • Product of two positive integers = positive
  • Product of two negative integers = positive
  • Product of one positive and one negative = negative
  • Division follows the same sign rules as multiplication
  • Commutative: a + b = b + a, a × b = b × a
  • Associative: (a+b)+c = a+(b+c), (a×b)×c = a×(b×c)
  • Distributive: a × (b + c) = a×b + a×c
✅ Digest Answers
Q. Find: (−4) × (−5) × (−2)
(−4) × (−5) = 20, then 20 × (−2) = −40
Rule: odd number of negative signs → negative result
Q. What is the additive inverse of −7?
Additive inverse of −7 is +7, because (−7) + 7 = 0
Q. Simplify: (−36) ÷ (−4)
Negative ÷ Negative = Positive → (−36) ÷ (−4) = 9
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Mathematics

Chapter 2 — Fractions and Decimals

📌 Key Points
  • Proper fraction: numerator < denominator. Example: 3/5
  • Improper fraction: numerator > denominator. Example: 7/3
  • Mixed fraction: whole number + proper fraction. Example: 2¹/₃
  • Multiplying fractions: multiply numerators and denominators separately
  • Dividing fractions: multiply by the reciprocal of divisor
  • To multiply decimals: multiply as whole numbers, then place decimal point
  • Multiplying decimal by 10, 100, 1000: shift decimal point right by 1, 2, 3 places
  • Dividing decimal by 10, 100, 1000: shift decimal point left by 1, 2, 3 places
✅ Digest Answers
Q. Find: 3/5 × 2/7
= (3×2)/(5×7) = 6/35
Q. Find: 4/5 ÷ 2/3
= 4/5 × 3/2 = 12/10 = 6/5 = 1.2
Q. Find: 2.5 × 1.4
25 × 14 = 350. Two decimal places total → 3.50
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Mathematics

Chapter 6 — Triangles and Its Properties

📌 Key Points
  • Sum of all angles of a triangle = 180°
  • Exterior angle = sum of two opposite interior angles
  • Equilateral triangle: all sides equal, all angles = 60°
  • Isosceles triangle: two sides equal, angles opposite equal sides are equal
  • Scalene triangle: all sides different
  • Median: line from vertex to midpoint of opposite side
  • Altitude: perpendicular from vertex to opposite side
  • Pythagoras theorem: in right triangle, hypotenuse² = base² + height²
  • Triangle inequality: sum of any two sides > third side
✅ Digest Answers
Q. Two angles of a triangle are 60° and 80°. Find the third angle.
Sum of angles = 180°. Third angle = 180° − 60° − 80° = 40°
Q. Find hypotenuse if base = 3 cm and height = 4 cm.
Hypotenuse² = 3² + 4² = 9 + 16 = 25. Hypotenuse = √25 = 5 cm
Q. What is an exterior angle of a triangle?
An exterior angle is formed when a side of a triangle is extended. It equals the sum of the two non-adjacent interior angles (remote interior angles).
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Mathematics

Chapter 11 — Perimeter and Area

📌 Key Formulas
  • Square: Perimeter = 4a, Area = a²
  • Rectangle: Perimeter = 2(l+b), Area = l × b
  • Triangle: Area = ½ × base × height
  • Parallelogram: Area = base × height
  • Circle: Circumference = 2πr, Area = πr² (π = 22/7 or 3.14)
  • 1 m² = 10,000 cm², 1 cm² = 100 mm²
  • Perimeter: total boundary length
  • Area: region covered inside the boundary
✅ Digest Answers
Q. Find area of triangle with base 8 cm and height 5 cm.
Area = ½ × 8 × 5 = 20 cm²
Q. Find circumference of circle with radius 7 cm.
Circumference = 2πr = 2 × 22/7 × 7 = 44 cm
Q. Find area of circle with radius 14 cm.
Area = πr² = 22/7 × 14 × 14 = 22 × 28 = 616 cm²
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Science

Chapter 1 — Nutrition in Plants

📌 Key Points
  • Nutrition: process of obtaining and using food for energy and growth
  • Autotrophs: organisms that make their own food. Example: plants (green)
  • Heterotrophs: organisms that depend on others for food. Example: animals, fungi
  • Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll)
  • Chlorophyll: green pigment in leaves that absorbs sunlight
  • Stomata: tiny pores in leaves through which CO₂ enters and O₂ exits
  • Parasitic plants: grow on other plants and absorb nutrients. Example: Cuscuta (Amarbel)
  • Insectivorous plants: trap and digest insects. Example: Venus Flytrap, Pitcher plant
  • Saprotrophic nutrition: organisms feed on dead organic matter. Example: fungi, bacteria
✅ Digest Answers
Q. What is photosynthesis? Write the equation.
Photosynthesis is the process by which green plants make food using sunlight, water and CO₂. Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. It takes place in chloroplasts in the presence of chlorophyll and sunlight.
Q. What are insectivorous plants? Give two examples.
Plants that trap and digest insects to fulfill their nitrogen requirement are insectivorous plants. They grow in nitrogen-poor soil. Examples: Venus Flytrap (closes leaves to trap insects), Pitcher plant (traps insects in pitcher-shaped leaves).
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Science

Chapter 4 — Heat

📌 Key Points
  • Temperature: measure of hotness or coldness. Unit: degree Celsius (°C)
  • Heat: form of energy that flows from hot to cold body. Unit: Joule (J) or calorie
  • Thermometer: instrument to measure temperature
  • Clinical thermometer: range 35°C to 42°C. Used for body temperature
  • Normal body temperature = 37°C (98.6°F)
  • Conduction: transfer of heat through direct contact. Occurs mainly in solids
  • Convection: transfer of heat through movement of fluids (liquids and gases)
  • Radiation: transfer of heat without any medium. Example: heat from sun
  • Dark, rough surfaces are good absorbers and radiators of heat
  • Light, shiny surfaces are poor absorbers (good reflectors)
✅ Digest Answers
Q. What is the difference between heat and temperature?
Heat is a form of energy that flows from a hot body to a cold body. It is measured in Joules. Temperature is a measure of hotness or coldness of an object measured in degrees Celsius. A large body at low temperature can have more heat than a small body at high temperature.
Q. Why do we wear white or light-coloured clothes in summer?
Light-coloured clothes absorb less heat and reflect more sunlight compared to dark-coloured clothes. So we feel cooler in white or light clothes during hot summer days.
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Science

Chapter 14 — Electric Current and Its Effects

📌 Key Points
  • Electric circuit: closed path through which current flows
  • Cell: source of electric energy. Battery = two or more cells connected
  • Switch: device to open or close a circuit
  • Conductor: material that allows current to flow. Example: copper, iron
  • Insulator: material that does not allow current to flow. Example: rubber, plastic
  • Heating effect of current: current produces heat in a conductor (used in bulb, heater, iron)
  • Fuse: safety device — melts and breaks circuit if too much current flows
  • Magnetic effect of current: current-carrying wire behaves like a magnet
  • Electromagnet: temporary magnet made by passing current through a coil around iron core
  • Electric bell: works on magnetic effect of current
✅ Digest Answers
Q. What is an electromagnet? Give its two uses.
An electromagnet is a temporary magnet formed by passing electric current through a coil wound around an iron core. It acts as a magnet only when current flows. Uses: 1) Electric bell 2) Cranes to lift heavy iron objects 3) Electric motors 4) Speakers.
Q. Why is a fuse used in electric circuits?
A fuse is a safety device made of low melting point wire. When excess current flows, the fuse wire melts and breaks the circuit, preventing damage to appliances and fire. It protects the circuit from short circuits and overloading.
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English Grammar

Nouns and Pronouns

📌 Key Points
  • Common noun: name of any person, place or thing. Example: boy, city, book
  • Proper noun: specific name. Example: Shashikant, Mumbai, Ganga. Always capitalised.
  • Collective noun: name of a group. Example: flock (birds), herd (cattle), team, class
  • Abstract noun: name of quality, feeling or idea. Example: honesty, happiness, knowledge
  • Countable noun: can be counted — book/books, child/children
  • Uncountable noun: cannot be counted — water, sugar, air
  • Personal pronouns: I, we, you, he, she, it, they
  • Possessive pronouns: mine, ours, yours, his, hers, theirs
  • Reflexive pronouns: myself, yourself, himself, herself, themselves
✅ Digest Answers
Q. What is an abstract noun? Give 4 examples.
An abstract noun is the name of a quality, feeling, state or idea that cannot be seen or touched. Examples: Courage, Kindness, Love, Freedom, Intelligence, Happiness.
Q. Identify nouns: "The team of students won the competition."
team (collective noun), students (common noun), competition (common noun)
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English Grammar

Adjectives and Degrees of Comparison

📌 Key Points
  • Positive degree: describes quality without comparison. Example: tall, fast, good
  • Comparative degree: comparison of two things. Add -er or use 'more'. Example: taller, faster, better
  • Superlative degree: highest degree. Add -est or use 'most'. Example: tallest, fastest, best
  • Short adjectives (1 syllable): add -er/-est. Example: big → bigger → biggest
  • Long adjectives: use more/most. Example: beautiful → more beautiful → most beautiful
  • Irregular adjectives: good→better→best, bad→worse→worst, much→more→most
  • Adjective of quality: beautiful, tall, honest
  • Adjective of quantity: some, much, little, enough
  • Adjective of number: one, five, first, many, few
✅ Digest Answers
Q. Give comparative and superlative of: beautiful, good, little
beautiful → more beautiful → most beautiful
good → better → best
little → less → least
Q. Change to superlative: "Riya is taller than all other girls."
Riya is the tallest girl.
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History

Tracing Changes Through a Thousand Years

📌 Key Points
  • Historians use manuscripts, inscriptions, coins, buildings to study the past
  • Manuscript: handwritten text, usually on paper, palm leaf or bark
  • Archives: places where manuscripts and records are kept
  • Maps in the medieval period were often not accurate — they showed the world differently
  • Al-Idrisi: Arab cartographer who made a map in 1154 — showed south at top
  • The word "Hindustan" was first used by Minhaj-i-Siraj to mean the subcontinent
  • Medieval period: roughly from 700 CE to 1750 CE
  • Languages change over time — scholars who copied manuscripts sometimes changed words
  • Jatis (castes) and religious groups were important social divisions
✅ Digest Answers
Q. What are manuscripts? Why are they important?
Manuscripts are handwritten texts, usually on paper, palm leaf or birch bark. They are important because they contain information about history, literature, religion and science of the past. They help historians understand how people lived centuries ago.
Q. Why is it difficult to study the medieval period?
Because: 1) Manuscripts were copied by hand and errors were introduced. 2) Words changed meaning over time. 3) Maps were not accurate. 4) Many sources are in different languages. 5) Records were not kept systematically.
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Geography

Our Environment — Key Topics

📌 Key Points
  • Environment: everything around us — living and non-living
  • Biotic components: all living things — plants, animals, humans, microorganisms
  • Abiotic components: non-living things — air, water, soil, sunlight
  • Ecosystem: interaction between biotic and abiotic components in an area
  • Lithosphere: solid crust of earth (land). Hydrosphere: water bodies. Atmosphere: layer of gases. Biosphere: zone of life
  • Natural environment: land, water, air, plants, animals
  • Human-made environment: buildings, roads, bridges
  • Rotation of Earth → day and night. Revolution → seasons
  • Earth takes 24 hours to complete one rotation, 365¼ days to complete one revolution
✅ Digest Answers
Q. What is an ecosystem?
An ecosystem is a system formed by the interaction of all living organisms (biotic components — plants, animals, bacteria) with the non-living physical environment (abiotic components — sunlight, water, soil, air) in a specific area. Example: forest ecosystem, pond ecosystem.
Q. Difference between rotation and revolution of Earth?
Rotation: Earth spinning on its own axis — takes 24 hours — causes day and night. Revolution: Earth moving around the Sun — takes 365¼ days (1 year) — causes seasons and years.

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