General Science — TNPSC Group IV Study Notes
Overview
General Science forms a significant portion of the TNPSC Group IV examination, testing candidates on fundamental scientific concepts at the SSLC (10th standard) level. This section covers Physics, Chemistry, Botany, and Zoology — essentially the core science you studied in school but now applied to competitive exam formats.
The exam doesn't require deep theoretical knowledge or complex derivations. Instead, it tests your ability to recall basic scientific facts, understand everyday phenomena through scientific principles, and apply fundamental concepts to practical situations. Questions often relate science to daily life — why the sky is blue, how vaccines work, what causes rust, or which vitamin deficiency causes night blindness.
Mastering this section requires systematic revision of SSLC science textbooks combined with awareness of scientific developments in current affairs.
Key Concepts
- Matter exists in three states — solid, liquid, and gas — with distinct properties of shape, volume, and compressibility. Plasma is the fourth state found in stars and fluorescent tubes.
- Newton's three laws of motion explain all mechanical phenomena: inertia (objects resist change), F = ma (force produces acceleration), and action-reaction pairs.
- Energy can neither be created nor destroyed, only transformed from one form to another — this Law of Conservation of Energy governs all physical and chemical processes.
- Atoms combine through ionic or covalent bonding — ionic involves electron transfer (NaCl), covalent involves electron sharing (H₂O).
- Photosynthesis is the foundation of life on Earth — plants convert CO₂ and water into glucose and oxygen using sunlight and chlorophyll.
- Human body systems work in coordination — circulatory (blood transport), respiratory (gas exchange), digestive (nutrient absorption), nervous (signal transmission), and excretory (waste removal).
- pH scale measures acidity and alkalinity — below 7 is acidic, exactly 7 is neutral, above 7 is basic. Human blood maintains pH around 7.4.
- Heredity operates through DNA — genes carry traits from parents to offspring, with dominant and recessive allele patterns determining expression.
Formulas / Key Facts
Physics Formulas:
- Speed = Distance ÷ Time
- Velocity = Displacement ÷ Time
- Acceleration = Change in velocity ÷ Time
- Force = Mass × Acceleration (F = ma)
- Work = Force × Distance (W = F × d)
- Power = Work ÷ Time
- Kinetic Energy = ½ × mass × velocity² (KE = ½mv²)
- Potential Energy = mass × gravity × height (PE = mgh)
- Ohm's Law: Voltage = Current × Resistance (V = IR)
- Density = Mass ÷ Volume
Chemistry Facts:
- Atomic number = number of protons = number of electrons (in neutral atom)
- Mass number = protons + neutrons
- Valency determines combining capacity of elements
- Acids release H⁺ ions; bases release OH⁻ ions
- Rusting: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃
Biology Facts:
- Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Normal human body temperature: 37°C or 98.6°F
- Normal blood pressure: 120/80 mmHg
- RBC lifespan: 120 days
- WBC function: immunity and defence
- Haemoglobin carries oxygen; contains iron
Worked Examples
Example 1: Force Calculation A car of mass 1000 kg accelerates at 2 m/s². Find the force applied.
Solution:
- Given: mass (m) = 1000 kg, acceleration (a) = 2 m/s²
- Formula: F = m × a
- F = 1000 × 2 = 2000 N
- Answer: 2000 Newtons
Example 2: Identifying Acid-Base Reaction What happens when hydrochloric acid reacts with sodium hydroxide?
Solution:
- HCl (acid) + NaOH (base) → NaCl + H₂O
- This is a neutralisation reaction
- Products: common salt (sodium chloride) and water
- The reaction is exothermic (releases heat)
Example 3: Deficiency Disease A person suffers from bleeding gums and slow wound healing. Which vitamin is deficient?
Solution:
- Bleeding gums and poor wound healing indicate Vitamin C deficiency
- Disease name: Scurvy
- Sources: Citrus fruits (orange, lemon), amla, guava, tomato
- Vitamin C is also called ascorbic acid
Common Mistakes
- Confusing speed with velocity → Speed is scalar (magnitude only), velocity is vector (magnitude + direction). A car going in circles has speed but zero average velocity.
- Mixing up atomic number and mass number → Atomic number is protons only (identifies the element); mass number is protons plus neutrons.
- Believing plants only respire at night → Plants respire 24 hours; photosynthesis occurs only in light. During day, photosynthesis rate exceeds respiration rate.
- Thinking arteries always carry oxygenated blood → Pulmonary artery carries deoxygenated blood from heart to lungs. Arteries are defined by direction (away from heart), not oxygen content.
- Confusing concave and convex mirrors/lenses → Concave mirror converges light (used in torches, headlights); convex mirror diverges light (used in vehicle rear-view mirrors). Remember: "cave" suggests hollow inward.
Quick Reference
- SI unit of force: Newton (N); SI unit of energy: Joule (J)
- Vitamin deficiencies: A = Night blindness; B₁ = Beriberi; C = Scurvy; D = Rickets; K = Bleeding disorders
- Blood groups: A, B, AB (universal recipient), O (universal donor)
- Largest organ: Skin; Largest gland: Liver; Largest cell: Ovum (egg cell)
- Good conductors: Metals (silver best); Insulators: Rubber, plastic, wood, glass
- Acids turn blue litmus red; bases turn red litmus blue