General Science — Study Notes for TNPSC Group II/IIA
Overview
The syllabus emphasizes scientific knowledge, scientific temper, and applications — meaning you must understand basic principles and their real-world relevance, not just memorize isolated facts.
This topic bridges Physics, Chemistry, Biology, and everyday science applications. TNPSC often tests conceptual clarity rather than complex calculations. Questions may relate to health, environment, technology, agriculture, or recent scientific developments. A student with a Class 10–12 science foundation and awareness of current scientific news will find this section scoring.
Focus areas include: units and measurements, basic laws of motion and energy, common chemical reactions and compounds, human body systems, diseases and nutrition, and environmental science. The key is to build interconnected understanding — for instance, linking photosynthesis (biology) to carbon cycle (environment) to greenhouse effect (climate).
Key Concepts
- Scientific Method: Observation → Hypothesis → Experimentation → Analysis → Conclusion. Science progresses through evidence-based, repeatable inquiry — not belief or authority.
- SI Units: Seven base units — metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), candela (luminous intensity). All scientific measurements derive from these.
- Laws of Motion (Newton): First law — inertia; Second law — F = ma (force equals mass times acceleration); Third law — every action has an equal and opposite reaction.
- Energy Conservation: Energy cannot be created or destroyed, only transformed. Example: electrical energy → light + heat in a bulb.
- Atomic Structure: Atom = nucleus (protons + neutrons) + electrons in shells. Atomic number = number of protons; Mass number = protons + neutrons.
- Cell Theory: All living organisms are made of cells; cell is the basic structural and functional unit; all cells arise from pre-existing cells.
- Homeostasis: The body maintains stable internal conditions (temperature, pH, glucose levels) through feedback mechanisms — critical for survival.
- Ecosystem Balance: Energy flows (sun → producers → consumers → decomposers); matter cycles (carbon, nitrogen, water cycles). Disruption causes environmental problems.
Formulas / Key Facts
Physics Essentials
- Speed = Distance ÷ Time
- Velocity = Displacement ÷ Time (includes direction)
- Acceleration = Change in velocity ÷ Time
- Force = Mass × Acceleration (F = ma)
- Work = Force × Displacement (W = F × d)
- Power = Work ÷ Time
- Kinetic Energy = ½ × mass × velocity² (KE = ½mv²)
- Potential Energy = mass × gravity × height (PE = mgh)
- Ohm's Law: V = IR (Voltage = Current × Resistance)
- Speed of light in vacuum: 3 × 10⁸ m/s
- Speed of sound in air (at 20°C): approximately 343 m/s
Chemistry Essentials
- Water formula: H₂O; Common salt: NaCl; Baking soda: NaHCO₃
- pH scale: 0–14; pH < 7 = acidic; pH = 7 = neutral; pH > 7 = basic
- Photosynthesis equation: 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂
- Respiration equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
- Rusting: Iron + Oxygen + Moisture → Iron oxide (Fe₂O₃·xH₂O)
Biology Essentials
- Human body temperature: 37°C (98.6°F)
- Normal blood pressure: 120/80 mmHg
- Human chromosome count: 46 (23 pairs)
- Blood groups: A, B, AB, O (Rh factor: positive/negative)
- Universal donor: O negative; Universal recipient: AB positive
Worked Examples
Example 1: Unit Conversion Question: Convert 72 km/h to m/s.
Solution:
- 1 km = 1000 m; 1 hour = 3600 seconds
- 72 km/h = 72 × (1000/3600) m/s
- = 72 × (5/18) m/s
- = 20 m/s
Example 2: pH Identification Question: Lemon juice has pH around 2. Soap solution has pH around 10. Classify them.
Solution:
- pH 2 < 7 → Lemon juice is acidic
- pH 10 > 7 → Soap solution is basic/alkaline
Example 3: Energy Transformation Question: In a hydroelectric power plant, what energy conversions occur?
Solution:
- Water stored at height has potential energy
- Falling water gains kinetic energy
- Turbine converts kinetic energy to mechanical energy
- Generator converts mechanical energy to electrical energy
- Chain: Potential → Kinetic → Mechanical → Electrical
Common Mistakes
- Confusing speed with velocity: Speed is scalar (only magnitude); velocity is vector (magnitude + direction). "60 km/h north" is velocity, not just speed.
- Mixing atomic number and mass number: Atomic number = protons only (defines element); mass number = protons + neutrons. Carbon-12 has 6 protons, 6 neutrons.
- Assuming all acids are dangerous: Many acids are essential — HCl in stomach aids digestion; citric acid in fruits is harmless. Concentration and type matter.
- Thinking veins always carry deoxygenated blood: Pulmonary veins carry oxygenated blood from lungs to heart — the exception to remember.
- Believing sound travels faster than light: Light travels much faster (3 × 10⁸ m/s) than sound (343 m/s). That's why we see lightning before hearing thunder.
- Confusing conductors and insulators by material alone: Pure water is a poor conductor; impure/salt water conducts electricity well due to dissolved ions.
Quick Reference
- Scientific temper = questioning attitude + evidence-based thinking + rejecting superstition.
- Gravity on Earth ≈ 9.8 m/s² (often rounded to 10 m/s² in calculations).
- Density of water = 1 g/cm³ or 1000 kg/m³ — reference for floating/sinking.
- Vitamin deficiency diseases: A = Night blindness; B₁ = Beriberi; C = Scurvy; D = Rickets.
- Communicable vs Non-communicable: Communicable = spread person-to-person (TB, COVID); Non-communicable = lifestyle/genetic (diabetes, cancer).
- Ozone layer absorbs harmful UV radiation; found in stratosphere (15–35 km altitude).