General Science — SSC GD Study Notes

Overview

General Science forms a critical pillar of the GK section in SSC GD, typically contributing 15–20 questions from Physics, Chemistry and Biology combined. This topic tests fundamental concepts at the matriculation level — the kind of science you encounter in daily life and read about in newspapers. Success here doesn't require deep theoretical knowledge but demands clarity on basic principles, definitions and real-world applications.

Questions are direct and factual: "Which vitamin deficiency causes scurvy?", "What is the SI unit of force?", or "Which gas is released during photosynthesis?" The exam rarely asks derivations or calculations but frequently tests your ability to connect concepts to everyday phenomena — why iron rusts, how vaccines work, or what causes tides. Students who revise NCERT Class 6–10 science textbooks thoroughly and stay updated on science-related current affairs (ISRO missions, Nobel prizes in science, new discoveries) score consistently well in this section.

Master the must-know lists: vitamins and diseases, SI units, common acids and bases, parts of the cell, endocrine glands and their hormones. These appear in every exam cycle with minor variations.

Key Concepts

• **Physics is about motion, energy and forces**: Understand the behaviour of objects (Newton's laws), energy transformations (potential to kinetic), properties of light (reflection, refraction) and electricity basics (current, resistance, conductors vs insulators).

• **Chemistry deals with matter and its transformations**: Focus on atomic structure (protons, neutrons, electrons), the periodic table layout, chemical reactions (synthesis, decomposition), and properties of common substances like acids (pH < 7, turn litmus red), bases (pH > 7, slippery feel) and salts.

• **Biology covers living systems**: The cell is the basic unit of life. Know major organelles (nucleus holds DNA, mitochondria produce energy, chloroplasts do photosynthesis in plants). Human body systems — digestive, respiratory, circulatory, nervous — and their main organs appear frequently.

• **Nutrition and deficiency diseases**: Vitamins (A, B-complex, C, D, E, K) and minerals (iron, calcium, iodine) each have specific roles and deficiency symptoms. For example, Vitamin C deficiency causes scurvy, iodine deficiency causes goitre.

• **Everyday applications connect theory to life**: Rusting is oxidation of iron, a mirror uses reflection, a lens in spectacles uses refraction, vaccines use weakened pathogens to build immunity, and pasteurisation kills bacteria in milk by heating.

• **Measurement matters**: SI units are standard — metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount of substance), candela (luminous intensity). Know conversions: 1 km = 1000 m, 1 kg = 1000 g.

• **Energy cannot be created or destroyed, only converted**: This is the law of conservation of energy. Potential energy (stored) converts to kinetic energy (motion) when you drop a ball. Chemical energy in food converts to mechanical energy in muscles.

• **Diseases are caused by pathogens or deficiencies**: Bacteria cause tuberculosis and cholera, viruses cause polio and influenza, protozoa cause malaria, fungi cause ringworm. Non-infectious diseases include diabetes, hypertension and cancer.

Formulas / Key Facts

**Physics:**

• Speed = Distance / Time
• Force = Mass × Acceleration (Newton's second law)
• Work = Force × Distance (in direction of force)
• Power = Work / Time
• Pressure = Force / Area
• Density = Mass / Volume
• Kinetic Energy = ½ × Mass × (Velocity)²
• Potential Energy = Mass × Gravity × Height
• SI unit of force: Newton (N); energy/work: Joule (J); power: Watt (W); pressure: Pascal (Pa)

**Chemistry:**

• Atomic number = number of protons
• Mass number = protons + neutrons
• pH scale: 0–6 acidic, 7 neutral, 8–14 basic
• Common acids: HCl (hydrochloric), H₂SO₄ (sulphuric), HNO₃ (nitric), CH₃COOH (acetic/vinegar)
• Common bases: NaOH (sodium hydroxide/caustic soda), Ca(OH)₂ (calcium hydroxide/slaked lime)
• Rusting: 4Fe + 3O₂ → 2Fe₂O₃ (iron oxide)
• Photosynthesis: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂ (in chloroplasts)

**Biology:**

• Red blood cells (RBCs) carry oxygen; white blood cells (WBCs) fight infection
• Haemoglobin in RBCs binds oxygen
• The heart has four chambers: two atria, two ventricles
• Human body temperature: 37°C (98.6°F)
• Normal human pulse rate: 72 beats per minute (at rest)
• Largest gland: liver; smallest bone: stapes (in ear); largest bone: femur (thigh)
• Vitamins: A (eyes, night blindness), B₁ (beriberi), B₁₂ (anaemia), C (scurvy), D (rickets), K (blood clotting)

Worked Examples

**Example 1 (Physics):** A car travels 150 km in 3 hours. What is its average speed? **Solution:** Speed = Distance / Time = 150 km / 3 h = 50 km/h. **Answer:** 50 km/h.

**Example 2 (Chemistry):** Identify the acid or base: A solution turns red litmus blue and feels slippery to touch. **Solution:** Bases turn red litmus blue and have a slippery feel. Acids turn blue litmus red. **Answer:** The solution is a base.

**Example 3 (Biology):** Which deficiency disease is caused by lack of Vitamin D? **Solution:** Vitamin D is essential for calcium absorption and bone health. Its deficiency in children causes rickets (soft, weak bones) and in adults causes osteomalacia. **Answer:** Rickets (in children) or osteomalacia (in adults).

**Example 4 (Physics):** An object of mass 2 kg is lifted to a height of 5 m. Calculate its potential energy. (Take g = 10 m/s²) **Solution:** Potential Energy = Mass × Gravity × Height = 2 kg × 10 m/s² × 5 m = 100 J. **Answer:** 100 Joules.

Common Mistakes

• **Confusing speed and velocity:** Speed is scalar (magnitude only); velocity is vector (magnitude + direction). In SSC GD, "speed" usually means average speed = total distance / total time. Students often add speeds directly instead of using total distance and total time separately.

• **Mixing up acids and bases on the pH scale:** Remember pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic. A common error is thinking pH 8 is acidic. Also, strong acids have low pH (near 0), strong bases have high pH (near 14).

• **Thinking all diseases are caused by germs:** Many diseases result from nutritional deficiencies (scurvy, beriberi, anaemia) or genetic/lifestyle factors (diabetes, hypertension). Not every disease needs an antibiotic — antibiotics work only against bacteria, not viruses.

• **Confusing mass and weight:** Mass is the amount of matter (measured in kg, constant everywhere). Weight is the force due to gravity (measured in Newtons, varies with gravity). On the moon, your mass stays the same but your weight is about one-sixth of Earth's weight.

• **Forgetting that plants also respire:** Photosynthesis produces oxygen during the day, but plants respire (use oxygen, release CO₂) all the time, day and night. Students often think plants only release oxygen.

Quick Reference

• **Newton's laws:** (1) Object stays at rest/motion unless force acts; (2) F = ma; (3) Action and reaction are equal and opposite.
• **pH: Acids < 7 < Bases.** Neutral = 7 (pure water).
• **Photosynthesis:** Plants use CO₂ + H₂O + light → glucose + O₂. Occurs in chloroplasts.
• **Common deficiencies:** Vit A → night blindness; Vit C → scurvy; Vit D → rickets; Iron → anaemia; Iodine → goitre.
• **SI base units:** m (length), kg (mass), s (time), A (current), K (temperature), mol (substance), cd (light).
• **Energy conversion:** Potential ↔ Kinetic. Energy is conserved, never destroyed.
• **Cell parts:** Nucleus (control centre, DNA), mitochondria (powerhouse), chloroplast (photosynthesis in plants), cell membrane (boundary).
• **Blood groups:** A, B, AB (universal recipient), O (universal donor). Rh factor: positive or negative.