General Science — SSC CGL Study Notes

Overview

General Science forms a critical component of the General Awareness section in SSC CGL Tier 1, typically contributing 10–15 questions out of 25. This section tests fundamental concepts from Physics, Chemistry, and Biology at the Class 10 level. The questions are designed to assess your understanding of basic scientific principles, everyday applications, and factual knowledge rather than complex problem-solving.

Success in General Science requires clarity on core concepts across all three branches. Questions often relate to practical applications—why the sky is blue, how vaccines work, what causes rusting—making this section accessible through real-world connections. Unlike other GA topics that demand extensive memorization, General Science rewards conceptual understanding combined with selective fact retention. Students should focus on fundamental laws, common phenomena, human body systems, and everyday chemistry rather than attempting to memorize entire textbooks.

The distribution is roughly equal among Physics, Chemistry, and Biology, so balanced preparation across all three is essential. This section can be a scoring area for students with science backgrounds but remains manageable for arts/commerce students who focus on high-yield topics systematically.

Key Concepts

• **Physics focuses on basic laws and phenomena**: Newton's laws of motion, work-energy-power relationships, basic electricity concepts (current, voltage, resistance), properties of light (reflection, refraction, dispersion), and everyday applications like why objects float, how levers work, and electromagnetic induction principles.

• **Chemistry emphasizes substance properties and reactions**: Understand the periodic table organization (groups, periods, metals/non-metals), acid-base concepts including pH scale and neutralization, types of chemical reactions (combination, decomposition, displacement), and common substances like salts, metals, and organic compounds.

• **Biology centers on human body systems and life processes**: The digestive, circulatory, respiratory, excretory, and nervous systems; basic cell structure and function; photosynthesis and respiration; vitamins and deficiency diseases; blood groups and immunity; and common diseases with their causes.

• **Measurement and units appear regularly**: SI units for fundamental quantities (meter, kilogram, second, ampere, kelvin), derived units (newton, joule, watt, pascal), and unit conversions form the foundation for numerical understanding.

• **Scientific discoveries and inventions are testable facts**: Who discovered/invented what, Nobel Prize winners in science, major scientific milestones, and the scientists associated with fundamental laws and theories.

• **Everyday applications bridge theory and practice**: Questions often connect scientific principles to daily life—why pressure cookers cook faster, how soap cleans, why iron rusts, how vaccines prevent disease—making conceptual clarity more valuable than rote memorization.

Formulas / Key Facts

**Physics**

• Speed = Distance / Time; Velocity includes direction
• Force = Mass × Acceleration (Newton's Second Law)
• Work = Force × Displacement; measured in joules
• Power = Work / Time; measured in watts
• Kinetic Energy = ½mv²; Potential Energy = mgh
• Ohm's Law: V = IR (Voltage = Current × Resistance)
• Lens formula: 1/f = 1/v - 1/u (focal length, image, object distance)
• Density = Mass / Volume; measured in kg/m³ or g/cm³

**Chemistry**

• pH scale ranges 0–14: <7 acidic, 7 neutral, >7 basic
• Atomic number = number of protons; Mass number = protons + neutrons
• Valency: H=1, O=2, N=3, C=4, Na=1, Cl=1, Ca=2, Al=3
• Common acids: HCl (hydrochloric), H₂SO₄ (sulfuric), HNO₃ (nitric)
• Common bases: NaOH (sodium hydroxide), Ca(OH)₂ (calcium hydroxide)
• Rusting formula: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ (iron oxide)
• Metals conduct electricity and heat; non-metals generally do not

**Biology**

• DNA double helix structure; RNA single strand; both carry genetic information
• Human heart: 4 chambers (2 atria, 2 ventricles); pumps oxygenated and deoxygenated blood
• Normal human body temperature: 37°C (98.6°F)
• Human blood groups: A, B, AB, O with Rh positive/negative
• Photosynthesis: 6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂
• Human chromosome count: 23 pairs (46 total)
• Vitamins: A (eyesight), B (energy), C (scurvy prevention), D (bones), K (blood clotting)
• White blood cells fight infection; Red blood cells carry oxygen via hemoglobin

Worked Examples

**Example 1: Physics Application** Q: A 2 kg object is moving at 10 m/s. What is its kinetic energy?

Solution: Use KE = ½mv²

• Mass (m) = 2 kg
• Velocity (v) = 10 m/s
• KE = ½ × 2 × (10)² = ½ × 2 × 100 = 100 joules

Answer: 100 J

**Example 2: Chemistry Concept** Q: When blue litmus paper is dipped in lemon juice, what color does it turn and why?

Solution:

• Lemon juice contains citric acid, making it acidic
• Acids turn blue litmus paper red
• pH of lemon juice is approximately 2–3 (acidic range)

Answer: Red, because lemon juice is acidic

**Example 3: Biology Application** Q: Which vitamin deficiency causes night blindness, and what are good dietary sources?

Solution:

• Night blindness (difficulty seeing in dim light) is caused by Vitamin A deficiency
• Vitamin A is essential for rhodopsin formation in retinal cells
• Good sources: carrots, papaya, milk, eggs, fish liver oil, green leafy vegetables

Answer: Vitamin A deficiency; found in carrots, milk, and green vegetables

Common Mistakes

• **Confusing speed and velocity**: Speed is scalar (magnitude only); velocity is vector (includes direction). "50 km/h north" is velocity; "50 km/h" is speed. Exam questions test this distinction explicitly.

• **Mixing up acid-base indicators**: Litmus, phenolphthalein, and methyl orange show different color changes. Remember: blue litmus turns red in acid; phenolphthalein is colorless in acid but pink in base; methyl orange is red in acid, yellow in base.

• **Misidentifying disease types**: Bacterial (tuberculosis, cholera), viral (polio, AIDS, COVID-19), protozoan (malaria), fungal (ringworm) diseases are distinct. Antibiotics work only on bacterial infections, not viral ones—a frequently tested point.

• **Reversing SI unit prefixes**: Kilo = 10³, milli = 10⁻³, micro = 10⁻⁶, nano = 10⁻⁹. Students often confuse micro and milli or misapply them in conversions.

• **Confusing arteries and veins**: Arteries carry blood away from the heart (not always oxygenated—pulmonary artery carries deoxygenated blood); veins carry blood toward the heart. The oxygenation status doesn't define them.

Quick Reference

• **Newton's Three Laws**: Inertia; F=ma; Every action has equal opposite reaction
• **pH memory**: 0–6 acid, 7 neutral, 8–14 base; stomach pH ~2, blood pH ~7.4
• **Vaccination**: Introduces weakened pathogen to build immunity without causing disease
• **Photosynthesis location**: Occurs in chloroplasts; chlorophyll is the green pigment
• **Human organ systems**: 11 major systems including digestive, circulatory, respiratory, nervous
• **Ohm's Law triangle**: Cover what you want to find; V=IR, I=V/R, R=V/I
• **Deficiency diseases**: Vitamin A (night blindness), B1 (beriberi), C (scurvy), D (rickets), Iron (anemia), Iodine (goiter)