General Science Questions for SSC CHSL

Biology — Human Body and Diseases

This is the highest-frequency science area in SSC CHSL. Questions focus on organs and their functions, vitamins and minerals, diseases caused by deficiency or pathogens, and blood groups. You do not need deep medical knowledge — just the right associations. For example, which vitamin prevents which disease, which organ produces which enzyme or hormone.

• Vitamin A — Night blindness. Vitamin B12 — Anaemia. Vitamin C — Scurvy. Vitamin D — Rickets. Vitamin K — Blood clotting.
• Insulin is produced by the Pancreas (Beta cells). Deficiency causes Diabetes mellitus.
• Malaria — Plasmodium parasite, spread by Female Anopheles mosquito.
• Dengue and Chikungunya — Aedes mosquito (day-biting).
• Blood groups: A, B, AB (Universal Recipient), O (Universal Donor). Rh factor — positive or negative.
• Largest organ: Skin. Largest internal organ: Liver. Smallest bone: Stapes (ear). Longest bone: Femur (thigh).

Biology — Cell, Genetics, and Plant Science

Questions on cell biology focus on organelles and their jobs. Genetics questions usually test Mendel's laws or basic DNA facts. Plant science questions cover photosynthesis, plant hormones, and reproduction. These appear less frequently than human body but still come up.

• Mitochondria = Powerhouse of the cell (produces ATP via respiration).
• Chloroplast = site of Photosynthesis. Contains chlorophyll.
• DNA carries genetic information. Double helix model — Watson and Crick (1953).
• Photosynthesis equation: 6CO2 + 6H2O + light energy = C6H12O6 + 6O2.
• Auxin hormone promotes plant growth. Ethylene ripens fruits. Cytokinin promotes cell division.
• Mendel's Law of Segregation — two alleles separate during gamete formation.

Physics — Light, Sound, and Motion

SSC CHSL tests Physics at a very basic level — definitions, units, and everyday applications. Motion questions rarely need calculation; they test concepts like Newton's laws. Light and sound questions test properties such as reflection, refraction, and speed. Memorize units and inventors — these are easy one-liners.

• Speed of light in vacuum: 3 x 10^8 m/s. Speed of sound in air at 20 degrees C: 343 m/s. Sound cannot travel in vacuum.
• Newton's First Law: Inertia. Second Law: F = ma (force equals mass times acceleration). Third Law: Every action has equal and opposite reaction.
• Concave mirror — used in torches, headlights (converging). Convex mirror — used in rear-view mirrors (wider field of view).
• Myopia (short-sightedness) — corrected by Concave lens. Hypermetropia (long-sightedness) — corrected by Convex lens.
• Pitch of sound depends on frequency. Loudness depends on amplitude.
• Unit of force: Newton. Unit of pressure: Pascal. Unit of power: Watt. Unit of energy: Joule.

Physics — Electricity and Magnetism

Electricity questions are straightforward — Ohm's law, types of circuits, and common inventions. Magnetism questions ask about properties of magnets and Earth's magnetic field. Inventions and inventors are very commonly asked.

• In series circuit — current is same, voltage divides. In parallel circuit — voltage is same, current divides.
• Electric fuse protects against excess current (short circuit). It melts and breaks the circuit.
• SI unit of electric charge: Coulomb. Unit of current: Ampere. Unit of resistance: Ohm.
• Electromagnet loses magnetism when current is switched off. Permanent magnet keeps its property.
• Transformer works on AC (Alternating Current), not DC. It changes voltage levels.
• Fleming's Left Hand Rule: for direction of force on a current-carrying conductor in a magnetic field.

Chemistry — Elements, Compounds, and Everyday Chemistry

Chemistry questions in SSC CHSL are extremely fact-based. They test chemical names of common substances, pH values, acids and bases in daily life, and periodic table basics. You will almost never be asked to balance equations — just recognize substances and their properties.

• pH below 7 = Acidic. pH above 7 = Basic/Alkaline. pH 7 = Neutral. Pure water has pH 7.
• Common acids: Vinegar = Acetic acid. Lemon = Citric acid. Stomach acid = Hydrochloric acid. Ant sting = Formic acid.
• Common bases: Baking soda = Sodium bicarbonate (NaHCO3). Washing soda = Sodium carbonate. Bleaching powder = Calcium hypochlorite.
• Gold is 24 carat when pure. 22 carat gold = 22 parts gold + 2 parts other metals.
• Rust is Iron Oxide (Fe2O3). Rusting requires both water and oxygen.
• Laughing gas = Nitrous oxide (N2O). Dry ice = Solid CO2. Heavy water = D2O (Deuterium oxide).

Chemistry — Periodic Table and Important Discoveries

Aspirants often skip periodic table basics — but SSC CHSL frequently asks about the most reactive elements, noble gases, and properties of common metals. Also know important scientific discoveries and their inventors as one-liners.

• Noble gases (Group 18): Helium, Neon, Argon, Krypton, Xenon, Radon. They are inert — do not react.
• Most electronegative element: Fluorine. Most reactive metal: Cesium (or Potassium in simpler context).
• Mendeleev arranged elements by atomic mass. Modern periodic table (Moseley) uses atomic number.
• Radioactivity discovered by Henri Becquerel. Marie Curie discovered Radium and Polonium.
• Penicillin discovered by Alexander Fleming (1928). X-rays discovered by Wilhelm Roentgen.
• Nucleus of atom discovered by Ernest Rutherford. Neutron discovered by James Chadwick.

• Confusing Concave and Convex lenses with Concave and Convex mirrors — they have opposite uses. Mirror for headlights is Concave; mirror for rear-view is Convex. Lens for Myopia is Concave; lens for Hypermetropia is Convex.
• Mixing up Universal Donor (Blood group O) with Universal Recipient (Blood group AB). Remember: O = Opens to all (donor). AB = Accepts all (recipient).
• Confusing Aedes mosquito (Dengue, Chikungunya, Zika) with Anopheles mosquito (Malaria). Remember: A for Aedes, A for Ache (dengue gives severe joint pain).
• Writing Vitamin D for Night Blindness — it is actually Vitamin A. Vitamin D is for Rickets (weak bones). Use ABCDK: A=eyes, B=blood, C=scurvy, D=bones, K=clotting.
• Forgetting that Baking Soda and Washing Soda are different. Baking Soda = NaHCO3 (one H and one Na). Washing Soda = Na2CO3 (two Na). Washing is heavier — more sodium.

• Vitamin trick — ABCDK: A=Blindness, B12=Blood Anaemia, C=Scurvy, D=weak bones (Rickets), K=Klotting (Clotting). Say it as a word: AB-C-DK.
• For mosquitoes: Female Anopheles = Malaria = think AN-AN (Anopheles-Anaemia-like disease). Aedes = Dengue = A for Acute fever and day-time biting.
• Physics units chant: Force-Newton, Power-Watt, Energy-Joule, Pressure-Pascal, Charge-Coulomb, Resistance-Ohm. Say it daily like a mantra.
• pH scale memory: below 7 = Acidic (lemon, vinegar — things that taste sour and sharp). Above 7 = Basic (soap, baking soda — things that feel slippery). Neutral = water at 7.

• SSC CHSL typically asks 4 to 6 science questions in the GK section. Biology gets the most questions (2 to 3), followed by Chemistry (1 to 2), then Physics (1 to 2). Prioritize Biology first.
• Questions are almost always direct recall — no calculations needed. A question like 'Which vitamin prevents scurvy?' or 'What is the chemical name of baking soda?' is the standard format.
• Inventions and inventors are a recurring pattern. Keep a list of at least 10 famous discoveries with the scientist's name. Examples: Penicillin-Fleming, X-ray-Roentgen, Telephone-Graham Bell, Dynamite-Nobel.
• Do not expect tricky or twisted science questions — SSC CHSL is a 12th-pass exam. The facts are standard NCERT Class 8 to 10 level. If you have revised those textbooks once, you are well prepared.
• In the last week before the exam, revise science as a one-page fact sheet — just the key associations. Do not try to read new topics. Revision of known facts scores more than attempting unknown areas.