General Science in SSC CGL is not a single chapter — it is a three-subject blend of Physics, Chemistry, and Biology, tested at the level of what a sharp Class 10–12 student should know without opening a textbook. The questions look simple on paper but catch you when your recall is slightly fuzzy: you know hydrogen bonding is "strong," but do you know it's stronger than dipole-dipole? You know ionic bonds involve electron transfer, but do you know the electronegativity difference threshold?
Think of General Science as three overlapping circles on a Venn diagram:
The analogy that works best here: General Science questions are like multiple-choice trivia at a quiz competition. The answer is almost always in the question itself if you know your definitions cold. The trap is the "nearly right" option — London dispersion forces versus van der Waals forces, guttation versus transpiration, DNA polymerase versus DNA helicase. These are precision questions. One crisp sentence of definition separates a correct answer from a wrong one.
At the SSC CGL level, you will not be asked to derive equations or solve numerical problems in General Science. You will be asked to identify, classify, and compare. So your preparation strategy is definitional accuracy plus the ability to rank concepts (which is stronger, which comes first, which direction does a trend move).
Light behaves as both a wave and a particle. For SSC CGL, you need the wave behavior sorted first.
n₁ sin θ₁ = n₂ sin θ₂.The photon is the carrier particle of the electromagnetic force. It has no mass, travels at c = 3 × 10⁸ m/s, and mediates all electromagnetic interactions from radio waves to gamma rays.
Chemical bonds are forces holding atoms together within a molecule. Intermolecular forces hold molecules together (weaker than bonds).
Bond types by electronegativity difference:
> 1.7 → Ionic bond: electrons are fully transferred. One atom becomes a cation (+), the other an anion (−). Example: NaCl.0.4–1.7 → Polar covalent bond: electrons are shared unequally.< 0.4 → Non-polar covalent bond: electrons are shared equally.Intermolecular forces in increasing strength:
London dispersion < Van der Waals (dipole-induced dipole) < Dipole-dipole < Hydrogen bonding
Hydrogen bonding occurs when H is bonded to a highly electronegative atom — N, O, or F only. The partial positive charge on H attracts a lone pair on another electronegative atom. This is why water has an unusually high boiling point for its molecular weight.
Periodic table trends:
DNA (Deoxyribonucleic acid) is the molecule that stores genetic information in most organisms (viruses can use RNA instead). It is a double helix made of nucleotides, each containing a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C). Base pairing: A–T and G–C.
DNA replication is semi-conservative — each strand acts as a template for a new strand. The key enzymes:
| Enzyme | Role | |---|---| | DNA helicase | Unwinds the double helix by breaking hydrogen bonds between base pairs | | DNA primase | Synthesizes the RNA primer to start replication | | DNA polymerase | Adds new nucleotides to build the new strand | | DNA ligase | Joins Okazaki fragments on the lagging strand |
The exam question is almost always "which enzyme unwinds the helix" — that is helicase, not polymerase. Polymerase builds, helicase unwinds.
Plant water processes:
The confusion trap: transpiration vs. guttation. Transpiration = vapor through stomata (daytime, active). Guttation = liquid drops through hydathodes (night, passive).
Hydrogen bonding only occurs when H is attached to Nitrogen, Oxygen, or Fluorine — remember "NOF" (sounds like "knock off"). If a question asks which molecule has hydrogen bonding, check whether H is directly bonded to N, O, or F. H₂O: yes. HCl: no (Cl is not N, O, or F). NH₃: yes.
Standard confusion time when second-guessing: 30s. With the NOF check: 5s — one mental scan of the molecule.
DNA helicase is named after the helix it unwinds. Think of a helicopter rotor spinning to break apart the two strands of the helix. When the exam asks "which enzyme unwinds DNA," you are looking for the one whose name contains "helix" — helicase. Polymerase builds (think "polymer" = long chain), ligase links (think "ligament" = connects).
Without this anchor, test-takers take 20–25s second-guessing polymerase vs. helicase. With it: 5s.
Draw a periodic table mentally. Ionization energy and electronegativity both increase in the same two directions: left to right (→) across a period, and bottom to top (↑) in a group. Atomic radius does the opposite: increases right to left and top to bottom. One set of arrows covers three properties. If a question gives you two elements and asks which has higher ionization energy, locate them mentally — whoever is higher and more to the right wins.
Eliminates the need to recall separate rules for each trend: reduces 3 memorization items to 1 arrow pair.
Transpiration = Daytime, sToMata, vapor. Guttation = niGht, hydathodes, liquid drops. The capital letters give you: T = daytime Stomata vapor; G = niGht liquid. If the question says "water vapor through stomata," it is transpiration. If it says "water drops at leaf tips at night," it is guttation. This binary split eliminates the two most common wrong answers in under 5 seconds versus 15–20 seconds of uncertain recall.
Electronegativity difference greater than 1.7 → ionic bond. Less than 1.7 → covalent (polar or non-polar). This number appears directly in MCQ options sometimes as "large difference = ionic." NaCl: Na is 0.93, Cl is 3.16, difference = 2.23 → ionic. HCl: H is 2.20, Cl is 3.16, difference = 0.96 → polar covalent. Knowing "1.7" as the single cutoff saves you from evaluating all four bond types every time. Step count: 4 steps (evaluate each bond type) → 1 step (check if difference is large).
When a General Science question appears, run this three-step decision tree:
Step 1 — Identify the domain. Is this Physics (particles, light, forces, motion, electricity), Chemistry (elements, bonds, reactions, periodic table), or Biology (cells, DNA, plants, human body)? This takes 2 seconds and activates the right memory cluster.
Step 2 — Apply the definition test. Most General Science questions reduce to one definitional sentence. State the definition of the key term in the question. Diffraction = bending around obstacles. Ionization energy = energy to remove an electron from a gaseous atom. Transpiration = vapor loss through stomata. If your definition matches one option cleanly, mark it.
Step 3 — Eliminate by "nearly right" trap. If two options look similar (helicase vs. polymerase, transpiration vs. guttation, hydrogen bonding vs. dipole-dipole), use your anchor rule (NOF, Day/Night, 1.7 threshold, Helicase/Helicopter) to break the tie in under 5 seconds. Do not sit and reason from scratch under time pressure — the anchor rules are precisely for this moment.
Target time per General Science MCQ: 25–35 seconds. If you cross 45 seconds, mark your best guess and move on. These are recall questions, not reasoning questions — extra time rarely changes the answer.
Why this question: Tests whether you know the hierarchy of intermolecular forces — a precision-ranking question where all four options are real forces, so elimination requires knowing the order.
Solving path: The question asks for the strongest intermolecular force from the list. Apply the hierarchy: London dispersion < Van der Waals < Dipole-dipole < Hydrogen bonding. Hydrogen bonding is at the top. Additionally, apply the NOF rule — hydrogen bonding requires H attached to N, O, or F, making it uniquely strong among intermolecular forces. Answer: Hydrogen bonding.
Why this question: Tests the ionic bond definition and the electronegativity difference rule — a foundational chemistry concept that appears in multiple forms.
Solving path: "Large difference in electronegativity" is the textbook trigger phrase for ionic bonds. When electronegativity difference exceeds approximately 1.7, electron transfer (not sharing) occurs, forming ions. Eliminate covalent (sharing, not transfer), metallic (electron sea in metals), and hydrogen bond (a type of intermolecular force, not an intramolecular bond). Answer: Ionic bond.
Why this question: Transpiration vs. guttation is the classic trap. The question includes guttation as option D to catch those who confuse the two processes.
Solving path: The question says "water vapor through leaves" — that's the vapor keyword. Transpiration = vapor through stomata. Guttation = liquid drops through hydathodes at night. Respiration releases CO₂ and water but is a cellular energy process, not primarily a water-release mechanism. Photosynthesis uses water, does not release it through leaves as vapor. Answer: Transpiration.
Why this question: Diffraction is frequently confused with refraction and dispersion. The phrase "bends around edges or through narrow openings" is the defining description.
Solving path: Refraction = bending at an interface between two media (change in speed). Reflection = bouncing back. Dispersion = splitting of white light into colors. Diffraction = bending around obstacles or through narrow openings when the obstacle/slit size is comparable to the wavelength. The phrase "around the edges" is the giveaway — that is diffraction's definition. Answer: Diffraction.
Why this question: Four enzymes in DNA replication are tested here. The question isolates "unwinding" as the function, which uniquely belongs to helicase.
Solving path: Use the Helicopter anchor — helicase unwinds (spins like a rotor). DNA polymerase adds nucleotides (builds the new strand). DNA ligase joins fragments (connects, like a ligament). DNA primase lays the RNA primer. The word "unwinding" in the question locks onto helicase. Answer: DNA helicase.
Confusing hydrogen bond as a type of chemical bond: Hydrogen bonding is an intermolecular force (between molecules), not a covalent or ionic bond (within a molecule). When a question asks about "chemical bonds," hydrogen bond is not in the list unless the question specifically says "intermolecular forces."
Choosing DNA polymerase for the unwinding step: Polymerase is the most famous DNA enzyme, so test-takers default to it. Polymerase synthesizes — it cannot proceed until helicase has already unwound the helix. Sequence matters: helicase first, then polymerase.
Saying all Van der Waals forces are London dispersion forces: London dispersion forces are a subset of Van der Waals forces. Van der Waals is the umbrella term covering London dispersion, dipole-induced dipole, and sometimes dipole-dipole interactions depending on the textbook. In the hierarchy question, Van der Waals (as a category) sits above London dispersion.
Mixing up transpiration and guttation trigger conditions: Guttation happens at night or early morning when stomata are closed and root pressure builds up. Transpiration is an active daytime process. If a question says "water drops observed on leaves in the morning," the answer is guttation, not transpiration.
Reversing ionization energy trend in a group: Ionization energy decreases as you go down a group (Lithium > Sodium > Potassium), not increases. The common error is applying the "left to right increases" rule without remembering that going down a group means electrons are farther from the nucleus and easier to remove.
Treating diffraction as the same as refraction: Refraction requires two different media (glass/water/air interface). Diffraction requires a single medium with an obstacle or slit. If the question mentions "edge of an obstacle" or "narrow slit," that is diffraction. If it mentions "passing from one medium to another," that is refraction.