UPSC Prelims · Bite-size lessons
General Science
About 7 min · General Studies Paper I · English
Time worked out from the lesson's 485 words at 150 words a minute, plus a minute for each question.
General Science in UPSC Prelims tests your basic understanding of physics, chemistry, and biology at the 10th-standard level, along with awareness of recent scientific and technological developments. Unlike specialised science papers, this section does not require deep subject expertise—it focuses on conceptual clarity and the ability to connect science with everyday life, government programmes, and current affairs.
Key ideas
- Newton's Laws of Motion govern all mechanical phenomena: inertia, F = ma, and action-reaction pairs explain everything from rocket propulsion to why passengers lurch forward when a bus brakes.
- Energy cannot be created or destroyed, only transformed (Law of Conservation of Energy). This underpins power generation, metabolic processes, and climate science.
- Acids donate H⁺ ions; bases donate OH⁻ ions. pH scale runs 0–14; below 7 is acidic, above 7 is basic. Human blood pH is slightly basic (7.35–7.45).
- Cell is the basic unit of life. Prokaryotes (bacteria) lack a nucleus; eukaryotes (plants, animals, fungi) have membrane-bound organelles.
- DNA carries genetic information in a double-helix structure. Genes code for proteins. Mutations cause genetic disorders and also drive evolution.
Watch out for
- Confusing nuclear fission and fusion → Fission splits heavy atoms (used in current reactors and bombs); fusion combines light atoms (powers the sun, not yet commercially viable on Earth).
- Believing antibiotics work on viruses → Antibiotics target bacteria only. Viral infections (flu, COVID-19) require antivirals or vaccines. Misuse leads to antimicrobial resistance.
- Mixing up conduction, convection, and radiation → Conduction: heat transfer through direct contact (metal spoon in hot soup). Convection: heat transfer through fluid movement (boiling water). Radiation: heat transfer without medium (sunlight reaching Earth).
Quick reference
- ISRO launch vehicles: PSLV (polar satellites, reliable workhorse), GSLV (heavier payloads, cryogenic engine), LVM3 (Chandrayaan-3, Gaganyaan)
- Vitamins: A, D, E, K are fat-soluble (stored in body); B-complex and C are water-soluble (excess excreted)
- Greenhouse gases (descending warming potential per molecule): SF₆ > HFCs > N₂O > CH₄ > CO₂
- Blood group compatibility: O-negative is universal donor; AB-positive is universal recipient
- India's thorium reserves are among world's largest—basis for third stage of nuclear programme
Check yourself: 3 questions
1. Which of the following statements about the human circulatory system is correct?
2. A person standing in front of a plane mirror notices that when he moves 2 metres away from the mirror, the distance between him and his image increases by how much?
3. Which among the following is the primary reason for the blue colour of the sky?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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