20 Science GK Questions with Answers

1. In Döbereiner’s triad Li, Na, K, the atomic weight of Na is nearly equal to —
   1. the sum of Li and K
   2. the average of Li and K
   3. half of K
   4. three times Li
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   Answer: (B) the average of Li and K

   (7 + 39)/2 = 23 — the middle one’s atomic weight equals the average of the first and third.

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2. What is on the strip of a safety-match box?
   1. White phosphorus
   2. Sulphur
   3. KClO₃
   4. Red phosphorus and powdered glass
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   Answer: (D) Red phosphorus and powdered glass

   The head of the stick has KClO₃ + Sb₂S₃; the box has red phosphorus.

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3. Who discovered penicillin?
   1. Waksman
   2. Alexander Fleming
   3. Ehrlich
   4. Domagk
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   Answer: (B) Alexander Fleming

   In 1928 from the Penicillium fungus; Waksman gave streptomycin, Domagk the sulpha drug.

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4. Who led the IGMDP?
   1. Vikram Sarabhai
   2. APJ Abdul Kalam
   3. Homi J Bhabha
   4. D S Kothari
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   Answer: (B) APJ Abdul Kalam

   Dr APJ Abdul Kalam was made DRDL director in 1983 and given charge of leading the Integrated Guided Missile Development Programme (IGMDP).

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5. Why was TDSAT established?
   1. to license new telecom companies
   2. to take over telecom dispute resolution, separating it from TRAI
   3. to install mobile towers
   4. to fix internet speeds
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   Answer: (B) to take over telecom dispute resolution, separating it from TRAI

   TDSAT was created through an ordinance effective 29 May 2000, to carve dispute resolution out of TRAI and hand it to a separate tribunal.

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6. What is the chromosome count like in cells produced by meiosis?
   1. Same as the mother cell
   2. Half (haploid)
   3. Double
   4. Zero
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   Answer: (B) Half (haploid)

   Cells produced by meiosis are haploid (n), while the mother cell was diploid (2n).

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7. Which gland is called the "master gland"?
   1. Thyroid
   2. Pituitary gland
   3. Pancreas
   4. Adrenal gland
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   Answer: (B) Pituitary gland

   The pituitary gland controls several other glands, which is exactly why it is called the "master gland".

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8. In nitrification, what does ammonia turn into?
   1. Nitrogen gas
   2. Nitrite-nitrate
   3. Ammonium ion
   4. Urea
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   Answer: (B) Nitrite-nitrate

   Nitrifying bacteria (like Nitrosomonas) convert ammonia into nitrite and then nitrate.

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9. Why is thermal pollution harmful to aquatic life?
   1. The water turns salty
   2. The water freezes
   3. Hot water holds less oxygen
   4. Light is reduced
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   Answer: (C) Hot water holds less oxygen

   The solubility of gases falls as temperature rises, while fish need more oxygen.

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10. What vehicle carries the Nag missile's land version?
    1. the Arjun tank
    2. NAMICA
    3. T-90 Bhishma
    4. BMP-2
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    Answer: (B) NAMICA

    The Nag missile's land version is carried by a tracked vehicle called NAMICA (Nag Missile Carrier).

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11. Which of these is a chemical change?
    1. Melting of ice
    2. Milk turning into curd
    3. Sublimation of camphor
    4. Dissolving salt
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    Answer: (B) Milk turning into curd

    Curd contains a new substance (lactic acid) and the change does not reverse — the other three are physical changes.

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12. Oxidation state of iron in K₄[Fe(CN)₆]?
    1. +3
    2. 0
    3. +2
    4. +6
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    Answer: (C) +2

    4(+1) + x + 6(−1) = 0 → x = +2; +3 in K₃[Fe(CN)₆].

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13. In which layer of the atmosphere is the ozone layer?
    1. Troposphere
    2. Stratosphere
    3. Mesosphere
    4. Thermosphere
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    Answer: (B) Stratosphere

    The ozone layer is at ≈ 15–35 km in the stratosphere; that is why temperature rises with height there.

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14. Which of these levers always has a mechanical advantage less than 1?
    1. scissors
    2. tongs
    3. wheelbarrow
    4. see-saw
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    Answer: (B) tongs

    Tongs are a third-class lever (effort in the middle), whose effort arm is always shorter than the load arm.

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15. In which medium does light travel fastest?
    1. water
    2. vacuum
    3. glass
    4. diamond
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    Answer: (B) vacuum

    The speed of light is highest in vacuum (3 × 10⁸ m/s); the higher the refractive index, the lower the speed.

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16. Through what medium does the TV signal reach the home in a DTH service?
    1. through a ground cable
    2. directly from a satellite to a dish antenna
    3. through a mobile tower
    4. through a telephone line
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    Answer: (B) directly from a satellite to a dish antenna

    In DTH (Direct-To-Home), the signal travels straight from a satellite to the home's dish antenna and set-top box.

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17. What kind of photoperiod plant is Xanthium?
    1. Long-day
    2. Short-day
    3. Day-neutral
    4. Vernalisation-dependent
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    Answer: (B) Short-day

    Xanthium is a short-day plant (SDP), needing light below a fixed critical duration to flower.

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18. What is Dolly the sheep known for?
    1. being the first GM organism
    2. being the first mammal cloned from an adult cell
    3. being the first transgenic plant
    4. none of these
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    Answer: (B) being the first mammal cloned from an adult cell

    Dolly the sheep was the first mammal successfully cloned from an adult cell through differentiation.

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19. As temperature rises, the solubility of gases in water —
    1. increases
    2. decreases
    3. stays the same
    4. first rises then falls
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    Answer: (B) decreases

    Dissolving a gas is exothermic; on heating the gas escapes — ponds lose oxygen in summer.

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20. Why is nitrogen filled in chips packets?
    1. For taste
    2. To add moisture
    3. To add weight
    4. To stop rancidity (oxidation)
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    Answer: (D) To stop rancidity (oxidation)

    N₂ is inert; with no oxygen the fat is not oxidised (no staleness).

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