General science: 49 questions with answers

All science questions

Options are listed alphabetically. Open "Show answer" to see the answer, our explanation and the source we checked it against.

1. sci-001What is the pH of a neutral solution?

   1. 0
   2. 1
   3. 14
   4. 7
   Show answer

   Answer: 7

   NCERT explains that the pH of a neutral solution is 7. Values below 7 are acidic, and values rising from 7 to 14 show an increasing strength of alkali.

   Source: NCERT, Class X Science: Acids, Bases and Salts (PDF page 9). Checked 26 October 2026.

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2. sci-002Tooth decay starts when the pH of the mouth falls below which value?

   1. 3.0
   2. 5.5
   3. 6.8
   4. 7.5
   Show answer

   Answer: 5.5

   NCERT notes that tooth decay starts when mouth pH is lower than 5.5. Tooth enamel, made of calcium hydroxyapatite, is the hardest substance in the body.

   Source: NCERT, Class X Science: Acids, Bases and Salts (PDF page 11). Checked 26 October 2026.

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3. sci-003Plaster of Paris is obtained by heating which substance at 373 K?

   1. Baking soda
   2. Common salt
   3. Gypsum
   4. Limestone
   Show answer

   Answer: Gypsum

   NCERT says gypsum (CaSO₄·2H₂O) heated at 373 K loses water molecules and becomes calcium sulphate hemihydrate, known as Plaster of Paris.

   Source: NCERT, Class X Science: Acids, Bases and Salts (PDF page 16). Checked 26 October 2026.

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4. sci-004Milk of magnesia, used to relieve excess stomach acid, is which compound?

   1. Calcium carbonate
   2. Magnesium hydroxide
   3. Magnesium sulphate
   4. Sodium chloride
   Show answer

   Answer: Magnesium hydroxide

   NCERT describes antacids as bases that neutralise excess stomach acid, naming magnesium hydroxide (milk of magnesia), a mild base, as one example.

   Source: NCERT, Class X Science: Acids, Bases and Salts (PDF page 11). Checked 26 October 2026.

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5. sci-005The stinging hairs of nettle leaves inject which acid?

   1. Citric acid
   2. Lactic acid
   3. Methanoic acid
   4. Oxalic acid
   Show answer

   Answer: Methanoic acid

   NCERT says nettle's stinging hairs inject methanoic acid, causing a burning pain.

   Source: NCERT, Class X Science: Acids, Bases and Salts (PDF page 11). Checked 26 October 2026.

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6. sci-006Which two metals are the best conductors of heat, according to NCERT?

   1. Gold and zinc
   2. Iron and aluminium
   3. Lead and mercury
   4. Silver and copper
   Show answer

   Answer: Silver and copper

   NCERT states that silver and copper are the best conductors of heat, while lead and mercury are comparatively poor conductors.

   Source: NCERT, Class X Science: Metals and Non-metals (PDF page 2). Checked 26 October 2026.

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7. sci-007Which non-metal is a liquid at room temperature?

   1. Bromine
   2. Iodine
   3. Phosphorus
   4. Sulphur
   Show answer

   Answer: Bromine

   NCERT notes that non-metals are solids or gases, except bromine, which is a liquid.

   Source: NCERT, Class X Science: Metals and Non-metals (PDF page 3). Checked 26 October 2026.

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8. sci-008Which allotrope of carbon is the hardest natural substance known?

   1. Charcoal
   2. Coal
   3. Diamond
   4. Graphite
   Show answer

   Answer: Diamond

   NCERT describes diamond, an allotrope of carbon, as the hardest natural substance known, with very high melting and boiling points.

   Source: NCERT, Class X Science: Metals and Non-metals (PDF page 4). Checked 26 October 2026.

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9. sci-009Which two metals have melting points so low that they melt if kept on the palm?

   1. Gallium and caesium
   2. Mercury and lead
   3. Sodium and potassium
   4. Tin and zinc
   Show answer

   Answer: Gallium and caesium

   NCERT notes that most metals have high melting points but gallium and caesium have very low ones, low enough to melt on your palm.

   Source: NCERT, Class X Science: Metals and Non-metals (PDF page 4). Checked 26 October 2026.

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10. sci-010Galvanisation protects iron and steel from rusting by coating them with a thin layer of which metal?

    1. Chromium
    2. Copper
    3. Tin
    4. Zinc
    Show answer

    Answer: Zinc

    NCERT defines galvanisation as coating steel and iron with a thin layer of zinc. Other ways to prevent rusting include painting, oiling, chrome plating and making alloys.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 18). Checked 26 October 2026.

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11. sci-011What is an alloy called when one of its metals is mercury?

    1. A bronze
    2. A solder
    3. An amalgam
    4. An ore
    Show answer

    Answer: An amalgam

    NCERT states that if one of the metals in an alloy is mercury, the alloy is known as an amalgam.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 18). Checked 26 October 2026.

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12. sci-012Brass is an alloy of copper and which other metal?

    1. Lead
    2. Nickel
    3. Tin
    4. Zinc
    Show answer

    Answer: Zinc

    NCERT gives brass as an alloy of copper and zinc, and bronze as an alloy of copper and tin.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 18). Checked 26 October 2026.

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13. sci-013Bronze is an alloy of copper and which other metal?

    1. Aluminium
    2. Iron
    3. Tin
    4. Zinc
    Show answer

    Answer: Tin

    NCERT gives bronze as an alloy of copper and tin. Like brass, it conducts electricity less well than pure copper.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 18). Checked 26 October 2026.

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14. sci-014Aqua regia, which can dissolve gold, mixes concentrated hydrochloric acid and concentrated nitric acid in which ratio?

    1. 1 : 1
    2. 1 : 3
    3. 2 : 1
    4. 3 : 1
    Show answer

    Answer: 3 : 1

    NCERT describes aqua regia ("royal water") as a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3 : 1.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 8). Checked 26 October 2026.

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15. sci-015In 22 carat gold used for ornaments, 22 parts of pure gold are alloyed with how many parts of copper or silver?

    1. 1 part
    2. 2 parts
    3. 4 parts
    4. 8 parts
    Show answer

    Answer: 2 parts

    NCERT explains that pure (24 carat) gold is soft, so for jewellery 22 parts of pure gold are alloyed with 2 parts of copper or silver.

    Source: NCERT, Class X Science: Metals and Non-metals (PDF page 18). Checked 26 October 2026.

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16. sci-016Which protein-digesting enzyme is released by the gastric glands in the stomach wall?

    1. Amylase
    2. Lipase
    3. Pepsin
    4. Trypsin
    Show answer

    Answer: Pepsin

    NCERT says the gastric glands release hydrochloric acid, the protein-digesting enzyme pepsin, and mucus. The acid creates the medium pepsin needs.

    Source: NCERT, Class X Science: Life Processes (PDF page 7). Checked 26 October 2026.

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17. sci-017What is the respiratory pigment in human beings?

    1. Chlorophyll
    2. Haemoglobin
    3. Insulin
    4. Melanin
    Show answer

    Answer: Haemoglobin

    NCERT names haemoglobin as the human respiratory pigment. It has a very high affinity for oxygen and is present in red blood corpuscles.

    Source: NCERT, Class X Science: Life Processes (PDF page 12). Checked 26 October 2026.

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18. sci-018What are the filtration units of the kidney called?

    1. Alveoli
    2. Nephrons
    3. Neurons
    4. Villi
    Show answer

    Answer: Nephrons

    NCERT explains that each kidney has large numbers of filtration units called nephrons, packed close together.

    Source: NCERT, Class X Science: Life Processes (PDF page 19). Checked 26 October 2026.

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19. sci-019The finger-like projections that increase the surface area for absorption in the small intestine are called what?

    1. Alveoli
    2. Cilia
    3. Nephrons
    4. Villi
    Show answer

    Answer: Villi

    NCERT says the inner lining of the small intestine has numerous villi, richly supplied with blood vessels that carry absorbed food to the body.

    Source: NCERT, Class X Science: Life Processes (PDF page 8). Checked 26 October 2026.

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20. sci-020In plants, which tissue moves water and minerals obtained from the soil?

    1. Cambium
    2. Epidermis
    3. Phloem
    4. Xylem
    Show answer

    Answer: Xylem

    NCERT describes two conducting pathways: xylem moves water and minerals from the soil, and phloem transports products of photosynthesis from the leaves.

    Source: NCERT, Class X Science: Life Processes (PDF page 16). Checked 26 October 2026.

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21. sci-021What are the tiny pores on the surface of leaves, through which most gaseous exchange takes place, called?

    1. Chloroplasts
    2. Lenticels
    3. Root hairs
    4. Stomata
    Show answer

    Answer: Stomata

    NCERT describes stomata as tiny pores on the leaf surface through which massive amounts of gaseous exchange take place.

    Source: NCERT, Class X Science: Life Processes (PDF page 5). Checked 26 October 2026.

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22. sci-022Myopia (near-sightedness) is corrected using which kind of lens?

    1. A bifocal lens only
    2. A concave lens of suitable power
    3. A convex lens of suitable power
    4. A cylindrical lens only
    Show answer

    Answer: A concave lens of suitable power

    NCERT explains that a concave lens of suitable power brings the image back onto the retina in myopia, which may arise from excessive curvature of the eye lens or elongation of the eyeball.

    Source: NCERT, Class X Science: The Human Eye and the Colourful World (PDF page 3). Checked 26 October 2026.

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23. sci-023Hypermetropia (far-sightedness) is corrected using which kind of lens?

    1. A concave lens of suitable power
    2. A convex lens of suitable power
    3. A plane glass sheet
    4. A prism
    Show answer

    Answer: A convex lens of suitable power

    NCERT notes that in hypermetropia the image of nearby objects is focused beyond the retina, and a convex lens of suitable power corrects it.

    Source: NCERT, Class X Science: The Human Eye and the Colourful World (PDF page 10). Checked 26 October 2026.

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24. sci-024For a young adult with normal vision, what is the least distance of distinct vision?

    1. About 1 m
    2. About 10 cm
    3. About 25 cm
    4. About 50 cm
    Show answer

    Answer: About 25 cm

    NCERT says you must hold an object at about 25 cm from the eyes to see it comfortably and distinctly; this is the least distance of distinct vision.

    Source: NCERT, Class X Science: The Human Eye and the Colourful World (PDF page 2). Checked 26 October 2026.

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25. sci-025When white light passes through a glass prism, which colour bends the least?

    1. Blue
    2. Green
    3. Red
    4. Violet
    Show answer

    Answer: Red

    NCERT explains that different colours bend through different angles in a prism: red bends the least and violet the most, which splits white light into a spectrum.

    Source: NCERT, Class X Science: The Human Eye and the Colourful World (PDF page 7). Checked 26 October 2026.

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26. sci-026Light enters the human eye through which thin transparent membrane?

    1. Cornea
    2. Iris
    3. Optic nerve
    4. Retina
    Show answer

    Answer: Cornea

    NCERT describes the cornea as the thin membrane that forms the transparent bulge on the front of the eyeball, through which light enters.

    Source: NCERT, Class X Science: The Human Eye and the Colourful World (PDF page 1). Checked 26 October 2026.

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27. sci-027The SI unit of electric current, the ampere, is named after which scientist?

    1. Alessandro Volta
    2. André-Marie Ampère
    3. Georg Simon Ohm
    4. Michael Faraday
    Show answer

    Answer: André-Marie Ampère

    NCERT says the ampere is named after the French scientist André-Marie Ampère. One ampere is a flow of one coulomb of charge per second.

    Source: NCERT, Class X Science: Electricity (PDF page 2). Checked 26 October 2026.

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28. sci-028The volt, the SI unit of electric potential difference, is named after whom?

    1. Alessandro Volta
    2. André-Marie Ampère
    3. Charles-Augustin de Coulomb
    4. James Watt
    Show answer

    Answer: Alessandro Volta

    NCERT notes that the volt is named after the Italian physicist Alessandro Volta.

    Source: NCERT, Class X Science: Electricity (PDF page 3). Checked 26 October 2026.

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29. sci-029One kilowatt hour (kW h), the commercial "unit" of electrical energy, equals how many joules?

    1. 1 × 10⁶ J
    2. 3.6 × 10³ J
    3. 3.6 × 10⁶ J
    4. 6.0 × 10⁴ J
    Show answer

    Answer: 3.6 × 10⁶ J

    NCERT works it out: 1 kW h = 1000 W × 3600 s = 3.6 × 10⁶ watt second = 3.6 × 10⁶ joule.

    Source: NCERT, Class X Science: Electricity (PDF page 21). Checked 26 October 2026.

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30. sci-030How is a voltmeter connected in a circuit to measure potential difference?

    1. Between the cell terminals only, in series
    2. In parallel across the two points
    3. In series with the load
    4. It is never connected to a circuit
    Show answer

    Answer: In parallel across the two points

    NCERT states that a voltmeter is always connected in parallel across the points between which potential difference is to be measured.

    Source: NCERT, Class X Science: Electricity (PDF page 3). Checked 26 October 2026.

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31. sci-031Which metal is used almost exclusively for the filaments of electric bulbs?

    1. Aluminium
    2. Copper
    3. Nichrome
    4. Tungsten
    Show answer

    Answer: Tungsten

    NCERT says tungsten is used almost exclusively for bulb filaments, while copper and aluminium are generally used for electrical transmission lines.

    Source: NCERT, Class X Science: Electricity (PDF page 9). Checked 26 October 2026.

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32. sci-032Which is the smallest planet in our solar system and also the nearest to the Sun?

    1. Mars
    2. Mercury
    3. Pluto
    4. Venus
    Show answer

    Answer: Mercury

    NASA describes Mercury as the smallest planet in the solar system and the nearest to the Sun.

    Source: NASA Science, Mercury: Facts (Facts page). Checked 26 October 2026.

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33. sci-033Which planet is the hottest in our solar system, even though it is not the closest to the Sun?

    1. Jupiter
    2. Mars
    3. Mercury
    4. Venus
    Show answer

    Answer: Venus

    NASA explains that Venus's thick atmosphere traps heat in a runaway greenhouse effect, giving surface temperatures of about 467 °C, hot enough to melt lead.

    Source: NASA Science, Venus: Facts (Facts page). Checked 26 October 2026.

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34. sci-034Which planet spins slowly in the opposite direction from most planets?

    1. Mars
    2. Mercury
    3. Saturn
    4. Venus
    Show answer

    Answer: Venus

    NASA notes that Venus spins slowly in the opposite direction from most planets. NASA also says it is sometimes called Earth's twin.

    Source: NASA Science, Venus: Facts (Facts page). Checked 26 October 2026.

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35. sci-035Why does Mars look red?

    1. Iron minerals in its dirt oxidise, or rust
    2. It is covered in red ice
    3. It reflects light from Jupiter
    4. Its atmosphere is made of red sulphur gas
    Show answer

    Answer: Iron minerals in its dirt oxidise, or rust

    NASA says Mars is often called the Red Planet because iron minerals in the Martian dirt oxidise, or rust, making the surface look red.

    Source: NASA Science, Mars: Facts (Facts page). Checked 26 October 2026.

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36. sci-036Olympus Mons, the largest volcano in the solar system, is on which planet?

    1. Earth
    2. Mars
    3. Mercury
    4. Venus
    Show answer

    Answer: Mars

    NASA notes that Mars is home to Olympus Mons, which stands more than 25 miles (about 40 km) tall from base to summit.

    Source: NASA Science, Mars: Facts (Facts page). Checked 26 October 2026.

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37. sci-037Phobos and Deimos are the two small moons of which planet?

    1. Jupiter
    2. Mars
    3. Neptune
    4. Uranus
    Show answer

    Answer: Mars

    NASA says Mars has two small moons, Phobos and Deimos, which may be captured asteroids.

    Source: NASA Science, Mars: Facts (Facts page). Checked 26 October 2026.

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38. sci-038The Great Red Spot, a giant storm bigger than Earth, is found on which planet?

    1. Jupiter
    2. Mars
    3. Neptune
    4. Saturn
    Show answer

    Answer: Jupiter

    NASA describes Jupiter's Great Red Spot as a storm bigger than Earth that has raged for hundreds of years. Jupiter is also the largest planet.

    Source: NASA Science, Jupiter: Facts (Facts page). Checked 26 October 2026.

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39. sci-039Titan, a moon with methane lakes, orbits which planet?

    1. Jupiter
    2. Neptune
    3. Saturn
    4. Uranus
    Show answer

    Answer: Saturn

    NASA mentions the methane lakes on smoggy Titan and the water jets of Enceladus among the discoveries of the Saturn system.

    Source: NASA Science, Saturn: Facts (Facts page). Checked 26 October 2026.

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40. sci-040Malaria mostly spreads to people through the bites of which insects?

    1. Female Aedes mosquitoes
    2. House flies
    3. Sandflies
    4. Some infected female Anopheles mosquitoes
    Show answer

    Answer: Some infected female Anopheles mosquitoes

    WHO states that malaria mostly spreads through bites of some infected female Anopheles mosquitoes. It is caused by Plasmodium parasites.

    Source: World Health Organization, Malaria fact sheet (Fact sheet). Checked 26 October 2026.

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41. sci-041Malaria in humans is caused by which kind of organism?

    1. A bacterium
    2. A fungus
    3. A virus
    4. Plasmodium parasites
    Show answer

    Answer: Plasmodium parasites

    WHO notes that five Plasmodium parasite species cause malaria in humans.

    Source: World Health Organization, Malaria fact sheet (Fact sheet). Checked 26 October 2026.

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42. sci-042The dengue virus is transmitted to humans primarily by which mosquito?

    1. Aedes aegypti
    2. Anopheles stephensi
    3. Culex quinquefasciatus
    4. Mansonia
    Show answer

    Answer: Aedes aegypti

    WHO says dengue spreads through the bites of infected female mosquitoes, primarily Aedes aegypti, with Aedes albopictus also a vector.

    Source: World Health Organization, Dengue and severe dengue fact sheet (Fact sheet). Checked 26 October 2026.

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43. sci-043Tuberculosis is an infectious disease caused by what?

    1. A protozoan parasite
    2. A virus
    3. A vitamin deficiency
    4. Bacteria
    Show answer

    Answer: Bacteria

    WHO describes TB as an infectious disease caused by bacteria that most often affects the lungs.

    Source: World Health Organization, Tuberculosis fact sheet (Fact sheet). Checked 26 October 2026.

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44. sci-044Cholera is caused by consuming food or water contaminated with which bacterium?

    1. Mycobacterium tuberculosis
    2. Plasmodium vivax
    3. Salmonella typhi
    4. Vibrio cholerae
    Show answer

    Answer: Vibrio cholerae

    WHO defines cholera as an acute diarrhoeal infection caused by eating food or drinking water contaminated with Vibrio cholerae.

    Source: World Health Organization, Cholera fact sheet (Fact sheet). Checked 26 October 2026.

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45. sci-045India's Mars Orbiter Mission, its first interplanetary mission, was launched on which rocket?

    1. GSLV-F10
    2. LVM3-M4
    3. PSLV-C25
    4. SLV-3
    Show answer

    Answer: PSLV-C25

    ISRO records that the Mars Orbiter Mission was launched on board PSLV-C25 on 5 November 2013. Designed for six months, it completed seven years in orbit.

    Source: ISRO, Mars Orbiter Mission (Mission page). Checked 26 October 2026.

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46. sci-046Which launch vehicle carried Chandrayaan-3?

    1. GSLV-F08
    2. LVM3 (LVM3-M4)
    3. PSLV-C25
    4. SSLV-D2
    Show answer

    Answer: LVM3 (LVM3-M4)

    ISRO's Chandrayaan-3 page names the LVM3-M4 launch from Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota.

    Source: ISRO, Chandrayaan-3 details (Mission page). Checked 26 October 2026.

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47. sci-047ISRO's Aditya-L1 is an observatory placed near the Sun-Earth L1 point to study what?

    1. Earth's oceans
    2. Mars
    3. The Moon
    4. The Sun
    Show answer

    Answer: The Sun

    ISRO describes Aditya-L1 as a solar observatory, inserted into a halo orbit around the Sun-Earth L1 point.

    Source: ISRO, Aditya-L1 (Mission page). Checked 26 October 2026.

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48. sci-048How many base units does the International System of Units (SI) have?

    1. Five
    2. Nine
    3. Seven
    4. Six
    Show answer

    Answer: Seven

    BIPM lists seven SI base units: the second, metre, kilogram, ampere, kelvin, mole and candela. All other SI units can be derived from them.

    Source: BIPM, SI base units (SI base units page). Checked 26 October 2026.

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49. sci-049The candela is the SI base unit of which quantity?

    1. Amount of substance
    2. Electric charge
    3. Luminous intensity
    4. Thermodynamic temperature
    Show answer

    Answer: Luminous intensity

    BIPM lists the candela (cd) for luminous intensity, the mole for amount of substance and the kelvin for thermodynamic temperature.

    Source: BIPM, SI base units (SI base units page). Checked 26 October 2026.

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