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Everyday science: GK questions and answers

Why does iron rust? What is air made of? These questions cover the simple physics and chemistry behind daily life, with the units and instruments that every student should know.

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Ten questions picked at random from this topic, four choices each. Or go through every question as flash cards.

20 questions on everyday science

  1. What is the chemical formula of water? H₂O A water molecule has two atoms of hydrogen and one atom of oxygen.
  2. At what temperature does pure water boil at sea level? 100°C On high mountains, where air pressure is lower, water boils at a lower temperature.
  3. At what temperature does water freeze? 0°C Ice is lighter than water, which is why it floats.
  4. Which gas do plants take in to make their food? Carbon dioxide Plants give out oxygen in the process.
  5. Which gas do we need to breathe in to stay alive? Oxygen Blood carries oxygen from the lungs to every part of the body.
  6. Which gas makes up the largest part of the air? Nitrogen Air is about 78 per cent nitrogen and 21 per cent oxygen.
  7. What is the process by which green plants make food called? Photosynthesis It needs sunlight, water, carbon dioxide and the green pigment chlorophyll.
  8. What is the chemical name of common salt? Sodium chloride Its chemical formula is NaCl.
  9. Which is the hardest natural substance? Diamond Diamond is a form of carbon. So is graphite, the soft "lead" of a pencil.
  10. Which metal is liquid at room temperature? Mercury Its chemical symbol is Hg.
  11. Which is the lightest gas? Hydrogen Hydrogen is also the most plentiful element in the universe.
  12. Through which of these can sound NOT travel? Vacuum Sound needs a medium to travel.
  13. What is the SI unit of force? Newton It is named after Isaac Newton.
  14. What is the SI unit of electric current? Ampere Current is measured with an instrument called an ammeter.
  15. What is the SI unit of power? Watt One thousand watts make one kilowatt.
  16. Which instrument measures temperature? Thermometer A clinical thermometer is the kind used to measure body temperature.
  17. Which instrument measures atmospheric pressure? Barometer A fall in air pressure often means that bad weather is on the way.
  18. Which instrument records earthquakes? Seismograph The strength of an earthquake is commonly given on the Richter scale.
  19. Iron rusts in the presence of which two things? Oxygen and water Rust is iron oxide. Paint, oil or a coating of zinc keeps iron from rusting.
  20. How many colours are there in a rainbow? Seven Violet, indigo, blue, green, yellow, orange and red.

These are well-established facts, written in our own words and last checked on 11 November 2026. If your textbook says something different, follow your textbook and tell us.

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