Common General Science
Everyday Science — Practical Facts
15 questions on science in daily life — cooking, cleaning, weather, technology.
Everyday Science — Practical Facts
15 questions · 8 minutes
08:00
Q1.Soap works by:
Explanation: Soap molecules have a hydrophilic (water-loving) and hydrophobic (oil-loving) end, emulsifying dirt in water.
Q2.Why does ice float on water?
Explanation: Water expands when it freezes (anomalous expansion), making ice less dense than liquid water. Maximum density at 4°C.
Q3.Pressure cooker cooks faster because:
Explanation: Higher pressure raises the boiling point of water above 100°C, cooking food faster.
Q4.Rainbow is caused by:
Explanation: Rainbow = sunlight dispersed (split into colours) and internally reflected inside raindrops.
Q5.Why is the sky blue?
Explanation: Rayleigh scattering: shorter wavelength blue light is scattered more by atmospheric molecules.
Q6.LPG (cooking gas) mainly contains:
Explanation: LPG = Liquefied Petroleum Gas, mainly Butane (C₄H₁₀) and Propane (C₃H₈).
Q7.The smell added to LPG for leak detection is:
Explanation: Ethyl mercaptan (a foul-smelling compound) is added to odourless LPG so leaks can be detected.
Q8.Why do we add salt to icy roads?
Explanation: Salt lowers the freezing point of water (freezing point depression), causing ice to melt.
Q9.A mirage is seen in deserts due to:
Explanation: Hot air near the ground has lower density → light bends (total internal reflection) → creates illusion of water.
Q10.CFL stands for:
Explanation: CFL = Compact Fluorescent Lamp. More energy-efficient than incandescent bulbs but being replaced by LEDs.
Q11.Hard water does not form lather because it contains:
Explanation: Hard water contains dissolved calcium and magnesium salts that react with soap, preventing lather.
Q12.Rusting requires:
Explanation: Rusting = iron + oxygen + moisture → iron oxide (Fe₂O₃). Both O₂ and H₂O are needed.
Q13.Why does a ball thrown upward come back?
Explanation: Earth's gravitational force pulls objects toward its centre. The ball decelerates, stops, and falls back.
Q14.The gas used in balloons to make them float is:
Explanation: Helium is lighter than air (second lightest element after hydrogen) and non-flammable, making it safe for balloons.
Q15.Why do we feel cool when we sweat?
Explanation: Evaporation is a cooling process — sweat absorbs body heat when it evaporates, cooling the skin.
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