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Science in everyday life MCQ with Answers

10 questionswith explanationsfor RAS, Patwari, VDO and other Rajasthan exams

Questions

Q1

The Sun appears reddish at sunrise and sunset mainly because:

  1. (1)The Sun emits more red light in the morning and evening
  2. (2)Red light is refracted most strongly near the horizon
  3. (3)Sunlight crosses more air, so most blue light is scattered away
  4. (4)Dust near the ground absorbs every colour except red

Answer: (3) Sunlight crosses more air, so most blue light is scattered away

Explanation

Near the horizon sunlight travels a longer path through the air; shorter (blue) wavelengths are scattered out, leaving mostly red light to reach the eye.

Q2

During a thunderstorm, the flash of lightning is seen before the thunder is heard because:

  1. (1)Lightning is produced before the thunder
  2. (2)Light travels much faster than sound
  3. (3)Clouds hold back the sound for a while
  4. (4)The eye responds faster than the ear

Answer: (2) Light travels much faster than sound

Explanation

Lightning and thunder are produced together, but light (about 3 × 10^8 m/s) travels far faster than sound in air (about 343 m/s), so the flash reaches us first.

Q3

In a domestic refrigerator, the inside is cooled mainly because the refrigerant:

  1. (1)Releases latent heat as it condenses in the freezer
  2. (2)Cools down when it is compressed inside the cabinet
  3. (3)Gives out heat to the air inside the cabinet
  4. (4)Absorbs latent heat as it evaporates in the evaporator

Answer: (4) Absorbs latent heat as it evaporates in the evaporator

Explanation

The liquid refrigerant evaporates in the evaporator coils inside, taking latent heat from the contents; it releases that heat outside in the condenser coils.

Q4

Consider the following statements: 1. An LED bulb converts a larger fraction of electrical energy into heat than a CFL of similar brightness. 2. A CFL contains a small amount of mercury vapour. Which of the statements given above is/are correct?

  1. (1)1 only
  2. (2)2 only
  3. (3)Both 1 and 2
  4. (4)Neither 1 nor 2

Answer: (2) 2 only

Explanation

LEDs (electroluminescence in a semiconductor) are more efficient and waste less energy as heat than CFLs; CFLs contain mercury vapour, so they need careful disposal.

Q5

Household microwave ovens usually operate at a frequency of about:

  1. (1)2.45 GHz
  2. (2)2.45 MHz
  3. (3)2.45 kHz
  4. (4)2.45 THz

Answer: (1) 2.45 GHz

Explanation

Domestic microwave ovens use microwaves of about 2.45 GHz, which make water molecules in food oscillate and heat up.

Q6

Consider the following statements about soap: 1. Soaps are sodium or potassium salts of long-chain fatty acids. 2. In a micelle, the hydrocarbon tails of soap molecules point outward towards the water. 3. Soap forms an insoluble scum with hard water. Which of the statements given above is/are correct?

  1. (1)1 and 2 only
  2. (2)2 and 3 only
  3. (3)1 and 3 only
  4. (4)1, 2 and 3

Answer: (3) 1 and 3 only

Explanation

In a micelle the water-repelling hydrocarbon tails point inward into the oil, while the ionic heads face the water; calcium and magnesium in hard water form scum with soap.

Q7

Temporary hardness of water, which can be removed by boiling, is caused by the presence of dissolved:

  1. (1)Chlorides of calcium and magnesium
  2. (2)Sulphates of calcium and magnesium
  3. (3)Bicarbonates of calcium and magnesium
  4. (4)Carbonates of sodium and potassium

Answer: (3) Bicarbonates of calcium and magnesium

Explanation

Boiling turns calcium and magnesium bicarbonates into insoluble carbonates that settle out; chlorides and sulphates cause permanent hardness.

Q8

The non-stick coating on cookware is commonly made of:

  1. (1)Polyvinyl chloride (PVC)
  2. (2)Bakelite
  3. (3)Polystyrene
  4. (4)Polytetrafluoroethylene (Teflon)

Answer: (4) Polytetrafluoroethylene (Teflon)

Explanation

PTFE (Teflon), a polymer of tetrafluoroethylene, is heat-resistant and has a very low-friction surface, so food does not stick.

Q9

In an ordinary zinc-carbon dry cell (Leclanché type) used in torches, which part acts as the positive electrode?

  1. (1)Zinc container
  2. (2)Carbon rod
  3. (3)Copper strip
  4. (4)Ammonium chloride paste

Answer: (2) Carbon rod

Explanation

The zinc container is the negative electrode and the central carbon rod, surrounded by manganese dioxide, is the positive electrode; the ammonium chloride paste is the electrolyte.

Q10

The 2019 Nobel Prize in Chemistry was awarded for the development of which type of battery, now used in mobile phones and laptops?

  1. (1)Lithium-ion battery
  2. (2)Nickel-cadmium battery
  3. (3)Lead-acid battery
  4. (4)Sodium-sulphur battery

Answer: (1) Lithium-ion battery

Explanation

John Goodenough, M. Stanley Whittingham and Akira Yoshino shared the 2019 Chemistry Nobel for developing lithium-ion batteries.