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General ScienceEasyAsked in: NDA · NDA-II 2018, GAT

Which one of the following is called dry ice?

  1. A.Solid carbon dioxide
  2. B.Liquid carbon dioxide
  3. C.Liquid nitrogen
  4. D.Liquid ammonia

Correct answer

A. Solid carbon dioxide

Explanation

The correct answer is A, Solid carbon dioxide. It is called dry ice because, at ordinary pressure, it changes directly from solid to gas (sublimation) instead of melting, so it never makes anything wet.

Dry ice is made by compressing and cooling carbon dioxide gas until it liquefies, then letting the liquid expand quickly so that part of it freezes into a snow that is pressed into blocks or pellets. It stays at about −78.5°C, much colder than water ice, and is used to transport frozen foods and medical samples, for blast cleaning, and to create fog effects when dropped into warm water.

B is wrong because liquid carbon dioxide exists only under high pressure and is not called dry ice; it is used in some fire extinguishers.

C is wrong because liquid nitrogen, at about −196°C, is a liquid used for cryopreservation, not a solid.

D is wrong because liquid ammonia is used as a refrigerant and a solvent, and has no such name.

Exam tip: dry ice = solid CO₂, sublimes at −78.5°C; liquid nitrogen boils at −196°C.

Practice Questions

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Q1.General ScienceAsked in: UPSC Civil Services · CSE Prelims 2022, GS Paper IMedium

Which of the following are nitrogen-fixing plants?

1. Alfalfa

2. Amaranth

3. Chickpea

4. Clover

5. Purslane (Kulfa)

6. Spinach

Select the correct answer using the code given below:

  1. A.1, 3 and 4 only
  2. B.1, 3, 5 and 6 only
  3. C.2, 4, 5 and 6 only
  4. D.1, 2, 4, 5 and 6
Show answer
Correct answer: A. 1, 3 and 4 only

Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.

Q2.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

The mass number of an element is NOT changed when it emits

  1. A.Alpha and Beta radiations only
  2. B.Alpha and Gamma radiations only
  3. C.Beta and Gamma radiations only
  4. D.Alpha, Beta and Gamma radiations
Show answer
Correct answer: C. Beta and Gamma radiations only

Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.

Q3.General ScienceAsked in: UPSC CAPF · CAPF 2025, Paper IMedium

Which one among the following statements about facilitated transport in plants is correct?

  1. A.All passive transports are types of facilitated transport.
  2. B.Facilitated transport is an example of active transport.
  3. C.Water moves across plasma membrane by active transport.
  4. D.Facilitated transport requires assistance of carrier proteins.
Show answer
Correct answer: D. Facilitated transport requires assistance of carrier proteins.

In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.

Q4.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?

  1. A.Richard Feynman
  2. B.Murray Gell-Mann
  3. C.Albert Einstein
  4. D.Niels Bohr
Show answer
Correct answer: B. Murray Gell-Mann

The American physicist Murray Gell-Mann proposed quarks in 1964 and gave them their name. Gell-Mann, and independently George Zweig, suggested that protons, neutrons and other such particles are built from smaller units.