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Heat

179 MCQ questions with answers and explanations · page 6 of 8

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Q126. Water kept in an earthen pot cools down during summer days due to the following phenomenon-

  1. Adiffusion
  2. Btranspiration
  3. COsmosis
  4. Devaporation
Show answer & explanation

Answer: D) evaporation

Q127. When two pieces of ice are pressed together, they stick together because-

  1. AThe melting point of ice decreases due to increased pressure.
  2. BDue to high pressure, the melting point of ice increases.
  3. CDue to high pressure, the melting point of ice first decreases and then increases.
  4. DThere is no relation between pressure and melting point.
Show answer & explanation

Answer: A) The melting point of ice decreases due to increased pressure.

Q128. Ice skating demonstrates that increasing the pressure lowers the melting point of ice.

  1. Aincreases
  2. Bremains unchanged
  3. Chappens to
  4. Dfirst decreases then increases
Show answer & explanation

Answer: C) happens to

Q129. A piece of ice is floating in a glass full of water. The piece has completely melted.

  1. Aincreases
  2. Bhappens to
  3. Cremains unchanged
  4. Dnone of these
Show answer & explanation

Answer: C) remains unchanged

Q130. Food gets cooked in less time in a pressure cooker because-

  1. Athe boiling point of water increases
  2. Bthe boiling point of water decreases
  3. CFood takes in less heat
  4. Dneither of the above
Show answer & explanation

Answer: A) the boiling point of water increases

Q131. Humans feel discomfort due to humidity. Which of the following is a suitable reason for this?

  1. Aexcessive sweating
  2. BReduced sweating
  3. CSweat not evaporating due to humidity
  4. Dnone of the above
Show answer & explanation

Answer: C) Sweat not evaporating due to humidity

Q132. What is the process called when a liquid changes into its vapor before its boiling point?

  1. Aevaporation
  2. Bcompaction
  3. Cfreezing
  4. Dnone of these
Show answer & explanation

Answer: A) evaporation

Q133. Water starts boiling in the mountains at the following temperature-

  1. Aless than 100°C
  2. BMore than 100°C
  3. C100°C
  4. Dnone of these
Show answer & explanation

Answer: A) less than 100°C

Q134. The heat emitted or absorbed which changes the state of matter but does not cause any change in temperature is called—

  1. Aspecific heat
  2. Babsorbed heat
  3. Cheat emitted
  4. Dlatent heat
Show answer & explanation

Answer: D) latent heat

Q135. The heat required to convert a unit mass of a solid substance from solid to liquid at its melting point is called-

  1. Amelting point of a solid
  2. Bboiling point of a solid
  3. Clatent heat of fusion of a solid
  4. Devaporation
Show answer & explanation

Answer: C) latent heat of fusion of a solid

Q136. The value of latent heat of fusion of ice is-

  1. A0.8 Cal/g
  2. B8 Cal/g
  3. C80 Cal/g
  4. D536Cal/g
Show answer & explanation

Answer: C) 80 Cal/g

Q137. The latent heat of vapor is-

  1. A536 Cal/g
  2. B336 Cal/g
  3. C542 Cal/g
  4. D340 Cal/g
Show answer & explanation

Answer: A) 536 Cal/g

Q138. Steam burns hands more than boiling water because-

  1. ASteam has latent heat
  2. BSteam penetrates the body
  3. CSteam has more firepower
  4. DSteam is light
Show answer & explanation

Answer: A) Steam has latent heat

Q139. The first law of thermodynamics conserves

  1. AImpulse
  2. Benergy
  3. Cboth momentum and energy
  4. Dnone of these
Show answer & explanation

Answer: B) energy

Q140. The concept of internal energy is derived from which law of thermodynamics?

  1. Azero number rule
  2. BFirst Law
  3. CSecond Law
  4. DThird Law
Show answer & explanation

Answer: B) First Law

Q141. In Adiabatic Change-

  1. Aheat remains unchanged
  2. Btemperature remains unchanged
  3. CBoth heat and temperature change
  4. Dnone of these
Show answer & explanation

Answer: A) heat remains unchanged

Q142. In isothermal change-

  1. Aheat remains unchanged
  2. Btemperature remains unchanged
  3. CBoth heat and temperature change
  4. Dnone of these
Show answer & explanation

Answer: B) temperature remains unchanged

Q143. The function of the thermostat in a refrigerator is-

  1. ALowering the temperature
  2. Bincrease freezing temperature
  3. Cmaintaining a consistent temperature
  4. DDecreasing the melting point
Show answer & explanation

Answer: C) maintaining a consistent temperature

Q144. The first law of thermodynamics is generally concerned with what?

  1. ACharles's Law
  2. BLaw of conservation of energy
  3. CLaws of heat exchange
  4. DNewton's law of cooling
Show answer & explanation

Answer: B) Law of conservation of energy

Q145. The temperature of the surface of the Sun is-

  1. A600K
  2. B2000K
  3. C6000K
  4. D7000K
Show answer & explanation

Answer: C) 6000K

Q146. Which of the following changes occurs when salt is added to water?

  1. Aboiling point increases and freezing point decreases
  2. Bthe boiling point decreases and the freezing point increases
  3. CBoth boiling point and freezing point decrease
  4. DBoth boiling point and freezing point increase.
Show answer & explanation

Answer: A) boiling point increases and freezing point decreases

Q147. Running a fan in hot weather gives relief because-

  1. AThe fan gives cool air.
  2. BOur sweat evaporates faster.
  3. COur bodies radiate more heat
  4. DThe conductivity of air increases.
Show answer & explanation

Answer: B) Our sweat evaporates faster.

Q148. The room can be cooled by-

  1. Aby the flow of water
  2. Bby releasing compressed gas
  3. Cfrom cooking gas
  4. Dby melting a solid
Show answer & explanation

Answer: B) by releasing compressed gas

Q149. A body absorbs maximum heat when it is-

  1. Ablack and rough
  2. Bblack and smooth
  3. Cwhite and rough
  4. Dwhite and smooth
Show answer & explanation

Answer: A) black and rough

Q150. At what point is the Fahrenheit temperature twice the centigrade temperature?

  1. A-6.7°F
  2. B-12.3°F
  3. C135°P
  4. D160°F
Show answer & explanation

Answer: D) 160°F

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