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Selina solutions concise physics class 8 icse Solutions for Chapter 6 heat transfer

Exercises in Chapter 6 heat transfer Grade 8
Questions in Objective Questions

Q4) Select the correct alternative:

(a) In evaporation

  1. All molecules of liquid begin to escape out

  2. Only the molecules at the surface escape out

  3. The temperature of liquid rises by absorbing heat from surroundings.

  4. The molecules get attracted within the liquid

(b) The rate of evaporation of a liquid increases when

  1. Temperature of liquids falls

  2. Liquid is poured in a vessel of less surface area

  3. Air is blown above the surface of liquid

  4. Humidity increases

(c) During boiling or vaporization

  1. All molecules take part

  2. Temperature rises

  3. No heat is absorbed

  4. The average kinetic energy of molecules increases.

(d) The boiling point of a liquid is increased by

  1. Increasing the volume of liquid

  2. Increasing the pressure, on liquid

  3. Adding ice to the liquid

  4. Decreasing pressure on liquid

(e) Two rods A and B of the same metal, but of length 1m and 2m respectively are heated from 0 degree celsius to 100 degree celsius. Then

  1. Both the rods A and B elongate the same

  2. The rod A elongates more than the rod B

  3. The rod B elongates more than the rod A

  4. The rod A elongates but the rod B contracts

(f) Two rods A and B of the same metal, same length, but one solid and other hollow are heated to the same rise in temperature. Then

  1. The solid rod A expands more than the solid rod B

  2. The hollow rod B expands more than the solid rod A

  3. The hollow rod B contracts but the solid rod A expands

  4. Both the rods A and B expand the same

(g) A given volume of alcohol and the same volume of water are heated from the room temperature to the same temperature then

  1. Alcohol contracts but water expands

  2. Water contracts but the alcohol expands

  3. Water expands more than alcohol

  4. Alcohol expands more than water

(h) The increase in length of a metal rod depends on

  1. The initial length of the rod only

  2. The rise in temperature only

  3. The material of rod only

  4. All the above three factors

(i) The correct statement is

  1. Iron rims are cooled before they are placed on the cart wheels

  2. A glass stopper gets tighten on warming the neck of the bottle

  3. Telephone wires sag in winter but become tight in summer

  4. A little space is left between two rails on a railway track

Questions in Short/Long Answer Questions
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