Available Answers

1. 1.

   Write true or false. Correct the false statements.

   1. Boiling causes cooling.
   2. Wet clothes dry because the water in them boils to its vapour state.
   3. Boiling occurs in the whole volume of a liquid whereas evaporation occurs only at the surface of a liquid.
   4. Water evaporates at all temperatures.
2. 2.

   Tick the most appropriate answer.

   1. The process that occurs when water changes into water vapours at 30ºC is called

   1. cubical expansion.
   2. boiling.
   3. evaporation.
   4. superficial expansion.

   2. Evaporation causes

   1. heating.
   2. boiling.
   3. melting.
   4. cooling.

   3. The length of an iron rod increases from 10 m to 11 m, when kept over a bumer flame. This increase in length is due to

   1. cubical expansion.
   2. linear expansion.
   3. superficial expansion.
   4. solidification.

   4. There are four iron rods R₁, R₂, R₃, R₄ to 1000ºC and that of R₄ to 800ºC. Which rod will have the maximum linear expansion?

   1. R₁
   2. R₂
   3. R₃
   4. R₄

   5. The liquid that expands the minimum on heating is

   1. benzene.
   2. water.
   3. alcohol.
   4. ether.

   6. The factors on which linear expansion depend on are

   1. original length of the solid.
   2. increase in the temperature of the solid.
   3. nature of the solid.
   4. all of these

   7. The type of thermal expansion that takes place in gases is

   1. linear expansion.
   2. superficial expansion.
   3. cubical expansion.
   4. all of these
3. 3.

   Fill in the blanks.

   1. Evaporation occurs only at the __________________________________ of a liquid.
   2. Expansion in ___________________________________ of a solid heating is called superficial expansion.
   3. The process of ______________________________ occurs at the boiling points of a liquid.
   4. Boiling is a __________________________________ process.
   5. Brass expands __________________________________ than steel.
   6. _____________________________________ expand more than liquids.
   7. A 20 m steel rod water expands __________________________ than a 80 m steel rod, when heated to 500ºC for 10 minutes.
   8. The density of water is maximum at ___________________.
4. 4.

   Match the columns.

   1. Expansion in length	a. evaporation
   2. Water to water vapour at 100ºC	b. linear expansion
   3. Expansion in volume	c. boiling
   4. Expansion in area	d. cubical expansion
   5. Water to water vapour at 25ºC	e. sublimation

    

5. 5.

   Write true or false. Correct the false statements.

   1. During the process of boiling, the temperature of the liquid remains constant.
   2. Evaporation is a slow and silent process.
   3. Water in earthen pots remains cool due to thermal expansion.
   4. most of the substances decrease in their dimensions on heating.
   5. Superficial expansion can only occur in solids and liquids.
   6. Gravesande's ring and ball experiment shows that liquids expand on heating.
   7. Glass is a good conductor of heat.
   8. Out of solids, liquids and gases, gases expand the most.
6. 6.

   Define Evaporation.