Class 9 Science


Exemplar Problem

Short Answer Questions

Part 1

Question 11: A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C? Comment.

Answer: The boiling point of pure water is 1000C. Soluble impurities increase the boiling point of a liquid. As the sample of water boils at 1020C, hence it is not pure. Impurities does not affect the freezing point, hence the given sample of water will freeze at 00C.

Question 12: A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following (Fig. 1.1) would correctly represent the result? Justify your choice.

Temperature Time Graphs

Answer: Figure (d) represents the result correctly.

Explanation: Initially temperature of the content of beaker does not rise, because of latent heat of fusion. When all ice melts and, the temperature of content starts rising, hence, figure (d) represents the result correctly.

Question 13: Fill in the blanks:

  1. Evaporation of a liquid at room temperature leads to a __________ effect.
  2. At room temperature the forces of attraction between the particles of solid substances are __________ than those which exist in the gaseous state.
  3. The arrangement of particles is less ordered in the _________ state. However, there is no order in the _______ state.
  4. _____________ is the change of gaseous state directly to solid state without going through the _____________ state.
  5. The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ___________.

Answer: (a) Cooling (b) Stronger (c) liquid, gaseous (d) sublimation, liquid (e) evaporation

Question: -14 - Match the physical quantities given in column A to their S I units given in column B :

Column AColumn B
(1) Pressure(a) Cubic meter
(2) Temperature(b) Kilogram
(3) Density(c) Pascal
(4) Mass(d) Kelvin
(5) Volume(e) Kilogram per cubic meter

Answer: (1) c, (2) d, (3) e, (4) b, (5) a

Question 15: The non S I and S I units of some physical quantities are given in column A and column B respectively. Match the units belonging to the same physical quantity:

Column AColumn B
(1) Degree Celsius(a) Kilogram
(2) Centimeter(b) Pascal
(3) Gram per centimeter cube(c) Meter
(4) Bar(d) Kelvin
(5) Milligram(e) Kilogram per meter cube

Answer: (1) d, (2) c, (3) e, (4) b, (5) a