Assertion and Reason for Ch 1 Matter in Our Surroundings Class 9 Science
Important QuestionsA
Directions : In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
Answer
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion(A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
1
Reason (R): It is proper to regard the gaseous state of ammonia as vapours.
Answer
(c) Assertion (A) is true but reason (R) is false.
It is not proper to regard ammonia in gaseous state as vapour because ammonia is not liquid at room temperature.
2
Reason (R): The conversion of a solid directly into gas is called condensation.
Answer
(c) Assertion (A) is true but reason (R) is false.
The conversion of a solid directly into gas is called sublimation.
3
Reason (R): The boiling point of water increases at high altitudes.
Answer
(d) Assertion (A) is false but reason (R) is true.
It is difficult to cook food at high altitudes since the boiling point of water decreases at high altitudes and it does not provide sufficiently high temperature to the food to get cooked.
4
Reason (R): Kinetic energy of the molecules is inversely proportional to absolute temperature.
Answer
(d) Assertion (A) is false but reason (R) is true.
During evaporation of liquids, the temperature decreases due to escape of molecules with high energy. Kinetic energy of the molecules is directly proportional to absolute temperature.
5
Reason (R): All solids are first converted to liquids and then to gases on heating.
Answer
(c) Assertion (A) is true but reason (R) is false.
Certain solids directly change to the gaseous state upon heating without passing through the liquid state. This process is called sublimation.
6
Reason (R): The density of both water and ice is same.
Answer
(c) Assertion (A) is true but reason (R) is false.
Ice floats of the surface of water because the density of water is more than ice. Ice is lighter than water due to open spaces in its crystalline structure.
7
Reason (R): The heat supplied is absorbed either as latent heat of fusion or as latent heat of vaporisation.
Answer
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion
(A).
The heat supplied during the state transformation does not increase the kinetic energy but is absorbed for conversation of complete solid to liquid or complete liquid to vapours.
8
Reason (R): The heat supplied is absorbed either as latent heat of fusion or as latent heat of vaporisation.
Answer
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion
(A).
The heat supplied during the state transformation does not increase the kinetic energy but is absorbed for conversion of complete solid to liquid or complete liquid to vapours.
9
Reason(R) : Naphthalene leaves residue when kept open for some time.
Answer
(d) Assertion (A) is false but reason (R) is true.
The conversion of a gas directly into solid is called de – sublimation. Naphthalene does not leave any residue when kept open for some time.
10
Reason(R) : Intermolecular forces are greater in gases.
Answer
(c) Assertion (A) is true but reason (R) is false.
Liquids diffuse slowly as compared to gases. Liquids have stronger intermolecular forces as compared to gases hence liquid molecules are less free to move than gases.