In Text Questions Page Number 6 Chapter 1 Science Class 9 NCERT Solutions in Text Question Chapter 1 Matter in Our

In text questions page number 6

Question 1. The mass per unit volume of a substance is called density. (Density = mass/volume).
Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton and iron.
Answer: Arrangement of the above matters in order of increasing density
Air<exhaust from chimney<cotton<water<honey<chalk<Iron

Question 2. (a) Tabulate the differences in the characteristics of states of matter.
(b) Comment upon the following:
rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Answer: (a)

S.NO	Property	Solid	Liquid	Gases
1.	Shape	They Have definite shape	They do not have definite shape	They do not have definite shape
2.	Volume	They have definite volume	They do not have definite volume	They do not have definite volume
3.	Density	They have high density.	Liquids have less density than solids.	Liquids have least density.
4.	Kinetic energy of particles.	Least	More than solids	Maximum
5.	Compressibility	Negligible	Low	High

Rigidity: It is the property of matter to resist the change of its shape.
Compressibility: It is the property of matter in which its volume is decreased by applying force.
Fluidity: It is the ability of matter to flow.
Filling a gas container: On filling a gas takes the shape of the container.
Shape: Having definite boundaries.
Kinetic energy: It is the energy possessed by the particles of matter due to its motion.
Density: It is the ratio of mass with per unit volume

Question 3. Give reasons                                                                                           
(a) A gas fills completely the vessel in which it is kept.                                 
(b) A gas exerts pressure on the walls of the container.                               
(c) A wooden table should be called a solid.                                                 
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.
Answer:

(a) A gas fills completely the vessel in which it is kept because the particles of gas move freely and acquire the shape of the container.
(b) A gas exerts pressure on the walls of the container because particles of gas move freely and randomly due to which they hit the boundaries of the container and exert the force on its wall.
(c) A wooden table has a definite shape and definite volume and hence it is called solid.
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert because there is lot of empty space between the particles of gas but it not so in case of solids.

Quesiton 4. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Answer: Ice in fact it is solid but it has cage like structure and hence its molecules have more empty space as compared to water so it has smaller density then water and hence floats on water.