NCERT SOLUTIONS OF CLASS 9th CHEMISTRY CHAPTER 1 MATTER IN OUR SURROUNDINGS

                          

1. Convert the following temperatures into the Celsius scale:

a ) 300 K         b)573 K

a ) 300 K = 300 -273     = 27 ^o C

b ) 573 K = 573-273      = 300 ^o C

2. Convert the following temperature to the Kelvin scale:

a ) 25  ^o C          b ) 373 ^o C 

a ) 25 ^o C   = 273+25      = 298 K

b ) 373 ^o C  = 373+273     = 646 K

3. Give reasons for the following observations:

a ) Naphthalene balls disappear with time without leaving any solid.

ANS: Naphthalene is a  volatile solid and has a tendency to sublime. Therefore, it changes into vapors  completely  which disappear into the air and no solid is left.

b ) We can get the smell of perfume sitting several meters away.

ANS: This is because perfumes contain a volatile solvent that carries pleasant-smelling vapors. They diffuse quite fast and can reach to people sitting several meters away.

4. Arrange the following substances in increasing order of forces of attraction between the particles –Water, sugar, oxygen.

ANS: Oxygen < water < sugar

5. What is the physical state of water at 

a ) 25^oC          

b ) 0^oC    

c ) 100^oC 

a ) Liquid

b ) Solid

c ) vapors (or steam )

6. Give two reasons to justify__

a ) water at room temperature is a liquid.

ANS: i. It is because water has a fixed volume but no fixed shape. It takes the shape of the container in which it is kept.

    ii. Water can flow from a higher level to a lower level.

b ) An iron almirah  is solid at room temperature.

i. it is because solids have a definite shape.

ii. It has also a fixed volume.

7. Why is ice at 273 K more effective in cooling than water at the same temperature?

ANS: Ice at 273 K is more effective in cooling than water at the same temperature because, in ice, the molecules have lower energy as compare to particles in the liquid water at the same temperature. It requires latent heat of fusion for melting.

8. What produces more several burns, boiling water or steam?

ANS: Steam produces a more severe burn as compared to boiling water. This is because, in steam, the molecules have higher kinetic energy than in boiling water. After all, the latent heat of vaporization of steam is more than that of boiling liquid. Therefore, it produces more severe burns.

9. Name A, B, C, D, E, and F in the following diagram showing the change in its state:

ANS:

A: Fusion

B: Vaporization

C: Condensation

D: Solidification

E: Sublimation

F: Sublimation

NCERT CHEMISTRY SOLUTION CHAPTER 2: