# CBSE Class 9, Matter in Our Surroundings - Answers of NCERT Science Chapter 1 Exercise Questions

### CBSE Board Class 9, NCERT Science (Chemistry)

#### Answers of NCERT Science textbook exercise important questions only

Question.1: Convert the following temperatures into the Celsius scale.
(a) 300 K   (b) 573 K
(a) 300 K = 300 - 273 = 27OC
(b) 573 K = 573 - 273 = 300OC
Question.2: Convert the following temperatures into the Kelvin scale. (a) 25OC (b) 373OC
(a) 25OC = 25 + 273 = 298 K
(b) 373OC = 373 + 273 = 646 K
Question.3: Give reasons for the following observations.
(a) Naphthalene balls disappear with time without leaving       any solid.
(b) We can get the smell of perfume sitting several meters       away.
(a) Naphthalene shows the property of sublimation. Evaporation of naphthalene takes place easily and so it disappears during course of time without leaving a solid.
(b) Perfumes vaporize very fast and its vapors diffuse into air easily. That is why we can smell perfume sitting several meters away.
Question.4: Arrange the following in increasing order of forces of attraction between the particles - water, sugar, oxygen.
Oxygen < Water < Sugar.
Question.6: Give two reasons to justify:
(a)   Water at room temperature is a liquid.
(b)   An iron almirah is a solid at room temperature.