NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings


NCERT Solutions for Class 9 Science Chapter 1, “Matter in Our Surroundings,” provide comprehensive answers to exercises, aiding students in understanding fundamental concepts like states of matter, diffusion, and physical changes. These solutions, aligned with NCERT guidelines, facilitate effective learning and problem-solving, crucial for a strong foundation in science.

1. Convert the following temperature to Celsius scale.

(a) 293K                (b) 470K



(a) 293K= (293 – 273)°C = 20°C

(b)  470K= (470 – 273)°C = 197°C

2.Convert the following temperatures to the Kelvin scale.

(a) 25°C                (b) 373°C


0°C = 273K

(a) 25°C = (25+273)K = 298K

(b) 373°C = (373+273)K = 646K

3. Give reason for the following observations:

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

(b) We can get the smell of perfume while sitting several metres away.


(a) At room temperature, naphthalene balls undergo sublimation wherein they directly get converted from a solid to a gaseous state without having to undergo the intermediate state, i.e., the liquid state.

(b) Molecules of air move at a higher speed and have large intermolecular spaces. Perfumes comprise substances that are volatile, which scatter quickly in air, becoming less concentrated over a distance. Hence, we are able to smell perfume sitting several metres away.

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


Oxygen (gas) < water (liquid) < sugar (solid)

5. What is the physical state of water at –  

(a) 25°C (b) 0°C (c) 100°C?


(a) At 25°C, the water will be in liquid form (normal room temperature)

(b) At 0°C, the water is at its freezing point, hence both solid and liquid phases are observed.

(c) At 100°C, the water is at its boiling point, hence both liquid and gaseous states of water (water vapour) are observed.

6. Give two reasons to justify –

(a) Water at room temperature is a liquid.

(b) An iron almirah is a solid at room temperature.


(a) Water persists as a liquid at room temperature since its melting point is lower than room temperature and its boiling point (100C) is higher. 


(i). A fixed volume is occupied by a fixed mass of water.

(ii). At room temperature, water does not have a fixed shape and flows to fit the container’s shape.

As a result, water is a liquid at room temperature.

(b) Because its melting and boiling points are above room temperature, an iron almirah is a solid at room temperature. In the same way, 

(i) An iron almirah is rigid and has a predetermined shape.

(ii) Metals have a relatively high density.

As a result, at room temperature, iron almirah is a solid.

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


At 273 K, ice will absorb heat energy or latent heat from the medium to overcome fusion and transform into water. As a result, ice has a greater cooling impact than water at the same temperature since water does not absorb the excess heat from the medium.

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


Steam produces severe burns. It is because it is an exothermic reaction that releases a high amount of heat which it had consumed during vaporization.

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


Interconversion of three states of matter: Using temperature or pressure, any state of matter can be turned into another.

(A) Solid to Liquid → Melting (or) fusion (or) liquefaction

(B) Liquid to Gas → Evaporation (or) vaporization

(C) Gas to liquid → Condensation

(D) Liquid to Solid → Solidification

(E) Solid to Gas → Sublimation

(F) Gas to Solid → solidification

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