Revision Notes for Science Chapter 1 - Matter in our surroundings (Class 9th) | askIITians

NCERT Most Important question & Solutions for class-9 Chapter-1 Matter in Our Surrounding (Chemistry)

The start of class 9 marks the beginning of the foundation for class 11 and class 12. It is very important study the basics in order to understand each and every chapter properly. In this page, we have provided all the important question for cbse class 9 that could be asked in the examination. Students also need to study the ncert solutions for class 9 in order to gain more knowledge and understanding the lessons. Questions and Answers are way to learn the new things in a proper way. NCERT textbooks downloads for class 9 in pdf are also available for the students if they need more help. By downloading these books, they can study from it. Our experts also prepared revision notes for class 9 so that students should see the details of each and every chapters. Class 9 important questions are the best to revise all the chapters in the best way.

1. Arrange the three states of matter in the increasing order of: (i) rate of diffusion(ii) particle motion.
Answer
(i) Rate of diffusion: solid < liquid < gas.

(ii) Particle motion: solid < liquid < gas

2.Explain why heat energy is needed to melt a solid. Define latent heat of fusion.
Answer
Heat energy is needed to melt a solid because there exist forces of attraction between the particles of solid. The heat energy helps in overcoming the forces of attraction between the particles and thus helps in melting a solid.Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at atmospheric pressure at its melting point.

3.Why does the temperature remain constant during the change of state of matter? Explain it on the basis of change of solid state into liquid state.

Answer

The temperature remains constant as the heat gets used up in changing the state by overcoming the forces of attraction between the particles.For example, a solid melts on heating. Its temperature does not rise until the entire solid is converted into liquid. This heat energy gets hidden into the contents and is known as the latent heat.

4.List any four factors on which evaporation depends. Explain in short any three factors.

Answer
 
The rate of evaporation depends on following factors:
(i) Surface area exposed to atmosphere
(ii) Temperature
(iii) Humidity
(iv) Wind speed
 
(i) Surface area exposed to atmosphere: Since evaporation is a surface phenomenon, therefore, it increases with an increase in surface area.
 
(ii) Humidity: The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount of water in air is already high, the rate of evaporation decreases. So, evaporation decreases with increase in humidity.
 
(iii) Wind speed: With the increase in wind speed, the particles of water vapour move away with the wind, decreasing the amount of water vapour in the surroundings. This results in a faster rate of evaporation. So, evaporation increases with the increase in wind speed.
 
5.Arrange the following matters in the increasing order of
(i) force of attraction
(ii) intermolecular space: 
Matters: iron nail, kerosene and oxygen gas.
 
Answer
 (i) Force of attraction: Oxygen gas < Kerosene < Iron nail
(ii) Intermolecular space: Iron nail < Kerosene < Oxygen gas
 
6.Define the following terms:
(i) Rigidity, (ii) Compressibility, (iii) Diffusion.
 
Answer
(i) Rigidity: It is the property of matter to maintain shape against external force.
(ii) Compressibility: It is the property of matter by virtue of which molecules of matter are brought closer to each other.
(iii) Diffusion: The inter mixing of the particles of matter is known as diffusion.
 
7.Camphor disappears without leaving any residue. Explain?
 
Answer
 
Camphor disappears without leaving any residue because of sublimation, as it changes its state directly from solid to gas without changing to liquid.
 
8.At which the solid and liquid states of substance can exist together?
 
Answer 0°C
 
9.What are the characteristics of particles of matter?

Answer

The characteristics of particles of matter are:
→ Particles of matter have spaces between them.
→ Particles of matter are continuously moving.
→ Particles of matter attract each other.
 
10.Tabulate the differences in the characteristics of states of matter.
 
Answer
 
 
Property
Solid-state
Liquid state
Gaseous state
 
 Definite shape and volume. No definite shape. Liquids attain the shape of the vessel in which they are kept. Gases have neither a definite shape nor a definite volume.
2.
 Incompressible Slightly Compressible  Highly compressible
3.
 Cannot flow Can flow Can flow
4.
 Particles don’t move freely Particles move freely but are confined within the boundary. Particles move freely.
5.
 Force of attraction between particles is maximum. Force of attraction between particles is less than solid but more than that in gas Force of attraction between particles is least.

11. Convert the following temperature to Celsius scale:

(a) 300 K
► 300 K = (300 – 273)°C
= 27°C
(b) 573 K► 573 K = (573 – 273)°C
= 300°C

12.Why does our palm feel cold when we put some acetone or petrol or perfume on it?

ANSWERS

Acetone, petrol, and perfume evaporate at low temperatures. When some acetone, petrol, or perfume is dropped on the palm, it takes heat from the palm and evaporates, thereby making the palm cooler.

13.Give reason for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.

Answer

(a) Naphthalene balls disappear with time without leaving any solid because of they undergoes sublimation easily i.e., the change of state of naphthalene from solid to gas takes place easily.

(b) Perfumes have high degree of vaporisation and its vapour diffuses into the air easily. Therefore, we can get the smell of perfume sitting several metres away.

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


Answer

NCERT Quick Revision Notes For Chapter-1 Matter in Our Surrounding

NCERT Solution For Chapter-1 Matter in Our Surrounding

NCERT MCQs For Chapter-1 Matter in Our Surrounding

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