Class 9 Science - Chapter 1: question and answer based on NCERT
This page provides a complete, easy-to-read set of NCERT questions and answers for “Matter in Our Surroundings” aligned with the latest CBSE curriculum. Discover accurate and simple explanations covering key concepts like the classification of matter, its states, properties, and changes of state. Perfect for students across India to understand this important chapter thoroughly and score well in their CBSE Class 9 Science exam.
📚 NCERT Textbook Questions and Detailed Answers
1
Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Answer: Matter includes: Chair, air, almonds, cold, lemon water, and smell of perfume. Not matter: Love, hate, thought.
Answer: Matter includes: Chair, air, almonds, cold, lemon water, and smell of perfume. Not matter: Love, hate, thought.
2
The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go closer. Why?
Answer: Particles of hot food have higher kinetic energy and diffuse quickly through the air. Particles of cold food have lower energy and diffuse slowly.
Answer: Particles of hot food have higher kinetic energy and diffuse quickly through the air. Particles of cold food have lower energy and diffuse slowly.
3
A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer: This shows that matter is made up of tiny particles with spaces between them, allowing the diver to move through the water.
Answer: This shows that matter is made up of tiny particles with spaces between them, allowing the diver to move through the water.
4
What are the characteristics of the particles of matter?
Answer: Particles have spaces between them, are in constant motion, attract each other, and have mass.
Answer: Particles have spaces between them, are in constant motion, attract each other, and have mass.
5
Convert the following temperatures to Celsius scale:
(a) 300 K = 300–273.15 = 26.85 °C
(b) 573 K = 573–273.15 = 299.85 °C
(a) 300 K = 300–273.15 = 26.85 °C
(b) 573 K = 573–273.15 = 299.85 °C
6
What is the physical state of water at:
a) 250 °C: Gas (steam)
b) 100 °C: Boiling point (transition between liquid and gas).
a) 250 °C: Gas (steam)
b) 100 °C: Boiling point (transition between liquid and gas).
7
Why does the temperature remain constant during the change of state?
Answer: The heat is used to overcome the forces of attraction between particles (latent heat), not to raise the temperature.
Answer: The heat is used to overcome the forces of attraction between particles (latent heat), not to raise the temperature.
8
Suggest a method to liquefy atmospheric gases.
Answer: By applying high pressure and lowering the temperature.
Answer: By applying high pressure and lowering the temperature.
9
Why does a desert cooler work better on a hot, dry day?
Answer: In dry air, water evaporates quickly, extracting more heat and cooling the air efficiently.
Answer: In dry air, water evaporates quickly, extracting more heat and cooling the air efficiently.
10
How does water kept in an earthen pot become cool during summer?
Answer: Water seeps out through tiny pores and evaporates, extracting latent heat from the water inside, making it cooler.
Answer: Water seeps out through tiny pores and evaporates, extracting latent heat from the water inside, making it cooler.
11
Why does our palm feel cold when acetone, petrol, or perfume is put on it?
Answer: These liquids evaporate quickly, extracting latent heat from the skin, making it feel cold.
Answer: These liquids evaporate quickly, extracting latent heat from the skin, making it feel cold.
12
Why can we sip hot tea or milk faster from a saucer than from a cup?
Answer: The larger surface area of the saucer allows the liquid to cool down quickly due to faster evaporation.
Answer: The larger surface area of the saucer allows the liquid to cool down quickly due to faster evaporation.
13
What type of clothes should we wear in summer?
Answer: We should wear light-colored, cotton clothes as they reflect sunlight and help sweat evaporate quickly, keeping the body cool.
Answer: We should wear light-colored, cotton clothes as they reflect sunlight and help sweat evaporate quickly, keeping the body cool.
14
Convert the following temperatures to Celsius scale:
(a) 293 K = 19.85 °C
(b) 470 K = 196.85 °C
(a) 293 K = 19.85 °C
(b) 470 K = 196.85 °C
15
Convert the following temperatures to Kelvin scale:
(a) 25 °C = 298.15 K
(b) 373 °C = 646.15 K
(a) 25 °C = 298.15 K
(b) 373 °C = 646.15 K
16
Give reasons for the following observations:
(a) Naphthalene balls disappear with time.
Answer: Naphthalene undergoes sublimation, converting from solid to gas.
(b) We can get the smell of perfume several meters away.
Answer: Particles of perfume diffuse quickly due to their high kinetic energy.
(a) Naphthalene balls disappear with time.
Answer: Naphthalene undergoes sublimation, converting from solid to gas.
(b) We can get the smell of perfume several meters away.
Answer: Particles of perfume diffuse quickly due to their high kinetic energy.
17
Arrange the following substances in increasing order of forces of attraction between the particles — Water, Sugar, Oxygen.
Answer: Oxygen < Water < Sugar
Answer: Oxygen < Water < Sugar
18
What is the physical state of water at —
(a) 25 °C — Liquid
(b) 0 °C — Solid (Ice)
(c) 100 °C — Gas (Steam).
(a) 25 °C — Liquid
(b) 0 °C — Solid (Ice)
(c) 100 °C — Gas (Steam).
19
Give two reasons to justify:
(a) Water at room temperature is a liquid:
Answer: Its melting point is 0 °C and its boiling point is 100 °C, making it liquid at room temperature.
Particles have enough energy to move.
(b) An iron almirah is a solid at room temperature:
Answer: Particles have strong forces of attraction and its melting point is very high.
(a) Water at room temperature is a liquid:
Answer: Its melting point is 0 °C and its boiling point is 100 °C, making it liquid at room temperature.
Particles have enough energy to move.
(b) An iron almirah is a solid at room temperature:
Answer: Particles have strong forces of attraction and its melting point is very high.
20
Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer: Ice absorbs latent heat to melt, making it more effective for cooling.
Answer: Ice absorbs latent heat to melt, making it more effective for cooling.
21
What produces more severe burns, boiling water or steam?
Answer: Steam causes more severe burns because it contains latent heat, releasing more energy upon condensation.
Answer: Steam causes more severe burns because it contains latent heat, releasing more energy upon condensation.