Matter In Our Surroundings Class 9 Important Questions With Answers

CBSE Class 9 Science Chapter 1 – Matter in Our Surroundings introduces students to the fundamental concept of matter and its different states. This chapter explains the properties and behavior of matter in everyday life and builds a strong base for advanced science topics in higher classes.

To prepare effectively, practicing Class 9 Science Important Questions is highly recommended. Regular practice not only boosts confidence but also makes scoring well in exams easier. With the right support and study materials from Infinity Learn, you can master this chapter smoothly and strengthen your understanding.

CBSE Important Questions Class 9 Science Chapter 1 PDF

The PDF link for CBSE Class 9 Science Chapter 1 – Matter in Our Surroundings Important Questions is provided below. By downloading and using this PDF, students can revise key concepts and practice important questions, helping them prepare thoroughly for exams. Make the most of this resource to strengthen your understanding of matter and its properties.

Matter In Our Surroundings Class 9 Questions Answers

Below we have provided CBSE Important Questions Class 9 Science Chapter 1 Matter in Our Surroundings-

Q1. Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

Ans: Almonds, air, chair, smell of perfume, cold drink, and smell are matter.

Q2. Convert the following temperatures to Celsius scale:

(a) 300 K

(b) 573 K

Ans:

(a) 300 K = 27 °C

(b) 573 K = 300 °C

Q3. What will be the state of water at:

(a) 250 °C

(b) 100 °C

Ans:

(a) At 250 °C → Gaseous state

(b) At 100 °C → Gaseous state

Q4. Why does the temperature of a substance remain constant during the change of state?

Ans: Because the heat supplied is used to overcome the forces of attraction between particles, not to raise temperature.

Q5. How can atmospheric gases be liquefied?

Ans: By lowering temperature and increasing pressure.

Also Check:

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Q6. Arrange the following substances in increasing order of force of attraction: Water, Sugar, Oxygen.

Ans: Oxygen < Water < Sugar.

Q7. What will be the physical state of water at:

(a) 25 °C

(b) 0 °C

(c) 100 °C

Ans:

(a) At 25 °C → Liquid

(b) At 0 °C → Solid

(c) At 100 °C → Gas

Q8. Why does the rate of evaporation decrease with increase in humidity?

Ans: Because the air already contains a large amount of water vapour, so evaporation slows down.

Q9. Differentiate between boiling and evaporation.

Ans:

• Boiling → A bulk phenomenon; occurs throughout the liquid at a fixed temperature.
• Evaporation → A surface phenomenon; occurs only at the surface and at all temperatures.

Q10. What happens to the rate of evaporation when the temperature is increased?

Ans: The rate of evaporation increases.

Q11. Which state of matter has the least interparticle spacing?

Ans: Solids have the least interparticle spacing.

Q12. What will happen to the rate of evaporation if surface area is decreased and temperature is increased simultaneously?

Ans: The rate of evaporation will remain the same.

Q13. Convert 300 K into Celsius.

Ans:

300 K = 300 – 273 = 27 °C.

Q14. Name the processes:

(a) Liquid → Gas

(b) Gas → Liquid

Ans:

(a) Vaporization

(b) Condensation

Q15. What are the three states in which water exists?

Ans: Water exists as a liquid, solid, and gas.

Q16. Why does hot food spread smell faster than cold food?

Ans: In hot food, particles move faster and spread quickly; in cold food, particles move slowly.

Q17. Arrange in increasing order of density: Air, Honey, Exhaust from chimneys, Chalk, Cotton, Water, Iron.

Ans: Air < Exhaust gases < Cotton < Water < Honey < Chalk < Iron.

Q18. Why does ice float on water?

Ans: Because the structure of ice has empty spaces, making its density lower than that of water.

Q19. Why does a desert cooler work better on hot, dry days?

Ans: Because high temperature and low humidity increase evaporation, making cooling more effective.

Q20. Why does water kept in an earthen pot become cool during summer?

Ans: Water seeps out through the tiny pores of the pot and evaporates, taking away heat and cooling the water.

Short Answer Questions (2 Marks)

1. The mass per unit volume of a substance is called density. (density = mass/volume).

Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton, and iron.

Ans. The substances arranged in the correct order of increasing density are: Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron.

2. Give reasons for the following observation:

The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.

Ans. At higher temperatures, the diffusion rate of particles increases compared to lower temperatures. Since hot sizzling food has a higher temperature than cold food, its aroma spreads faster and can be sensed from several meters away.

3. Why does a desert cooler cool better on a hot dry day?

Ans. In a desert cooler, hot air passes through the straw mats and causes water to evaporate rapidly. Since evaporation is faster on a hot, dry day, the air cools more effectively.

4. Liquids generally have a lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

Ans. Ice floats on water because its 3D structure contains large empty spaces, making it less dense than liquid water, which allows it to float.

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

Ans. Perfume and petrol are volatile liquids. When placed on the palm, they evaporate quickly, absorbing heat from the skin and producing a cooling effect.

6. How does the water kept in an earthen pot (matka) become cool during summer?

Ans. In an earthen pot, water seeps out through tiny pores and evaporates, producing a cooling effect. Hence, water stored in such pots stays cool during summer.

Q7. Why are we able to sip hot tea or milk faster from a saucer than from a cup?

Ans: A saucer has a larger surface area than a cup, which increases the rate of evaporation. This makes the tea or milk cool faster, allowing us to sip it easily.

Q8. What type of clothes should we wear in summer?

Ans: We should wear cotton clothes in summer. Cotton absorbs sweat and allows it to evaporate easily, and since evaporation causes cooling, cotton keeps us comfortable.

Q9. Convert the following temperatures to Celsius scale.

(a) 293 K

Ans: °C = K – 273 = 293 – 273 = 20 °C

(b) 470 K

Ans: °C = K – 273 = 470 – 273 = 197 °C

Q10. Convert the following temperatures to Kelvin scale.

(a) 25 °C

Ans: K = °C + 273 = 25 + 273 = 298 K

(b) 373 °C

Ans: K = °C + 273 = 373 + 273 = 646 K

Q11. Give reasons for the following observations:

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

Ans: Naphthalene undergoes sublimation, changing directly from solid to gas without passing through the liquid state.

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

Ans: Perfumes are volatile substances. They quickly convert from liquid to gas and diffuse with air particles, allowing the smell to reach us from a distance.

More resources for class 9

• NCERT Solutions for Class 9 Maths
• NCERT Solutions for Class 9 English
• NCERT Solutions for Class 9 Social Science
• NCERT Solutions for Class 9 Science

Q12. Justify the following:

(a) Water at room temperature is a liquid.

Ans: Room temperature lies between 0 °C and 100 °C, the range in which water exists in liquid state. Hence, water at room temperature is a liquid.

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

Ans: The melting point of iron is very high compared to room temperature. Therefore, an iron almirah remains solid at room temperature.

Q13. Why is ice at 273 K more effective in cooling than water at the same temperature?

Ans: At 273 K, ice absorbs latent heat of fusion from the surroundings while melting into water. This additional heat absorption makes ice more effective in cooling than water at the same temperature.

Q14. What produces more severe burns: boiling water or steam?

Ans: Steam causes more severe burns because when it condenses into water, it releases latent heat in addition to the heat already present.

Q15. What is evaporation? What factors affect it?

Ans: Evaporation is the process of conversion of a liquid into vapour at a temperature below its boiling point.

Factors affecting evaporation:

1. Surface area
2. Temperature
3. Humidity
4. Wind speed

Q16. What happens when we apply pressure to the particles of matter?

Ans: Applying pressure brings the particles closer together, reducing the space between them.

Q17. Define latent heat of vaporization and latent heat of fusion.

Ans:

• Latent heat of vaporization: Heat energy required to change 1 kg of a liquid into vapour at atmospheric pressure without changing temperature.
• Latent heat of fusion: Heat energy required to change 1 kg of a solid into liquid at atmospheric pressure without changing temperature.

Q18. If the melting point of object A is high, what state will it be at room temperature?

Ans: Since room temperature is much lower than its high melting point, object A will exist in the solid state at room temperature.

Q19. What happens when the temperature of a solid increases?

Ans: On heating, the particles of the solid gain energy, their kinetic energy increases, and they vibrate more vigorously. Once they overcome the forces of attraction, they begin to move freely, leading to a change of state.

Q20. When heat is supplied to a solid, what does the heat energy do to its particles?

Ans: The heat energy increases the kinetic energy of the particles, helping them overcome the forces of attraction and change from solid to liquid.

Long Answer Questions (3 Marks)

Q1. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Ans: This shows that water particles are held together by weak forces of attraction. When an external force is applied, these particles can be separated, allowing the diver to cut through water.

Q2. What are the characteristics of the particles of matter?

Ans:

• Particles of matter are in continuous motion.
• There are spaces between the particles of matter.
• Particles of matter attract each other with a certain force.

Q3 (a). Tabulate the differences in the characteristics of states of matter.

Ans:

Q3 (b). Comment on the following:

• Rigidity: Ability of matter to maintain its shape when external force is applied. Present in solids.
• Compressibility: Ability of matter to reduce volume under high pressure. Seen in liquids (slightly) and gases (highly).
• Fluidity: Ability of matter to flow and change shape. Present in liquids and gases.
• Filling a gas container: Gases are highly compressible and fluid, so they completely fill a container. Large amounts can be stored in small volumes.
• Shape: Solids have definite shapes; liquids take the shape of their container; gases have no fixed shape.
• Kinetic energy: All particles have kinetic energy. Solids < Liquids < Gases.
• Density: Defined as mass per unit volume (Density = Mass/Volume). Solids usually have the highest density, gases the least.

Q4. Give reasons:

(a) A gas fills completely the vessel in which it is kept.

Ans: Gas particles have negligible forces of attraction and move freely in all directions, thus filling the container completely.

(b) A gas exerts pressure on the walls of the container.

Ans: Gas particles move freely and collide continuously with the container walls. These collisions exert pressure.

(c) A wooden table should be called a solid.

Ans: A wooden table has rigid particles, definite shape, and clear boundaries, so it is a solid.

(d) We can easily move our hand in the air but to do the same through a solid block of wood we need a karate expert.

Ans: Air is a gas with very weak forces of attraction, so particles can be easily displaced. In solids, particles have strong forces of attraction, requiring large external force to separate them, hence the need for great strength.

Benefits of Class 9 Science Chapter 1 Matter in Our Surroundings Important Questions

Students struggling with Class 9 Science Chapter 1 are advised to practice the important questions for better preparation. These questions offer several benefits:

• They are designed strictly as per the CBSE Class 9 syllabus and exam format, ensuring students don’t lose marks due to off-syllabus practice.
• The questions are carefully chosen by experienced teachers, keeping in mind the learning level and intellectual capacity of students.
• Many of these questions are highly probable to appear in exams, helping students prepare more effectively and with confidence.
• Each question is provided with detailed, step-by-step solutions, making concepts easier to understand and revise.