Looking for accurate SEBA Class 9 Science Chapter 1 (Matter in Our Surroundings) textual solutions for the 2026–27 academic year? Access complete step-by-step textbook exercise answers covering physical nature of matter, states of matter (solid, liquid, gas), interconversion of states, latent heat, and factors affecting evaporation to score top marks in your exams.
Blue question
1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Ans.
Matter has mass and occupies space.
Matter: Chair, air, smell, almonds, cold, lemon water, smell of perfume
Not matter: Love, hate, thought
2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.
Ans.
Particles of matter move faster when they are hot.
Hot food releases smell (vapour) particles quickly and they diffuse fast in air.
Cold food releases smell slowly, so you must go closer to smell it.
3. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Ans.
It shows that particles of matter have spaces between them.
The diver can move through water because water particles are not tightly packed.
4. What are the characteristics of the particles of matter?
Ans.
- They have space between them.
- They are continuously moving.
- They attract each other.
- They are very small in size.
5. Convert the following temperatures to Celsius scale:
a. 300 K
b. 573 K
Ans.
Formula: °C = K – 273
a. 300 K = 300 – 273 = 27°C
b. 573 K = 573 – 273 = 300°C
SEBA Class 9 Science Chapter 1 Solutions
6. What is the physical state of water at:
a. 250°C
b. 100°C?
Ans.
a. At 250°C, water exists as steam (gas).
b. At 100°C, water exists as both liquid and gas because it is at the boiling point and starts changing into steam.
7. For any substance, why does the temperature remain constant during a change of state?
Ans.
During a change of state (like melting or boiling), the heat energy supplied is used to break the forces of attraction between particles. This energy is called latent heat.
Therefore, the temperature does not rise until the entire substance changes its state.
8. Suggest a method to liquefy atmospheric gases.
Ans.
Atmospheric gases can be liquefied by:
- Increasing pressure
- Lowering temperature
This brings gas particles closer together and changes them into a liquid.
9. Why does a desert cooler cool better on a hot dry day?
Ans.
On a hot and dry day, the air has low humidity, so water evaporates faster. During evaporation, heat is absorbed from the surroundings, which causes cooling. Faster evaporation leads to more cooling, so the desert cooler works better.
10. How does the water kept in an earthen pot (matka) become cool during summer?
Ans.
An earthen pot has tiny pores through which a small amount of water seeps out. This water evaporates from the surface, and during evaporation, it absorbs heat from the pot and the water inside. As a result, the water in the pot becomes cool.
Class 9 Science Chapter 1 Question Answer SEBA 2026-27
11. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Ans.
Acetone, petrol, and perfume evaporate very quickly. During evaporation, they absorb heat from our palm, which makes the palm feel cold.
12. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Ans.
In a saucer, the hot tea or milk spreads out and gets a larger surface area. This increases the rate of evaporation, causing it to cool faster. Therefore, we can sip it sooner than from a cup without burning our mouth.
13. What type of clothes should we wear in summer?
Ans.
In summer, we should wear light-coloured, cotton clothes. Cotton absorbs sweat and allows it to evaporate, which cools the body, while light colours reflect heat. Loose-fitting clothes are also better, as they allow air to circulate and help the body stay cool.
Matter in Our Surroundings Class 9 SEBA Textual Exercise Solutions
Textbook question
1. Convert the following temperatures to the Celsius scale.
(a) 293 K
(b) 470 K
Ans.
Formula: °C = K – 273
(a) 293 K = 293 – 273 = 20°C
(b) 470 K = 470 – 273 = 197°C
2. Convert the following temperatures to the Kelvin scale.
(a) 25°C
(b) 373°C
Ans.
Formula: K = °C + 273
(a) 25°C = 25 + 273 = 298 K
(b) 373°C = 373 + 273 = 646 K
3. Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving any solid.
Ans.
Naphthalene balls change directly from solid to gas without becoming liquid. This process is called sublimation. As a result, they slowly vanish into the air without leaving any solid behind.
(b) We can get the smell of perfume sitting several metres away.
Ans.
Perfume particles mix with air and spread quickly due to diffusion. This spreading of particles allows the smell to reach our nose even from a distance.
SEBA Class 9 Science Chapter 1 Textbook Answers
4. Arrange the following substances in increasing order of forces of attraction between the particles – water, sugar, oxygen.
Ans.
Oxygen < Water < Sugar
(Weakest attraction -> Strongest attraction)
5. What is 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 -> Both solid and liquid (melting point)
(c) At 100°C -> Both liquid and gas (boiling point)
6. Give two reasons to justify –
(a) Water at room temperature is a liquid.
Ans.
- It has a definite volume but no definite shape.
- Its particles are less tightly packed and can flow easily.
(b) An iron almirah is a solid at room temperature.
Ans.
- It has a definite shape and fixed volume, which makes it rigid.
- Its melting point (about 1538°C) is much higher than room temperature.
7. Why is ice at 273 K more effective in cooling than water at the same temperature?
Ans.
Ice at 273 K absorbs extra heat energy (called latent heat of fusion) from the surroundings to change from solid to liquid. Because it absorbs this extra heat, ice cools things more effectively than water at the same temperature.
Class 9 Science Chapter 1 Matter Solutions
8. What produces more severe burns, boiling water or steam?
Ans.
Steam produces more severe burns than boiling water because it contains extra energy called latent heat of vaporisation. When steam touches the skin and condenses into water, it releases this extra heat, causing greater damage.
9. Name A, B, C, D, E and F in the process showing change of state:
Solid -> Liquid -> Gas -> Solid
Ans.
- A: Melting / Fusion (Solid to Liquid)
- B: Vaporisation / Boiling (Liquid to Gas)
- C: Sublimation (Solid to Gas)
- D: Condensation (Gas to Liquid)
- E: Deposition (Gas to Solid)
- F: Freezing / Solidification (Liquid to Solid)
🔬 Updated Solutions Notice: This page features complete, step-by-step SEBA Class 9 Science Chapter 1 (Matter in Our Surroundings) Textual Exercise Solutions updated for the 2026–27 academic session. All physical chemistry concepts, unit conversion calculations (Kelvin to Celsius), and scientific explanations strictly follow the latest revised Assam Board (SEBA) curriculum.
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