NCERT Solutions for Class 9 Science Chapter 1

NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings Page 3, Page 6, page 9, page 10 and Exercises question answers in English Medium or पेज 4 के उत्तर, पेज 6 के उत्तर, पेज 9 के उत्तर, पेज 11 के उत्तर and अभ्यास के प्रश्न उत्तर in Hindi Medium updated for new academic session 2020-21.

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NCERT Solutions for Class 9 Science Chapter 1

Class:9
Subject:Science – विज्ञान
Chapter 1:Matter in Our Surroundings

9th Science Chapter 1 Answers in English & Hindi Medium

NCERT Solutions for Class 9 Science Chapter 1 Matter in Our Surroundings all the in-text questions as well as chapter end exercises question’s answers are given below. Solutions are available in Hindi and English Medium to study online or download in PDF form free.






Why do substance undergo change in physical state?

Substance undergo change in physical state because both inter-particle spaces and inter-particle forces can be changed by changing the condition of temperature and pressure.

When sugar is dissolved in water, there is hardly an increase in volume. Which characteristic of matter is illustrated by this observation?

This is because of the presence of inter particle space or empty spaces. Particles or molecules of water can fill the empty space in the particles or molecules of sugar and vice versa. That is why there is hardly any change in the volume as a result of dissolution of sugar in water.

Define gaseous state of a substance.

A substance is said to be in the gaseous state if under normal pressure, its boiling point is below the room temperature.

How does pressure help in the liquefication of a gas?

Increase in pressure helps in the liquefication of a gas. The particles or molecules of a gas come closer and closer as the pressure is being increased gradually. They ultimately condense and as a result, the gas liquefies or changes into the liquid state.

Solids are generally very heavy while gases are light. Explain.

In the solids, the particle are very closely packed. As a result, the number of particles per unit volume is quite large. Therefore, the solids are normally quite heavy. In the gases, the particles are loosely packed. The number of particle per unit volume is completely small. Therefore, gases are light.



Questions for Practice on 9th Science Chapter 1

Question 1:
Solids are normally not compressible. Why can a sponge be readily pressed?
Answer 1:
A sponge made up of rubber has a large number of fine pores in which air remains filled. When the sponge is pressed, the air from the pores escapes and vacant space are left. Therefore, the sponge can be readily pressed on applying pressure.
Question 2:
Why do we sweat on a humid day?
Answer 2:
In humid day, the air around us has already high percentage of water vapours. Therefore, the water coming from the skin gets less opportunity to charge into vapours and remains sticking to our body. We therefore, swear more on a humidity day.
Question 3:
Kelvin scale of temperature is regarded as better than the Celsius scale. Give reason.
Answer 3:
In the Celsius scale of temperature we often come across a negative sign for the temperature (e.g., -8.5⁰C). Since the sign is always positive in the Kelvin scale, it is regarded as better.



Important Questions on 9th Science Chapter 1

Naphthalene balls disappear with time without leaving any solid. Why?
Naphthalene shows the property of sublimation. Evaporation of naphthalene takes place easily and so it disappears during course of time without leaving a solid.
निम्नलिखित प्रेक्षण के कारण बताएँ – गरमा-गरम खाने की गंध कई मीटर दूर से ही आपके पास पँहुच जाती है लेकिन ठंडे खाने की महक लेने के लिए आपको उसके पास जाना पड़ता है।
पदार्थ के कणों की गतिज ऊर्जा उनके तापक्रम बढ़ने पर बढ़ती है। गरम खाने के कणो में गतिज ऊर्जा अधिक होती है। अधिक गतिज ऊर्जा के कारण गरम खाने के कणों में विसरण अधिक होता है। इसी कारण गरम खाने की गंध कई मीटर दूर तक पहुँच जाती है जबकि ठंडे खाने की महक लेने के लिए हमे उनके पास तक जाना पढ़ता है।
We can get the smell of perfume sitting several meters away. Why?
Perfumes vaporize very fast and its vapours diffuse into air easily. That is why we can smell perfume sitting several meters away.
स्विमिंग पूल में गोताखोर पानी काट पाता है। इससे पदार्थ का कौन-सा गुण प्रेक्षित होता है?
जल के कणों के बीच दूरी अधिक होने के कारण आकर्षण बल कम होता है। इसलिए स्विमिंग पूल में गोताखोर पानी काट पाता है।
Water at room temperature is a liquid. Give reason.
Water at room temperature is a liquid because it has fluidity and has definite volume but no definite shape.
An iron almirah is a solid at room temperature. Give reason.
An iron almirah is a solid at room temperature because it is rigid and has a definite shape.
पदार्थ के कणों की क्या विशेषताएँ होती हैं?
पदार्थ के कणों की विशेषताएँ निम्नलिखित हैं:
पदार्थ के कणों के बीच रिक्त स्थान होता है।
पदार्थ के कण निरंतर गतिशील रहते है।
पदार्थ के कणों के बीच अंतरा-अणुक आकर्षण बल होता है।
Why is ice at 273 K more effective in cooling than water at the same temperature?
Ice at 273 K is less energetic than water. It is because of the difference in the latent heat of fusion which is present in water at the same temperature in the form of extra energy.
गैस पूरी तरह उस बर्तन को भर देती है, जिसमें इसे रखते हैं।कारण बताओ।
गैसों के अणुओं की गतिज ऊर्जा अधिकतम होती है तथा उनमे आकर्षण बल नगण्य होता है। इसलिए गैसों के अणु अत्यधिक तीव्र गति से सभी दिशाओ में गतिशील रहते है। इसी कारण उस धारक को पूरी तरह भर देते है जिसमे इसे रखा जाता है।
गैस बर्तन की दीवारों पर दबाव डालती है। कारण बताओ।
अत्यधिक गतिज ऊर्जा के कारण गैस के अणु बर्तन की दीवारों से टकराते रहते है इसी कारण दीवारों पर दबाव डालते है।
सामान्तया ठोस पदार्थों की की अपेक्षा द्रवों का घनत्व कम होता है। लेकिन आपने बर्फ के टुकड़े को जल में तैरते हुए देखा होगा। पता लगाइए, ऐसा क्यों होता है?
बर्फ का टुकड़ा ठोस होने के बावजूद उसमे हवा के बुलबुले अंदर कैद हो जाते है जिससे बर्फ का घनत्व जल के घनत्व से कम हो जाता है। जल से कम घनत्व होने के कारण ही बर्फ का टुकड़ा जल में तैरता है।
What produces more severe burns, boiling water or steam?
Steam produces more severe burns than boiling water. This is because steam has more energy than boiling water, present in it in the form of latent heat of vaporization.
किसी भी पदार्थ की अवस्था परिवर्तन के दौरान तापमान स्थिर क्यों रहता है?
पदार्थ की अवस्था परिवर्तन के दौरान दी गयी ऊष्मा (गुप्त ऊष्मा), पदार्थ के कणों की बीच आणुविक बन्धो को तोड़ने में खर्च होती है। इसीलिए अवस्था परिवर्तन के दौरान दी गयी ऊष्मा पदार्थ का तापमान नहीं बढ़ा पाती।

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