CBSE NCERT Solutions for Class 7 Science Chapter 6

CBSE NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes or अध्याय 6 भौतिक एवं रासायनिक परिवर्तन in हिंदी मीडियम free to download in English Medium PDF or View online or View in Video Format on latest Text Books for the academic session 2019 – 2020. Share Your View with your friends and Download Class 7 Offline Apps for offline use.


Class:7
Subject:Science – विज्ञान
Chapter 6:Physical and Chemical Changes

Table of Contents

CBSE NCERT Solutions for Class 7 Science Chapter 6

Physical and Chemical Changes: Question – Answers

7 Science Chapter 6: Physical and Chemical Changes

CBSE NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes is given below to use online or View in Video Format . Download links are given at the Top of the page. Visit to हिंदी मीडियम or Class 7 Science main page. Download Class 7 Science App for offline use.

CBSE NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes




CBSE NCERT Solutions for Class 7 Science Chapter 6 in PDF free
7 Science chapter 6 answers guide

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7 विज्ञान अध्याय 6 अभ्यास के प्रश्न उत्तर

NCERT Solutions for Class 7 Science अध्याय 6: भौतिक एवं रासायनिक परिवर्तन in हिंदी मीडियम is given below. Visit to English Medium or  Class 7 Science main page.

NCERT Solutions for Class 7 Science अध्याय 6: भौतिक एवं रासायनिक परिवर्तन
7th science chapter 6 solutions




7 science answers ch. 6
chapter 6 science class 7

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7 Science Chapter 6 Sols in Video

NCERT Solutions for class 7 Science Chapter 6 explanation with question answers in video format with complete description. Download 7 Science App for offline use.

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Important Questions with Answers
  1. Which of the following is a physical change?
    (a) Rusting of iron
    (b) Combustion of magnesium ribbon
    (c) Burning of candle
    (d) Melting of wax
  2. Two drops of dilute sulphuric acid were added to 1 g of copper sulphate powder and then small amount of hot water was added to dissolve it (step I). On cooling, beautiful blue coloured crystals got separated (step II). Step I and step II are:
    (a) physical and chemical changes respectively.
    (b) chemical and physical changes respectively.
    (c) both physical change.
    (d) both chemical change.
  3. Which of the following is a chemical change?
    (a) Twinkling of stars
    (b) Cooking of vegetables
    (c) Cutting of fruits
    (d) Boiling of water
  4. Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
    (a) It is more than 7 metres high.
    (b) It weighs about 6000 kg.
    (c) It was built more than 1600 years ago.
    (d) It has not rusted after such a long period.
  5. A chemical change may involve –
    (a) change in colour only
    (b) change in temperature only
    (c) evolution of gas only
    (d) any or all of the above
  6. Galvanisation is a process used to prevent the rusting of which of the following?
    (a) Iron
    (b) Zinc
    (c) Aluminium
    (d) Copper
  7. Which of the following is/are true when milk changes into curd?
    (i) Its state is changed from liquid to semi solid.
    (ii) It changes colour.
    (iii) It changes taste.
    (iv) The change cannot be reversed.
    Choose the correct option from below:
    (a) (i) and (ii) are correct
    (b) (ii) and (iii) are correct
    (c) (i), (iii) and (iv) are correct
    (d) (i) to (iv) are correct
  8. Paheli’s mother made a concentrated sugar syrup by dissolving sugar in hot water. On cooling, crystals of sugar got separated. This indicates a –
    (a) physical change that can be reversed.
    (b) chemical change that can be reversed.
    (c) physical change that cannot be reversed.
    (d) chemical change that cannot be reversed.
  9. A man painted his main gate made up of iron, to
    (i) prevent it from rusting. (ii) protect it from sun. (iii) make it look beautiful. (iv) make it dust free.
    Which of the above statement(s) is/are correct?
    (a) (i) and (ii)
    (b) (ii) and (iii)
    (c) only (ii)
    (d) (i) and (iii)
  10. Which of the following statement is incorrect for a chemical reaction?
    (a) Heat may be given out but never absorbed.
    (b) Sound may be produced.
    (c) A colour change may take place.
    (d) A gas may be evolved.



Answers

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रिक्त स्थान को भरिए – खाने के सोडे का रासायनिक नाम ___________________ है।

खाने के सोडे का रासायनिक नाम सोडियम बाइकार्बोनेट या सोडियम हाइड्रोजन कार्बोनेट (NaHCO3) है।

When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling.
Chemical Changes: The wax near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapour, heat and light.
Cooking of food, is another example where both physical and chemical changes occurs.

आप यह कैसे दिखाएँगे कि दही का जमना एक रासायनिक परिवर्तन है।

दही का जमना एक रासायनिक परिवर्तन है क्योंकि इसमें एक नया पदार्थ (लैक्टिक अम्ल) बनता है जो मूल पदार्थ (वसा और प्रोटीन) यानी दूध से स्वाद में भिन्न होता है। इसके अलावा परिवर्तन अपरिवर्तनीय है (दही को दूध में परिवर्तित नहीं किया जा सकता है)।

समझाइए कि लकड़ी के जलने और उसे छोटे टुकड़ों में काटने को दो भिन्न प्रकार के परिवर्तन क्यों माना जाता है।

लकड़ी जलाना एक रासायनिक परिवर्तन है क्योंकि जलने पर लकड़ी राख (कार्बन), कार्बन डाइऑक्साइड गैस, जल वाष्प, गर्मी और प्रकाश जैसे नए पदार्थों में परिवर्तित हो जाती है। इसके अलावा परिवर्तन अपरिवर्तनीय है।
जबकि छोटे टुकड़ों में लकड़ी काटना एक भौतिक परिवर्तन है क्योंकि लकड़ी की मूल संरचना नहीं बदलती है। कोई नया पदार्थ नहीं बनता है।

कॉपर सल्फेट के क्रिस्टल कैसे बनते हैं, इनका वर्णन कीजिए।

कॉपर सल्फेट के क्रिस्टल निम्नानुसार तैयार किए जाते हैं:
एक बीकर में पानी ले लो और सल्फ्यूरिक अम्ल की कुछ बूँदें डालें।
पानी गर्म करें। जब यह उबलने लगे तो इसमें लगातार कॉपर सल्फेट पाउडर डालें।
संतृप्ति स्तर तक कॉपर सल्फेट पाउडर डालना जारी रखें।
घोल को छान लें और ठंडा होने के लिए छोड़ दें।
हम कुछ घंटों के बाद कॉपर सल्फेट के क्रिस्टल का निरीक्षण कर सकते हैं।

Explain how painting of an iron gate prevents it from rusting.

For rusting, the presence of both oxygen and water (or water vapour) is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting.

Explain why rusting of iron objects is faster in coastal areas than in deserts.

For rusting, the presence of both oxygen and moisture (water vapour) is required. In coastal areas the quantity of moisture content in air is high (highly humid) as compared to desert regions (low humid), so the rusting becomes faster in coastal areas.