NCERT Solutions for Class 7 Science Chapter 6

Physical and Chemical Changes Class 7

Chapter 6 Physical and Chemical Changes Exercise Solutions

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Exercise : Solutions of Questions on Page Number : 65

Q1 :  

Classify the changes involved in the following processes as physical or chemical changes:

(a) Photosynthesis

(b) Dissolving sugar in water

(c) Burning of coal

(d) Melting of wax

(e) Beating aluminium to make aluminium foil

(f) Digestion of food


Answer :

(a) Photosynthesis Chemical change

(b) Dissolving sugar in water Physical change

(c) Burning of coal Chemical change

(d) Melting of wax Physical change

(e) Beating aluminium to make aluminium foil Physical change

(f) Digestion of food Chemical change

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Q2 :  

State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

(a) Cutting a log of wood into pieces is a chemical change. (True/False)

(b) Formation of manure from leaves is a physical change.

(True/ False)

(c) Iron pipes coated with zinc do not get rusted easily. (True/False)

(d) Iron and rust are the same substances. (True/False)

(e) Condensation of steam is not a chemical change. (True/False)


Answer :

(a) False

Cutting a log of wood into pieces is a physical change.

(b) False

Formation of manure from leaves is a chemical change.

(c) True

(d) False

Iron and rust are different substances. Rust is iron oxide

(e) True

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Q3 :  

Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.

(b) The chemical name of baking soda is _________.

(c) Two methods by which rusting of iron can be prevented are _________and

____ ____.

(d) Changes in which only _____ __ properties of a substance change are called physical changes.

(e) Changes in which new substances are formed are called _________changes.


Answer :

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Q4 :  

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.


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Q5 :  

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.


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Q6 :  

How would you show that setting of curd is a chemical change?


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Q7 :  

Explain why burning of wood and cutting it into small piece are considered as two different types of changes.


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Q8 :  

Describe how crystals of copper sulphate are prepared.


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Q9 :  

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


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Q10 :  

Anaerobic bacteria digest animal waste and produce biogas (Change - A).

The biogas is then burnt as fuel (Change - B). The following statements pertain to these changes. Choose the correct one.

(i) Process - A is a chemical change.

(ii) Process - B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.


Answer :

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<< Previous Chapter 5 : Acids, Bases and Salts Next Chapter 7 : Weather, Climate and Adaptations of Animals to Climate >>

Science : CBSE NCERT Exercise Solutions for Class 7th for Physical and Chemical Changes will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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