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

NCERT Solutions for Class 7 Science Chapter 6 should be considered to find answers to all the tough questions related to Physical and Chemical Changes. CBSE Class 7 NCERT Solutions for Class 7 Chapter 6 explains the concept of change and its two fundamental kinds – physical change and chemical change. Further, this chapter is dedicated to explaining various examples of change. There are 12 exercises in this chapter and 4 extended-learning activities.  

The important topics of CBSE Class 7 Science Chapter 6 include crystallisation, galvanisation, rusting, chemical reactions, chemical change and physical change. Hardly anything beyond these topics will be asked in the CBSE exams. NCERT Solutions for Class 7 Science Chapter 6 – Physical and Chemical Changes is the perfect study material to strengthen your fundamentals related to this chapter. Meticulously prepared by the subject matter experts, this is a comprehensive and all-inclusive study material besides the NCERT textbook to help you grasp the solutions to the best.

Our science subject matter experts have prepared these NCERT solutions after extensive research on each topic of the chapter. These solutions provide you with the answers to all the questions available in the NCERT textbook. They will certainly help you to get on the right track while preparing for your exams.

Topics Covered in NCERT Solutions for Class 7 Science Chapter 6 –  Physical and Chemical Changes

CBSE NCERT Solutions Class 7 Science Chapter 6 – Physical and Chemical Changes is very vital to understand the various changes that occur in our everyday life. Changes are classified into two categories:
(i) Physical Change
(ii) Chemical Change.

Physical change refers to any change in the physical properties of a substance. The physical properties connote the shape, size, colour and the state of a substance. These changes are reversible in nature and in this type of change no new substance is formed.
For example: boiling of water, melting of ice, crushing of chalk, etc.

In Chemical change, one or more substances are formed. A chemical change generally involves chemical reactions and the results in the formation of new products. A chemical change is not a reversible process.
For example: rusting of iron, digestion of food, curdling of milk, etc.

Experiments Showing Change

  1. When Magnesium ribbon is burnt it forms oxides of Magnesium. This Magnesium oxide is a new substance.
    So, this is an example of Chemical change. Its equation is as follows:

Magnesium (Mg) + Oxygen (O2) Magnesium Oxide (MgO)

If Magnesium Oxide is added in water it results in the formation of a new substance which is Magnesium Hydroxide. The new substance is basic in nature and it will turn red litmus paper blue.

 Magnesium oxide (MgO) + Water (H2O) Magnesium Hydroxide (Mg(OH2))

  1. Another example of chemical change is the reaction between Copper Sulphate and Iron. The colour of Copper Sulphate solution changes from blue to green colour and a new substance, Iron Sulphate is formed. The iron which is put in this solution develops some brown deposits. This brown deposit is copper.
  2. When a pinch of baking soda is added to Vinegar, then carbon dioxide is released with a hissing sound. 

 Vinegar (Acetic acid) + Baking soda (Sodium bicarbonate) Carbon dioxide + other products.

This Carbon dioxide which is formed by the above reaction, when passed through lime water will produce Calcium Carbonate. And it will turn lime water milky.

 CO2 + Ca(OH) 2 (lime water) Calcium Carbonate (CaCO3) +H2O

  1. When iron objects are left open for some time, it forms a brownish layer due to the oxygen and moisture present in the atmosphere. This brownish layer is known as rust and the whole process of rust formation is called rusting.

 Iron (Fe) + Oxygen (O2) + Water (H2O) Rust (iron oxide Fe2O3)

The process to prevent rusting of iron is called Galvanization. In this process, a layer of zinc is deposited on the surface of iron objects. The water pipes of iron are galvanized. Crystallization refers to the process by which solids are obtained from their solutions. It is a kind of purification method. Crystallization is a physical change.

Exercise-Wise Discussion of NCERT Solutions for Class 7 Science Chapter 6 – Physical and Chemical Changes

  • This chapter contains exercises that will enable you to identify the various Physical and Chemical Changes.
  • In the Exercise, question 1 is about the classification of changes as physical and chemical involved in various processes.
  • Question 2 is of state true and false type. But you must go through the text in order to give the answer correctly.
  • Fill in the blanks are asked in question 3. 
  • Questions 4-6 are experimental based questions, they relate to the effect of the change on various materials.
  • Questions 7-10 are reasoning based. Your concepts should be very clear in order to give the right reasoning.
  • In the last two questions, you have to choose the correct option. 
  • NCERT Solutions for Class 7 Science Chapter 6 will be the best source from where you can easily revise the chapter in detail.

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