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Class 7
Chapter 6 Class 7 - Physical and Chemical Changes

When one or more properties of a substance become different we say change has taken place in it. 

Changes in everyday life are:

  • Formation of curd from milk
  • Cooking of food
  • Ripening of fruit
  • Rusting of Iron

There are two types of changes:

  • Physical Changes
  • Chemical Changes

Physical change 

Chemical change

  1. Changes in properties such as size, shape, colour and state of a substance are called physical changes.
  2. No new substance is formed. 
  3. A physical change is a temporary change. It can be reversed .
  4. Very little energy is either absorbed or evolved in a physical change.
  5. A temporary change in colour may take place in a physical change.
  1. A change in which one or more new substances are formed is called a chemical change 
  2. One or more new substances are formed. 
  3. A chemical change is permanent. It is irreversible .
  4. A lot of energy (in the form of heat light) is either absorbed or given out in a chemical change.
  5. A permanent change in colour may take place in chemical change.

All of these statements have exceptions to them. We will learn about these as we study the topics in detail.

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CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo