Physical and chemical changes class 7 | worksheet
Physical and chemical changes class 7. Download Physical and chemical changes class 7 worksheet based on the latest CBSE syllabus including MCQ on physical and chemical changes, long questions, define, questions on reaction, and more.
Points to remember.
Properties such as shape, size, colour and state of a substance are called its physical properties. A change in which a substance undergoes a change in its physical properties is called a physical change. A physical change is generally reversible. In such a change no new substance is formed.
A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction. Chemical changes are very important in our lives. All new substances are formed as a result of chemical changes. For example, digestion of food in our body, ripening of fruits, fermentation of grapes, etc
RUSTING OF IRON
The process of rusting can be represented by the following equation:
Iron (Fe) + Oxygen (O2, from the air) + water (H2O) ® rust (iron oxide Fe2O3)
This process of depositing a layer of zinc on iron is called galvanisation. The iron pipes we use in our homes to carry water are galvanised to prevent rusting.
Did you know Stainless steel is made by mixing iron with carbon and metals like chromium, nickel and manganese. It does not rust because of that mostely we use stainless steel in our household.