Physical Change and Chemical Change- Rusting

Physical Change

Properties such as shape, size, state of the substance and its colour are known as physical properties. Physical properties are affected by the physical change.

Physical Change

Physical Change

For Example, when ice changes to water, there is a change in the physical state of ice, i.e. it changes from solid to liquid. If we cool the water again, ice will be formed making it a reversible reaction. Also, no new substance is formed in the above physical change.

physical change

Chemical Change

A change in which one or more new substances are formed is known as chemical change.

Chemical change

For Example, when the iron is exposed to air and moisture, rust formation takes place. Rust is nothing but Iron Oxide; a new substance formed out of the reaction. The colour of the surface of the iron also changes. Hence, rusting of iron is a chemical change.

Physical Change

Rusting boats on the bank of river

Rusting of Iron

When substances made of iron are exposed to oxygen and moisture (water), rusting takes place. Rusting removes a layer of material from the surface and makes the substance weak. Rusting is a chemical change.

Chemical reaction taking place during rusting is shown below.

Rusting Reaction

Rusting is undesirable and methods are used to avoid rusting.

Rusting

The process of depositing zinc on the iron to prevent rusting is known as galvanisation. A striking example of the use of galvanisation is the water pipes used in houses.

Crystallization

A physical process of obtaining large crystals of a pure substance from its solution is known as crystallization. Crystallization is a physical change.

Crystallization

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