STD VIII – PHYSICAL AND CHEMICAL CHANGES (Online)

Introduction

This theme will enable children to understand that there are different types of changes

in our surroundings which as slow/fast, reversible/irreversible, periodic/non-periodic and physical/chemical. In physical changes, no new substance is formed while in chemical change, a new substance with properties different from the element forming that substance is formed. Learning of these changes will also help in developing different scientific skills amongst them.

Physical Change

There is no addition or deduction of energy during the physical change, but the energy required for completion of change is released when the change is reversed.

Chemical Change

Energy like light, pressure, heat energy is required for chemical changes. Such energy is generally absorbed or released during the chemical change.

Examples of Physical changes:

Dissolving salt/sugar in water.

Sublimation of iodine.

Switching on an electric bulb.

Melting of solid/change in state of water.

Drying of wet clothes.

Examples of chemical changes

Burning of paper.

Burning of Magnesium in oxygen.

Cooking food.

Boiling/curdling milk.

Rusting of iron.