What are changes?

Changes are taking place in the world around us all the time. Sometimes, after a change, things can be put back to the way they were before. Other types of change leave things altered forever.

Reversible change

Reversible changes are easy to reverse, or undo. For example, ice can melt to become water, and then freeze, turning back into ice again. A frozen lolly is solid. It is made of ice. If you take the ice lolly out of the freezer, it gets warm and the ice begins to melt. After a while, all of the ice has melted and has become a liquid. The liquid can be poured into a lolly mould and then put into a freezer. As the liquid gets cold it freezes and turns into ice.

Irreversible change

Irreversible changes cannot be undone. They are permanent. For example, once you have cooked an egg, it cannot be turned back into a raw one! The white of a raw egg is a clear, runny liquid. Heating the egg causes a change that cannot be undone. The egg white has now become a white solid. It cannot be turned back into a clear liquid.

Everyday changes

Here are some examples of common reversible and irreversible changes that you may see from time to time.

Steamed window

When invisible water vapour in the air hits a cold window, it condenses, turning into tiny water droplets. When the window gets warm, the droplets turn back into water vapour.

Autumn leaves

Most trees lose their leaves in autumn. Before the leaves fall off the tree, they charge from green to red to brown. This change cannot be undone, which means it is permanent.

Rusting

Rust forms slowly when iron comes into contact with air and water. Iron objects left in the rain become flaky and reddish-brown forever.

Rotting food

When food gets old, it can be attacked by tiny living things called mould and bacteria. As the food rots it turns brown, smells nasty, and shrivels up. It cannot be changed back into its fresh form again.

 

Picture Credit : Google