A reversible change is a chemical change where no new materials are created, and the original material can be recovered. Examples include freezing water to make ice or melting chocolate.
What’s the difference between a reversible change and an irreversible change?
The essential difference between a reversible change and an irreversible one lies in whether the chemical properties involved change – in a reversible one, they stay the same, whereas, in an irreversible one, they change.
Typically, if a material physically changes, it is reversible, whereas if it changes chemically, it is not.
It can be hard to tell the difference between a physical change and a chemical one sometimes – when boiling water to turn it into water vapor, it certainly looks like the water has become something else entirely. However, if you zoom in closer, you can see what’s happening.
Using the example of water, if you had the technology to zoom in on a block of ice small enough to see the particles, you’d be able to see that water particles are made up of two elements, Hydrogen, and Oxygen. Tiny particles of Hydrogen and Oxygen called atoms are bonded together in water to form a particular type of particle called a molecule, which occurs when two or more elements become bonded together to form larger particles. It makes water a compound, like many other earth materials.
When we heat ice to melt it into the water, the bonds between the water particles are weakened and change, allowing the ice to go from a solid to a liquid. However, the bonds between the atoms inside the water molecules don’t break, so the particles don’t change. It means that whatever state the water is in, whether it’s ice, water, or water vapor, it’s still water, and the change can be reversed.
In an irreversible change, it works a bit differently. For example, suppose you mix vinegar and bicarbonate of soda to make a model volcanic eruption. When these two chemicals are combined, the particles they’re made up of break down and recombine to make completely different materials. After the change has occurred, you can’t turn the bubbles of gas and the liquid left behind back into vinegar and bicarbonate of soda because the mixture of particles left behind by the reaction has changed.
Why are reversible changes essential to learn about?
As with all chemical reactions, reversible changes help to explain some of the things we see happening in the world around us.
Every time children melt, freeze, or (in later life) boil something, they will be able to recognize to some degree what processes are allowing it to happen.
As well as developing their scientific knowledge, it is also fascinating to learn about.
