Physical change and chemical change.

About physical and chemical change

Physical change

It is a temporary change where there is no formation of new substance and which can be reversed back to its original shape.

 

    Characteristics of physical change:

1. The change is temporary and reversible
2. No new substance is formed
3. Amount of energy required to bring about a physical change is generally equal to the energy released when the change is reversed
4. There is no change in mass of substance

Chemical change.

It is a permanent change where there is formation of new substance and that cannot be reversed back to its original shape.

Characteristics of physical change:

1. A chemical change is permanent and irreversible
2. One or more new substance is formed
3. The mass of substance undergoing a chemical change is generally altered
4. Energy change is generally involved in a chemical change

Difference between physical and chemical change

Physical change	Chemical change
No new substance formed	One or more new substance is formed
Can be reversed back to its original shape	Cannot be reversed back
No energy change or small energy change is involved	Energy change is involved
It is temporary change	It is permanent change
There is no change in mass	There is change in mass

 

ammonium chloride ammonia + hydrogen chloride

The equation shows that ammonium chloride (a white solid) can break down to form ammonia and hydrogen chloride. It also shows that ammonia and hydrogen chloride (colourless gases) can react to form ammonium chloride again.

The animation below shows a reversible reaction involving white anhydrous copper(II) sulfate and blue hydrated copper(II) sulfate, the equation for which is:

anhydrous copper(II) sulfate + water hydrated copper(II) sulfate