Physical And Chemical Changes
Physical and chemical changes:
All substances around us undergo changes. In some cases, the changes are small and difficult to defect. In other cases, the changes are obvious and easy to defect. These changes generally get accerelated if we heat the substances.
Most of these changes can be classified under two headings.
a) Physical change b) Chemical Change
What are Physical Changes?
A physical change is one where there are changes only in the physical properties of the components. For example, when a pure gold ingot is melted, then it changes from solid gold to liquid gold. However, there is no change in the chemical composition of the component, which is gold, in case of physical changes.
In the example of the gold ingot, the observed changes are listed below:
1. The solid gold ingot changes to liquid form. Cooling it back will help the gold retain its solid form again, though there be changes in its shape.
2. The temperature of the liquid gold is quite high, and it can be reversed back to its original temperature by cooling it.
3. The shape of the solid ingot changes when it is liquified. Using proper methods of shaping and casting while cooling the liquid gold can help get back the original shape.
These are all changes in the physical properties of the material and no chemical change takes place.
Definition of Physical Change: A physical change is one that changes the shape ,size,physical state,and appearance of a substance, but not its chemical composition