A material can undergo either a chemical change, physical change, or both.
The key differences between chemical and physical change are seen in terms of visible variation in forms.
In a physical change, there is always an alteration in the appearance of matter which can be perceived by any of our five senses.
While in a chemical change the physical appearance may or may not vary.
The Physical change can be seen by a modification in color, state of matter (transition from solid liquid or gas), temperature, or texture.
An example of physical change is the conversion of ice into water.
Here you can notice the physical alteration occurs in terms of a difference in colors i.e. white to colorless, as well as transition in the state of matter i.e. solid to liquid.
Whereas a chemical change is one where there is no modification in physical appearance in most cases.
However, in some cases there can be variation in the physical features too.
The chemical change mostly involves a modulation in the chemical nature of the molecules or atoms within the matter.
Chemical alteration of the molecules can modify the appearance in terms of color or texture and sometimes even in the states of matter.
An example of chemical change is the formation of foam or effervescence when lemon juice is mixed with sodium bicarbonate.
Here what actually happens is when you add lemon juice into a powder of sodium bicarbonate, immediately there is a chemical modulation leading to the formation of carbon dioxide and sodium citrate salt.
The change occurs both physically as well as chemically.
Differences Between Chemical and Physical Change
| Sl. No | Feature | Physical change | Chemical change |
|---|---|---|---|
| 1 | Appearance | Always there is a in alteration physical appearance | Physical appearance may remain same due to the chemical change |
| 2 | Chemistry | The chemistry is Intact. | The chemistry is modified. |
| 3 | Occurs when | Exposed to Physical force, pressure or a differences in the temperature | Exposed to high temperatures or mixing with other substances |
| 4 | Occurs due to | A physical change occurs due to a alteration in intermolecular forces of attractions or energy states of bonds. | Chemical change occurs due to an interaction between two or more substances |
| 5 | Extent of variation | Only at interatomic or molecular bonds but no involvement at the atomic or molecular level | Occurs at atoms, molecules, their arrangement or even change inter-molecular force of attraction |
| 6 | Rate of transition | Comparatively, physical modification in most cases is slower and proceeds over a period of time | Chemical modification is very quick like in fraction seconds in most cases and occurs instantly. |
| 7 | Control or Regulation | The transition can be stopped midway from further progress | The modification is hard to be stopped from further progress. |
| 8 | Reversal | Physical transformation in some cases can be completely reversed. | Chemical transformation is mostly irreversible. |
| 9 | Occurrence | Physical variation rarely occurs in nature or does not occur on a regular basis. Example; conversion of water into water vapor | Chemical variation is a common phenomenon in nature. It occurs on regular basis Example; Like biological oxidation. |
| 10 | Examples in laboratory | Conversion of wax into liquid | Acid base neutralization. |
Difference Between Chemical And Physical Change
Other examples for chemical changes include
- Transition in the color of potassium permanganate when reacted with oxalic acid.
- Precipitate formation of Silver chloride when silver nitrate reacts with Chloride ions in water.
Other examples of physical changes include
- The solid form of ghee when heated melts to liquid form and when cooled again converts to solid.
- Metals like iron when heated expand with red coloration due to excess temperature. But, again condense on cooling down.