Due to many chemical experiments in labs we always come across chemical and physical changes.
The key differences between chemical and physical change is seen in terms of visible change in forms.
In physical change there is always a change 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 change.
The Physical change can be seen as a change in color, state of matter (change from solid liquid or gas), the temperature or the texture.
An example for physical change Is conversion of ice into water. Here you can notice the physical change occurs in terms of change in color white to colorless, as well as change in state of matter i.e. solid to liquid.
Where as a chemical change is one where there is no change in physical appearance in most cases. However they can lead to change in physical appearance also in a few cases.
The chemical change mostly involves change in the chemical nature of the molecules or atoms within the matter.
chemical Change of the molecules Can change the appearance in terms of change in color or change in texture and sometimes even change in the state 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 chemical change 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 change in physical appearance | Physical appearance may or may not change due to the chemical change |
| 2 | Chemistry | The chemistry is not changed. | The chemistry is changed. |
| 3 | Occurs when | Exposed to Physical force, pressure or a change in the temperature | Exposed to high temperatures or mixing with other substances |
| 4 | Occurs due to | Physical change occurs due to change in inter-molecular forces of attractions or energy states of bonds. | Chemical change occurs due to an interaction between two or more substances |
| 5 | Point of change | Only at inter atomic or molecular bonds but no involvement at atomic or molecular level | Occurs at atoms, molecules, their arrangement or even change inter-molecular force of attraction |
| 6 | Rate of change | Comparatively, physical change in most cases is slower and proceeds over a period of time | Chemical change is very quick like in fraction seconds in most cases and occurs instantly. |
| 7 | Control or Regulation | Physical change can be stopped from further the progress | Chemical change is hard to be stopped from further progress |
| 8 | Reversal | Physical change in some cases can be completely reversed. | Chemical change mostly is mostly irreversible. |
| 9 | Occurrence | Physical change rarely occurs in nature or does not occur on a regular basis. Example; conversion of water into water vapor | Chemical change 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 change include
- Change of 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 change include
- 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.