Differences between chemical and physical change

Due to many chemical experiments in labs we always come across chemical and physical changes.

One of the key differences between chemical and physical change is seen in terms of appearance. 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 color change, in state of matter change that is solid liquid or gas  or in terms of temperature or change in texture.

Differences between chemical change and physical change-ice to water
Ice slowly converts to water changing its physical form

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.

Difference Between Chemical And Physical Change
Tablet containing sodium bio-carbonate and citric acid in compressed form react when exposed to water releasing CO2.

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 changeChemical change
1AppearanceAlways there is a change in physical appearance

Physical appearance may or may not change due to the chemical change
2ChemistryThe chemistry is not changed.The chemistry is changed.
3Occurs whenExposed to Physical force, pressure or a change in the temperature

Exposed to high temperatures or mixing with other substances
4Occurs due toPhysical 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
5Point of changeOnly at inter atomic or molecular bonds but no involvement at atomic or molecular  levelOccurs at atoms, molecules, their arrangement or even change inter-molecular force of attraction
6Rate of changeComparatively, 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.
7Control  or RegulationPhysical change can be stopped from further the progressChemical change is hard to be stopped from further progress

8 ReversalPhysical change in some cases can be completely reversed.Chemical change mostly  is mostly irreversible.
9OccurrencePhysical 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.

10Examples in laboratoryConversion of wax into liquidAcid base neutralization.

Difference Between Chemical And Physical Change

Other examples for chemical change include

  1. Change of color of potassium permanganate when reacted with oxalic acid.
  2. Precipitate formation of Silver chloride when silver nitrate reacts with Chloride ions in water. 

Other examples of physical change include

  1. Solid form of ghee when heated melts to liquid form and when cooled again converts to solid.
  2. Metals like iron when heated expand with red coloration due to excess temperature. But, again condense on cooling down.

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