August 2023

Chemical Change : A process in which new substance(s) are formed, is called chemical change.

Examples of chemical changes are :

1. Souring of milk(milk left at room temperature during summer) : This is an example of chemical change because if we taste sour milk ,It is sour and unpleasant and its identity and nature is different from fresh milk which indicates the formation of some new substances.
2. Rusting of iron : Iron oxide forms in the process which is completely different from iron. So this is an example of chemical change.
3. Cooking of food : Chemicals present in food form new substances when we supply heat to the food,so this is an example of chemical change.
4. Ripening of fruits : When fruits get ripened ,its identity,nature and taste is different from raw fruits which indicates that this is an example of chemical change
5. Digestion of food : Digestion means breaking of food into simpler substances. Food contains chemicals like fats,carbohydrates,protein etc. These chemicals are broken down into simpler substances by our various digestive organs such as liver,pancreas,intestine. When the fats,carbohydrates and protein are broken down by our digestive system ,the new substances formed have different identity and nature. Therefore,digestion of food is an example of chemical change.
6. Respiration in our body : In our daily life ,We tell or understand respiration as inhalation or exhalation but Scientifically respiration is a not inhalation or exhalation.It is the process in which glucose in our body reacts with oxygen and forms carbon dioxide ,water and energy. As this is a process in which new substances are being made,so this is an example of chemical change.

Chemical Reaction : A process in which new substance(s) are formed is called chemical reaction.

Clearly ,Chemical change and chemical reaction have same definition, So you will ask that what is the difference between chemical change and chemical reaction because both have same definition?

Simply speaking both are same but in a chemical change, we don’t focus on the detail of new substance formed in the process ? We do not investigate which are the initial and final substances and what are their names ? We just check nature,identity and taste of the new substance formed in the process to identify a chemical change. But in a chemical reaction ,We focus or investigate which are the initial substances and what are the final substances formed in the process. We also write the names of initial and final substances formed in a chemical reaction.In a chemical change like cooking of food( protein, fat and other chemicals in food react with oxygen with help of heat),there may be many reactions involved but in a chemical reaction there is only one reaction

Now we can say that whenever a chemical change happens,there occurs a chemical reaction and vice-versa.