Examples and Non-Examples of Chemical Reactions

Introduction

Every day we come across changes in our surroundings. These changes may involve one or more substances. Curdling of milk, dissolving of sugar, sometimes milk changes its taste, etc., are some examples of changes. 

We know that there are several changes happening in our surroundings and in our daily lives. Changes can be classified into two types: 

1. Physical change 

2. Chemical change

Explanation:

Physical change: Any change in the shape, size, and color of a substance is known as a physical change. 
When any substance is undergoing any physical change, no new substance will be formed. The physical properties of the substance change then it results in a physical change

Chemical change: The type of change in which the substance undergoes changes and forms two or more new substances is known as chemical change. This chemical change is also called a chemical reaction because the chemical composition of the substance changes.   

What is a Chemical Reaction? 

The reaction in which one or more substances combine or change to form one or more new substances is known as a chemical reaction. 

One or more reactants combine and give the new product. A reaction has a left side and a right side. The reaction between the reactants is represented with the ‘+’ sign, and the relation between the reactants and the products is denoted with: 

Examples of Chemical Change and Reactions: 

Rusting of iron:  

When an iron rod or iron substance is exposed to air, it chemically reacts or combines with oxygen and moisture present in the air to form a reddish-brown colored flaky substance. This is called rust.  

This rusting of iron is also one of the very slow reactions. 

Food Color Change: 

When we cut the brinjal into pieces and leave it open or keep it exposed to the air, after some time, the color of the brinjal changes to brown color. This shows that the substance is exposed to oxygen. The changing of color is an example of chemical change. 

Curdling of Milk: 

The curdling of milk is where lumps are formed in the milk. Lactic acid is present in the milk. Milk contains proteins, and these proteins react with the lactic acid present in it. Lactic acid breaks the chemical structure/bonds in the milk and forms new bonds, by which it forms a semi-solid. 

This process is known as the curdling of milk. 

Digestion of Food: 

Digestion of food is one example of chemical change. When we eat food, it travels into the stomach and the intestine. In the stomach, the food particles break down into simpler substances so that the nutrients can be easily absorbed by the body. 

Burning of Wood/paper: 

The burning of wood or paper is one of the example of a chemical change, while cutting wood is an example of a physical change. When wood is burnt, it forms ash. 

Examples of Physical Change: 

Blowing of the balloon: When we blow the balloon, the size slowly increases, and it attains the shape of the balloon, where there is a change in the shape and size of the substance.  

Blinking of eyes:  

Blinking of eyes is one of the physical changes. It is one of the body’s functions. When you close and open your eyes within a second, it is called blinking. 

Frequently Asked Questions (FAQs): 

1. What is the evidence of a chemical change? 
   Chemical changes can be witnessed when there is a formation of precipitation, color change, gas formation, smell change, or changes in temperature. 

2. Is the digestion of food a chemical change? 
   Yes, the digestion of food is a chemical change that takes place inside our body. 

3. Is milk souring a physical change or a chemical change?  
   Souring of milk is a chemical change because the structure of the milk changes and is replaced by new chemical compounds. 

4. What is the difference between a physical change and a chemical change? 
   Physical change: Any change in the shape, size, and color of a substance is known as a physical change. When any substance is undergoing any physical change, no new substance will be formed.  
   Chemical change: The type of change in which the substance undergoes changes and forms two or more new substances is known as chemical change. This chemical change is also called a chemical reaction.