Difference Between Chemical and Physical Reaction

Introduction

There is a continuous change that is going on around us all the time. The base of these changes is the reactions that occur. We know the fact that actions and reactions are the two sides of the same coin. Hence, the environment that surrounds us is subjected to different reactions which lead to its change. In science, this reaction can be divided into two major parts – chemical reaction and physical reaction. These reactions are nothing but the various kinds of changes that occur either naturally or artificially due to the introduction of a different substance into the existing environment. Physical and chemical reactions are the two types of changes in matter and there exist some major differences between the two which shall be discussed in this article.

Chemical Reaction vs Physical Reaction

The key difference between a chemical reaction and a physical reaction is that when a substance undergoes a chemical reaction, it no longer remains in its original form. The original compounds changes as a result of the reaction. On the other hand, a physical reaction is that type of reaction where the substance that undergoes a reaction remains the same while only its state or shape changes. The physical reaction is a temporary change. On the other hand, the chemical reaction leads to the permanent change of the matter or substance. Despite the changes that occur, the total energy in both these reactions remains the same i.e. the energy is intact in both physical and chemical reactions.

Differences Between Chemical Reaction and Physical Reaction in Tabular Form

Parameters of Comparison	Chemical Reaction	Physical Reaction
Definition	A chemical reaction is a type of reaction where the chemical composition of a substance undergoes changes.	On the other hand, when the physical properties of an element change, it is known as a physical reaction. Here, the molecular properties remain intact.
Energy absorption	The absorption and evolution of energy take place during a chemical reaction.	On the other hand, there is very little or no absorption involved when a substance undergoes a physical reaction.
Type	A chemical reaction is a permanent type of change.	A physical reaction, on the other hand, is a temporary type of change.
Changeability	The original substance cannot be recovered in a chemical reaction. This means that a chemical reaction is irreversible. It cannot be changed.	On the other hand, physical reactions are easily reversible. The original substance can be recovered even after undergoing the reaction.
Production of energy	Energy, such as sound, heat, light etc. is generated in a chemical reaction.	In a physical reaction, there is no generation of any energy.
Substance formation	A chemical reaction is always accompanied by one or more than one newly formed substances.	Whereas, a physical reaction, is not always accompanied by the formation of new substances.
Examples	Some examples of a chemical reaction are: digestion of food, burning fuels, rusting of iron, baking a cake, acid-base reaction and so on.	Some examples of physical reactions are: boiling water, melting ice, chopping wood, folding a paper, dissolving salt or sugar in water and so on.

What is a Chemical Reaction?

Chemical reactions are the processes that lead to the chemical change (transition) of one chemical substance into another with a different chemical identity or composition. The modification is irreversible and cannot be restored. The basic components and the finished result are chemically distinct.

Chemical reactions are important in many businesses, cultures, and even in our daily lives. They are always occurring in our environment, such as iron rusting, ceramics, alcohol production, and so on. The compounds existing at the start of the reaction are referred to as "reactants," while the freshly formed compounds are referred to as "products." The number of parameters in the reactant molecules equals the number of components in the products. 

Chemical Reaction Indicators

There are various indicators of the chemical reaction. Some of the most common ones are as follows:

1. A change in colour of the substance leads us to know that a chemical reaction has occurred.
2. If a reaction emits heat, sound or light, then that reaction can be an indicator of the chemical reaction. For instance, during combustion, when there is a fire or a spark, it indicates that a chemical reaction has occurred.
3. When there is the formation of precipitation or reaction with liquid reactants, then there is an indication that a chemical reaction has occurred.
4. When a substance reacts, there might be certain bubble formation or even sometimes, there is vapour formation. This indicates that there is a chemical reaction.

Types of Chemical Reactions

There are various types of chemical reactions. Some of them are described as under:

Decomposition Reaction

When the reactants break down into simpler substances, then that reaction is termed a decomposition reaction. For instance, if we take two substances A and B, the decomposition reaction between them would be:

AB ----- A + B

Combustion Reaction

It is such a type of reaction that it releases energy, generally in the form of heat. It is a chemical process that occurs amid fuel and an oxidant to produce fumes, water, and temperature. The smouldering of naphthalene is an example of a combustion reaction.

Combination Reaction

In such a reaction two or more compounds are together combined to form a single compound. Decomposition and combination reactions are opposite to each other. 

Neutralization Reaction

Here, acid and base react with each other to form salt and water. The formula for this reaction is:

Acid + Base = Salt + Water

Precipitation Reaction

When two soluble chemicals combine to produce an insoluble solid, a precipitation reaction takes place. The precipitant is the solid that separates from the solvent.

Redox Reaction

This reaction is also known as oxidation-reduction. This type of reaction may involve the transfer of electrons between chemical species. The addition of oxygen into the reaction is termed oxidation and the removal of oxygen or the addition of hydrogen into the reaction is termed reduction.

What is a Physical Reaction?

A physical reaction is a process that involves a change in the physical characteristics of a substance. A material undergoes a process that alters its physical properties while maintaining its chemical composition. The modification is just transient and may be readily reversed. Physical reactions modify the shape and size of matter but do not change its composition. Alteration in equilibrium, dissociation of a combination, structural displacement, solution implementation, and many others are some examples of physical reactions. A physical reaction is fully reversible, which means it may be returned to its original state. The modifications are not very permanent and can be converted using simple physical procedures. A component with a particular shape, dimension, quantity, and so on changes either spontaneously or by physical operations.

Physical Reaction Indicators

The signs that are associated with a physical reaction to a substance are as follows:

1. There is a change in the state of the matter of the substance in any physical reaction.
2. No new substance is formed while there is a physical reaction going on.
3. Physical reactions are easily reversible.
4. If there is a change in the size or the shape of the substance in a reaction, that reaction is termed a physical reaction.
5. There is also a slight change in the colour of the matter in any physical reaction.

Types of Physical Reaction

The various types of physical reactions are described as under:

1. Dissolving: the dissolution of two or more substances into a liquid is termed dissolving. For instance: the solution of salt or sugar in water is an example of dissolving which is a physical reaction because there is no change in the solvent.
2. Solidification: also known as freezing, it is the removal of heat from a substance to convert it from a liquid to a solid. The temperature must be lower than the freezing point of the material for the transformation to happen. Using a freezer to turn water into ice is an example of this physical transformation.
3. Melting: it is also known as thawing or fusion. Melting means when applied heat or pressure leads to the increase of the substance’s internal heat of any solid matter, resulting in a change of the solid to liquid form. For instance: when leftover ice in a glacier turns into a puddle of water, it is known as thawing or melting.
4. Condensation: condensation occurs when the substance turns from a gaseous state into a liquid state. One very common example of condensation or clouding is when water evaporates and forms into tiny water droplets in the sky and falls like drops of rain.
5. Boiling liquid: Boiling is the process of converting a liquid to gas via the use of heat. When the liquid reaches a certain temperature where the hydrostatic pressure matches the pressure of the air well above the fluid, this happens. The gas rises from the fluid at this degree, known as the boiling point or boiling temperature of liquids. Since there does not occur any change in this situation, hence it is known as one of the types of physical reaction. 

Differences Between Chemical Reaction and Physical Reaction in Points

1. A chemical reaction is one in which the chemical constituent of a material change. A physical reaction, on the other hand, occurs when the physical qualities of an element change. The molecular characteristics are preserved here.
2. In a chemical reaction, energy is absorbed rapidly, but in a physical reaction, there is little or no energy consumption.
3. If there is a physical reaction, the substance involved stays the same at the cellular level. Although the particles reorganize, the actual structure remains unchanged. It may appear different, yet it is built up of the same substance. A chemical reaction, on the other hand, happens when a reaction creates a change at the molecular level. The chemical makeup of the matter changes here, and there is the creation of a new substance.
4. Another significant distinction between physical and chemical reactions is the rate of conversion. Physical change happens quicker, perhaps instantly. Most chemical reactions, on the other hand, require a long period to manifest. When we crush a tin can, we can see physical changes. However, tin can deterioration happens gradually; it will take quite a long time before we notice the rust on the tin can.
5. A chemical reaction is followed by the formation of one or more new compounds. A physical reaction, on the other hand, is not necessarily followed by the production of new substances.

Conclusion

Thus, from the above description, it is seen that both physical and chemical reactions are necessary to understand the change and the transformation of any substance or matter. The only basis of living is changing. Without changes, there is no harm to life. This change is similar to the environment that surrounds us. Once in a while, the environment too needs to change. Hence, physical and chemical changes are the two types of changes that the environment around us requires. These reactions can range from extremely low to effective depending upon the elements acting on them.

We can understand from the above discussion that the primary difference between physical and chemical changes is that physical changes can be reversed. Whereas, chemical changes are usually non-reversible. A physical change is characterised by changes in the physical property of the material, such as volume, form, structure, aroma, look, thickness, and so on. A chemical change, on the other hand, refers to a change in the chemical compositions of a material, i.e. a change in its chemical makeup. For instance: since water can freeze, liquid can thus turn into a solid state. Even after its transformation, the substance obtained is still water. We can again melt ice to change it into a liquid form. Hence, boiling, melting, freezing etc. are all types of physical reactions. On the other hand, when we burn paper, we will get a new substance called ash. Here, we cannot turn back the ash into paper. Hence, burning, rusting, and digesting are all examples of chemical reactions because they cannot be brought back into their original states. 

References

• https://www.thoughtco.com/types-of-chemical-reactions-604038
• https://sciencing.com/10-types-physical-change-8455782.html