Difference Between Physical And Chemical Change

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A physical change as the name suggests, brings about a change in the physical state of matter under suitable conditions. The physical change occurs when there is some change either in spaces or forces. The chemical identity of the substance does not change in physical change. The intro versions of states is a physical change because these changes occur without a change in composition and no change in the chemical nature of the substance. Although ice, water and water vapour all look different and display different physical properties, they are chemically the same. For example Crystallization of copper sulphate, dissolving of salt in water.

A few important characteristics associated with physical changes are listed.

1. A physical change involves a change in the physical state of a substance by changing either the inter particle spaces.

2. There is no change in the composition of the substance.

3. The substances undergoing physical change do not change their main characteristics.

4. No new substance is formed.

5. The change is temporary and can be reversed by reversing the conditions ...
... which cringe about the change.
Chemical Changes

Both water and cooking oil are liquid but their chemical characteristics are different. They differ in odour and inflammability. We know that oil burns in air whereas water extinguishes fire; It is this chemical property of oil that makes it different from water. Burning is a chemical change. During this process one substance reacts with another to undergo a change in chemical composition. Chemical change brings change in the chemical properties of matter and we get new substances. A chemical change is also called chemical reaction. Chemical change as the name suggests, brings a change in the chemical composition of the matter. During, this there is and exchange of their constituents and new substances are formed. For example Conversion of milk into curd, rusting of iron nails, Burning of coal etc.
Characteristics Associated with Chemical Changes:

A few important characteristics associated with chemical changes are listed.

1. As a result of chemical change, the physical state of the substance may or may not change.

2. There is always a change in the chemical compositions of the substance.

3. There is also change in characteristics of the substance.

4. New substances are always formed

5. The chemical change is of permanent nature and cannot be easily reversed.

The word ‘equilibrium’ is related to the Latin word ‘Libra’ means balance. From the ancient times, users of the balance have known that when the balance does not turn in either direction, the two forces are equal. When two states of body or a physical system are in rest or in continuous motion or without acceleration are called Physical equilibrium.

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Different Types of Physical Equilibrium

There are different types of equilibrium. They are-

Thermal Equilibrium
Mechanical Equilibrium
Static Equilibrium
Rotational equilibrium

Thermal Equilibrium- In thermodynamics the state of a system is an equilibrium state if the macroscopic variables that characterize the system do not change in time .For example a gas inside a closed rigid container, completely insulated from the surroundings, with fixed values of pressure, volume, temperature, mass and composition that do not change with time, is in a state of thermodynamic equilibrium.

Mechanical Equilibrium: When the net forces applied on a body are zero is call Mechanical equilibrium. The net forces mean the sum of all forces to the object and the sum of all torque on the object. If an object is moving without acceleration then also it is in Mechanical Equilibrium. Example of Mechanical Equilibrium: If a person tries to push spring after sometimes the spring will not compress because it will reach the condition when the static force and resistive force of spring are equal. That is the situation of mechanical equilibrium.

Image of Mechanical equilibrium

Image of Mechanical equilibrium

Static equilibrium- Static equilibrium is a part of mechanical Equilibrium’s body is resting under gravity on a horizontal surface is an example of Static Equlibrium.If two forces of same magnitude is applied on a body, the state of that body will not change, because they are balancing each other.

forces F1 and F2

The force F1 and F2 are same in magnitude but in opposite direction (denoted by ‘+’ and ‘–‘sign), so the resultant force,

+F1 + (-F2)

+F1-F2=0

Rotational Equilibrium: Lever rotates through a small angle. The masses of one side go up and other in down.In figure

rotational equilibrium.

The mass of the lever M1 goes down d1 ?? and mass M2 goes up by d2??.the total potential energy V of the two masses changes by

?V= -M1g d1 ?? + M2g d2??.

= (F2d2-F1d1) ??,

When no change of potential energy then M2gD2 = M1gD1,

So in equilibrium condition,

F1d1 = F2d2

This is called rotational equilibrium.
Conclusion for Physical Equilibrium

From the discussion on physical equilibrium, the types of equilibrium mentioned above may change due to change of any dependent variable on that equilibrium state.

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