II. Change of state of matter 

Solid-state, liquid-state, and gaseous-state are three states of matter, and any physical change in their state is called a change of state of matter. These changes are reversible in nature means they can attain any state again and again. This reversible property of the three states depends upon different parameters and conditions which will be discussed below.

A physical change in a matter is referred to as a change of state of matter. They are reversible modifications that do not require any changes in the matter’s chemical composition. Melting, freezing, sublimation, deposition, condensation, and vaporization are examples of common state transitions. We can understand the meaning of a change of states of matter in one more way i.e. when a solid is heated it changes into liquid, and when a liquid is heated it changes into a gas, and when a gas is cooled it changes to a liquid when a liquid is cooled it changes to solid. And we can interchange these states by: 

• Changing Temperature.

 • Changing Pressure. 

Why do States of Matter Change?

The change in state occurs due to the following factors:

 • Changing the Temperature

• Changing the Pressure

 • Changing the Intermolecular Space and Force of Attraction 

• Changing the Kinetic Energy of Particle 

Let’s learn about them Changing the Temperature and Changing the Pressure and the other in detail.

 II.1. Changing the Temperature 

The temperature effect on heating a matter depends upon the nature of the matter and the conditions required in bringing the change. So, let’s discuss all the 6 interchanges between these states now.

 II.1.1. Solid to Liquid change 

This process is known as Melting. 

The process in which a solid substance changes into a liquid on heating is called melting. On increasing the temperature of the solid the kinetic energy of the particle increases which overcomes the force of attraction between the particles thereby solid melts and is converted into liquid. 

II.1.2. Liquid to Gas change

This process is known as Boiling or Vaporization. The process in which a liquid change into gas rapidly on heating is called boiling. The temperature at which a liquid boils and changes rapidly into gas at atmospheric pressure is called the boiling point of the liquid. 

II.1.3. Gas to Liquid Change 

This process is known as Condensation. The process of changing gas into liquid by cooling is called condensation. Condensation is the reverse of boiling. 

II.1.4. Liquid to Solid Change 

This process is known as Freezing. The process of transformation of liquid into a solid by cooling is called freezing. Freezing means solidification. It is the reverse of the melting process.

II.1.5. Solid to Gas Change 

This process is known as Sublimation. The change of solid directly into vapor on heating without passing through the intervening liquid state is called sublimation. The common substances which undergo sublimation are ammonium chloride, iodine, camphor, naphthalene, and anthracene. For example, Solid carbon dioxide (or dry ice) sublimes to form carbon dioxide gas. Naphthalene balls disappear with time without leaving behind any residue. 

II.1.6. Gas to Solid Change

 This process is known as Deposition or De-sublimation. It is a thermodynamic process in which gas changes into a solid directly without entering into the liquid phase. 

II.2. Changing the Pressure

 The physical state of matter can also be changed by changing the pressure. By applying high pressure, the particles of a gas can be brought close together means gases can be liquefied easily by applying pressure and reducing temperature. When pressure is applied particles come together thus the force of attraction increases and intermolecular space decreases. Hence, gas liquefies. When pressure around the solid carbon dioxide is reduced its temperature increases and it directly changes into carbon dioxide gas. 

II.3. Inter-conversion 

of Three States of Matter The states of matter are inter-convertible. The state of matter can be changed by changing the temperature or pressure. The transition of one state to another is referred to as the interconversion of matter. It is a process in which matter transitions from one state to another and then returns to its original state with no change in its chemical makeup. Heating may transform solids into liquids.