States of Matter - Notes, Topics, Books. FAQs

“Successful and unsuccessful people do not vary greatly in their abilities. They vary in their desires to reach their potential.” – John Maxwell

In the universe, matter exists in three different forms, i.e solid, liquid and gas. The characteristic properties of materials that we can see are of the bulk but not of the single particle. Physical properties of the matter may change in different physical forms but chemical properties do not change. For example water, it can exist in three different forms, i.e ice, water and gas. In all of its three forms, its physical properties are different from each other but chemical properties remain the same. There are other states of matter exist as well but those are beyond the scope of this chapter.

In this chapter, you will study the properties of gases and liquids. As we all see in the universe these fluids in bulk but the states of matters chapter gives you the depth of these fluids at the molecular level. The properties of gases vary according to the change in pressure and temperature. The laws like, Boyle's law, Charle's law, etc. will explain all these phenomena later.
There are various real-life examples available which help us to understand the phenomena of fluids.

• The diffusion of the fragrance of an incense stick in the whole room. This phenomenon works on the concept of the diffusion of gas molecules in the room. These velocities have been described in this article later.
  
• In scuba diving, as we go down in the water the pressure increases due to which the air present in the lungs is compressed. Now, as we come out of the water, it is advised to release the air in a controlled way otherwise the divers can suffer through injuries.
  
  There are various other aspects every time available around us so if you really want to dissolve this chapter in each and every cell of your body then just correlate everything that you see and observe with the concepts given in this chapter.

Notes for the States of Matter

In this section, you will study about the important topics of the chapter, overview, formulae and some important tips and guidelines for the preparation of the chapter at the best.

Important Topics of States of Matter

• Difference between solid, liquid and gas
• Boyle's law
• Charles' law
• Gay Lussac's law
• Avogadro's law
• Ideal gas equation
• Dalton's law of partial pressure
• Graham's law of diffusion
• Kinetic theory of gases
• Vrms, Vavg, Vmp values
• Real gas equation
• Compressibility factor
• Liquefaction of gases

Overview of the States of Matter

In the universe, matter exists in three different forms, i.e, solid, liquid and gas. All these three forms are equally important in their own forms such as solids like chair we use for sitting and the car we use for travel. Liquids like water are important for drinking and gases like oxygen are important for breathing, etc.

The table given below explains the major differences between the solids, liquids and gases.

Gas Laws

For explaining the phenomena of the gases, researchers over the years have developed various laws i.e, Boyle's law, Charle's law, Avogadro's law, etc.

For explaining the phenomena of the gases, researchers over the years have developed various laws i.e, Boyle's law, Charle's law, Avogadro's law, etc.

Important laws for gases

(i) Boyle's Law: This law states that at constant temperature and amount of gas, the pressure of a gas is inversely proportional to its volume. Mathematically, this can be represented as follows:
Where k is proportionality constant.This law can also be represented as follows:
This law can also be expressed graphically. In the graph given below, the pressure of the gas is being measured at different temperatures.

(ii) Charles' Law: This law states that for every 1⁰ rise in temperature for fixed amount of gas, the volume of a gas increases by of the original volume of the gas at 0⁰C. Mathematically, this law can be represented as follows:

The graph below shown is of the different isobars, which are depicting the increase of volume on increasing the temperature.

(iii) Gay Lussac's Law: This law states that for a fixed amount gas at constant volume, the pressure is directly proportional to the temperature.
where k is proportionality constant. This law can be understood from the graph given below as well. In this graph, the pressure is increasing with the increase in temperature at different volumes of gas.

(iv) Avogadro's Law: This law states that equal volume of all gases at the same temperature and pressure contain equal number of molecules

Ideal Gas Equation
The three given laws when combined together in a single equation then that is known as ideal gas equation.
Thus,Therefore,

R = Universal gas constant and has value 8.314Jk-1mol-1s

(vi) Dalton's Law of Partial Pressures: This law states that the pressure exerted by the non-reactive gases is equal to the pressure exerted by the individual gases. In this case, the pressure exerted by the individual gases is called partial pressure.
Here p₁, p₂, p₃... are the partial pressures of individual gases

Kinetic Theory of Gases

This theory was proposed to understand the behaviour of gases in a better way. This is known as 'kinetic theory of gases'. The main postulates of this theory are as follows:

• The gas is comprised of a large number of tiny particles known as molecules. These molecules are completely identical in size, shape and mass.
• The volume of a single molecule is very small as compared to the total volume of a gas.
• There is no force of attraction and repulsion between these gaseous molecules.
• The molecules of these gases are always in constant and random motion.
• The molecules of the gas always move in random in directions in straight lines. During this motion, these particles collide with each other and with the walls of the container.
• Collisions of the molecules are perfectly elastic and thus their energy is always conserved before and after the collision.
• At any instant of time, these molecules move with different speed and thus these molecules have different kinetic energies.

Behaviour of Real Gases

All the laws that we have studied so far are applicable to the gases if we assume that these gases are ideal gases. But in reality these gases behave quite differently and thus these gases are known as the 'real gases'. In the figure below, the deviation of the behaviour of gases is shown.

To analyse the real gases behaviour, pV vs p curve is plotted. In this curve, helium and hydrogen gases are showing positive deviation from an ideal gas. Other two gases like carbon monoxide and methane are showing negative deviation to a certain point after that these gases cross the ideal gas and show the positive deviation. This deviation of the behaviour of gases from ideal gas is mainly because of two factors:

• There is a force of attraction between the gas molecules exist. Thus the gases liquify at high pressure and low temperature.
• Volume of the gas molecules is not negligible as compared to the space containing it.

On the basis of these observations, a new gas equation was given also known as van der Waals equation. Mathematically, it can be written as below:
here, n is the number of moles of gas and a and b are van der Waals constants and their value depend on the properties of the gas.

The deviation of gases from ideal behaviour is expressed in terms of the compressibility factor(Z), which is represented as follows:

• For ideal gases, Z=1.
• For real gases, either Z>1 at high pressures or Z<1 at intermediate pressures.

Liquefaction of gases

There are three main terminologies that we used to describe the liquefaction of gases.

• Critical Temperature: It is the temperature above which any gas does not remain liquid. For carbon dioxide, this temperature is.

• Critical Pressure: It is the pressure at any particular temperature at which a gas starts to liquify. At pressures higher than this value, the gas remains as a liquid. For carbon dioxide, this value is 73 atmospheric pressure at .
• Critical Volume: It is the volume of one mole of a gas at critical temperature.

Liquid State: Liquid is one of the three forms of matter. In liquids, intermolecular forces are stronger than gases but weaker than solids. Thus these have a tendency to flow and occupy the shape of the container. There are few important properties that you need to consider such as vapour pressure, surface tension, and viscosity.

How to prepare for States of matter?

• This chapter is a part of Physical chemistry. This chapter is one of the most important chapters of the complete chemistry syllabus. Its concepts, laws, numericals and graphs all are important both for basic foundation of chemistry and for scoring good marks in the examination.

• Before reading this chapter, first, you must have the basic knowledge of the mole concept.

• You must observe why gases are not ideal in real and on what conditions these gases become ideal. Learn carefully about the graphs as some questions will be direct from graphs.

• Rest this chapter is very simple, just be regular and be consistent in your numerical practice.

Prescribed Books for the States of Matter

First, you must finish the class XI NCERT textbook and solve each and every example and unsolved question given in it. Then for advanced level preparation like JEE and NEET, you must follow R.C. Mukherjee and O.P. Tandon. You must definitely solve the previous year papers. Meanwhile, in the preparation, you must continuously write the mock tests for the depth of knowledge. Our platform will help you to provide with the variety of questions for deeper knowledge with the help of videos, articles and mock tests.