States of Matter

States of matter are fundamental to understanding the physical world around us, forming the basis of everything we see and touch. Matter exists primarily in three states: solid, liquid, and gas, each with unique properties that influence how substances behave in different conditions. In our daily lives, we encounter these states constantly—ice melting into water, water evaporating into steam, or air being compressed in a tyre. These transitions demonstrate the energy changes and molecular arrangements that dictate the state of a substance. Understanding these states not only provides insight into the natural world but also plays a crucial role in numerous technological and industrial processes, from refrigeration to the creation of various materials and fuels. In this article, we will discuss the study of matter's states, therefore, bridges our everyday experiences with the scientific principles that govern the universe.

What is Matter?

Matter is anything that has mass and occupies space. It is the substance that makes up the physical universe, from the smallest particles like atoms and molecules to the largest objects like planets and stars. Matter exists in different forms or states, such as solids, liquids, gases, and plasma, each characterized by distinct physical properties. These states are determined by the arrangement and energy of the particles within the substance. Matter is what everything tangible in the world is made of, whether it’s the air we breathe, the water we drink, or the ground we stand on. The states of matter are broadly classified into three states.

1. Solid

2. Liquid

3. Gas

However there is a fourth state (Plasma) also, but that is not in the scope of our syllabus.

Solid

A solid is a state of matter in which particles are arranged such that their shape and volume are relatively stable. In this, the constituents of a solid tend to be packed together much closer than the particles in a gas or liquid.

ΔS=∫msdtT=msln⁡(TfTi)

Liquid

A liquid is a state of matter which is a nearly incompressible fluid and it conforms to the shape of its container but retains a constant volume independent of pressure. It means that the volume is not changing with pressure.

Gas

A gas is defined as a state of matter consisting of particles that have neither a defined volume nor a defined shape.

Now, let's see the table given below of the comparison chart of solids, liquids and gases:

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Solved Examples Based on States of Matter

Example 1: A solid body of constant heat capacity 1 J/⁰C is being heated by keeping it in contact with reservoirs in two ways :

(i) Sequentially keeping in contact with 2 reservoirs such that each reservoir supplies the same amount of heat.

(ii) Sequentially keeping in contact with 8 reservoirs such that each reservoir supplies the same amount of heat.

In both cases, the body is brought from an initial temperature of 100 K to the final temperature of 200 K. The Entropy change of the body in the two cases respectively is :

1) ln⁡2,4ln⁡2
2) ln⁡2,ln⁡2
3) ln⁡2,2ln⁡2
4) In2,In8

Solution:

Solids

It is the type of matter that has got fixed shape and volume. The force of attraction between any two molecules of a solid is very large.

wherein

e.g.Nacl, Diamond, Graphite

ΔS=∫msdtT=msln⁡(TfTi)ΔS=1⋅ln⁡(TfTi)

ΔS is state-dependent. Its value changes by changing state hence it remains the same in the two processes.

ΔS=ln⁡2 for both but the temperature should be in Kelvin.

Hence, the answer is the option (2).

Example 2: Which of the following is more close to a black body?

1) blackboard paint

2) green leaves

3) black holes

4) red roses.

Solution:

A black hole cannot be considered as a black body as it does not emit anything while a black body is something that emits all of the energy that it absorbs.

Hence, the answer is the option (3).

Example 3: An external pressure P is applied on a cube at 0⁰C so that it is equally compressed from all sides. K is the bulk modulus of the material of the cube and is its coefficient of linear expansion. Suppose we want to bring the cube to its original size by heating it. The temperature should be raised by :

1) P3αK
2) PαK
3) 3αPK
4) 3PKα

Solution:

Bulk modulus is defined as

K=−ΔP(ΔVV)=−P(ΔVV)ΔV1=−PVK

Change in volume by heating
ΔV2=VγΔT=V⋅(3αΔT)ΔV2=3αVΔT

Since the net volume change is zero.
⇒ΔV1+ΔV2=0⇒−PVK+3αVΔT=0 or ΔT=P3αK

Hence, the answer is the option (1).

Example 4: Which of the statements is true for an ideal gas?

1) It has no shape or size.

2) Intermolecular force in gas is minimum.

3) They can be easily compressed

4) All of the above

Solution:

Gas

It is the type of matter which does not have a fixed shape or any fixed volume.

e,g, O2,N2,H2,He etc

Ideal gas - It is a hypothetical gas (which is not real gas), whose molecules occupy negligible space and have no interactions (Force of interaction is very less), and which consequently obeys the gas laws exactly.

Hence, the answer is the option (4).

Example 5: A gas molecules behave like

1) Inelastic rigid sphere

2) Perfectly elastic rigid sphere

3) Perfectly elastic rigid sphere

4) Inelastic non-rigid sphere

Solution:

Gas - It is the type of matter which does not have a fixed shape or any fixed volume. e,g. O2, N2,H2,He etc

Molecules of ideal gas behave like Perfectly elastic rigid spheres.
Hence, the answer is the option (3).

Summary

In this article, we explored the concept of matter and its primary states—solid, liquid, and gas—each characterized by unique properties and behavior. We also discussed real-life examples, thermodynamic principles, and solved problems related to entropy, bulk modulus, and ideal gas behavior. Understanding these fundamental concepts is crucial for grasping the scientific principles that govern the physical world around us.