As we have already discussed the three states of matter, we will now look a bit deeper to understand these categories’ nature. The change in the state of matter changes the arrangement of every particle and the bond between them. Here is how you can distinguish between solids, liquids and gases.

Solid is a matter that has a fixed shape and volume. All solid matter shares a strong intermolecular bond, due to which they tightly pack with each other. Due to the strong bond, particles get less space to move freely, but they can vibrate whenever any external force is applied. As the particles bond compactly to each other, there is less space between them. Solids can change their shape by breaking or cutting them using an external force, but their volume remains the same in every condition.

Here are a few key highlights of solids:

• Solid is known to be a fundamental state of matter.
• It is the rigidity that separates solids from liquids and gases.
• The strong intermolecular forces bind together with no room to move freely in solids.
• Solids have the least thermal expansion property and compressibility.

In liquids, the particles are wide apart and have weaker bonds. It is why liquids don’t have a definite shape; instead, they take the shape of the container they occupy. But liquids do have an actual volume that is independent of pressure. When you transfer a liquid from one container to another, the volume remains the same if the temperature and pressure do not change.

Here are a few key highlights of liquids:

• The molecules in liquids are loosely packed due to the weak intermolecular forces.
• These molecular forces are stronger than gases but weaker than solids.
• There is much space between the molecules of liquids, due to which they can move more freely compared to solids.
• Liquids tend to take the shape of the vessel they are poured in.

Gases are the third and the freest state of matter. The molecules are far apart in gaseous form, and they share almost negligible intermolecular bonds with each other. Gases don’t have any fixed volume or shape. They tend to occupy the entire vessel in which it is contained.

Here are a few key highlights of gases:

• The molecules don’t share any intermolecular bond in gases form.
• This state of matter neither has any fixed volume or fixed shape.
• All the molecules of this state move around in the vessel freely.

One of the most important and critical topics of this chapter is the law of conservation of mass. According to this law, mass can neither be created nor destroyed in an isolated system. Mass can only transform from one form to another.

In physics, the law of conservation of mass is expressed using a continuity equation of fluid mechanics. The representation is –

∂ρ / ∂t+ ▽ (ρv) =0

Where,

ρ is the density

t is the time

v is the velocity

▽ is the divergence

The process of combustion and various chemical reactions are examples that help in understanding the law of conservation of mass better.

All the particles that exist in the universe are a part of the matter. These particles have kinetic energy and based on their form, this energy also changes. Where solids have the least amount of kinetic energy in their particles, gases have the most due to the excessive intermolecular space. This theory also justifies the explanation of the change of state of the matter.

The kinetic molecular theory of matter states that all matter in the universe comprises constantly moving particles. All these particles have energy stored inside them, but the amount of that energy depends on the matter’s temperature.

1. What are the three common states of matter?
   The three states of matter are solids, liquids and gases. It is the molecular space in the matter that defines its state.
2. Is matter created or destroyed?
   According to the Law of Conservation of Mass, the matter cannot be created or destroyed. The universe’s total mass and energy are constant.
   
3. Is matter also energy?
   The mass of these three particles is less than a neutron’s mass, so each of them still gets some energy. Energy and matter are the same and fully interchangeable. So, in a way, energy, matter, space and time are all facets of the same thing.