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An Introduction to Phase - State of Matter

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Whenever we discuss thermodynamics within the realms of Chemistry, the prospect of “phase” plays a significant role. In essence, the idea of a phase of a matter can be understood via the changes in their state that occur with differences in their surrounding temperatures and other conditions. However, such differences in the state of matter do not alter the chemical composition of the matter. To put it simply, the phase state of matter is a homogenous quantity, meaning it is constant in its chemical composition.  


States of Matter Diagram 

As most know, the three fundamental states of matter that are the most prevalent in our day to day lives are- Solid, Liquid and Gas or Vapour. The reason why these three are the most prevalent forms of thermodynamic phases is that they are the three phases that we are the most accustomed with. We have seen how water exists in its liquid form in lakes and oceans, whereas it exists in its solid form in icecaps and also, how it exists in its gaseous form when water is boiled on the stove. Thus, we are aware of the three primary phases of matter. However, the prospect of phase within the context of matter and its states is not limited to the three aforementioned states only. Other phases that exist, or are at least, considered, include- Amorphous, Colloid, Crystalline, Plasma and Glassy phases. Out of these, the phase catering to the Plasma state is considered the most prevalent. 


In the thermodynamic phase of Plasma, the number of charged particles that comprise within the matter become roughly equal in number, which leads to the ionization of the gas of the matter since both the positively and the negatively charged particles become equal in number. Therefore, the state of Plasma is often considered the fourth phase of matter, after the solid, liquid and gaseous phases. The provided diagram can be referred to for further clarification. 

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What is Phase in Chemistry 

As has been discussed so far, the idea that is emblematic of the thermodynamic states of matter is largely relevant to the field of Chemistry, as well as that of Physics. Since these two fields are cut from the same fabric of Science, it is incredibly difficult to look at the subject of phase through the single lens of either of the two fields. Therefore, with regards to the aspect of phase in Chemistry, it is reasonable to state that, although the idea catering to the implementation of matter and its states falls primarily in the realm of Chemistry, the significance of Physics on the same idea cannot be discounted.


Therefore, to elaborate on the idea of the study of phases of matter in Chemistry, as we have discussed thus far, the phase definition Chemistry refers to the thermodynamic states of matter that are homogeneous in nature, where a matter solidifies, liquifies or evaporates with regards to the changes in its surrounding temperature and other influencing factors. Therefore, as can be inferred, the definition of Phase in the field of Chemistry remains the same as that of the Physical field.


Phases of Matter 

Since the three primary types of phases within the context of any matter are- Solid, Liquid and Gas, as has been mentioned earlier, it is important to consider the prospect of phase change. By its definition, the concept of phase change occurs when a matter goes through an alteration in its form and enters another form. For instance, when we freeze water in the freezer, it goes from being in the liquid phase to being in the solid phase, thereby, a phase change occurs in the water. 

Now, to answer the question, “What is phase in thermodynamics?”, we must consider the various phases of matter and how they are defined. 

Solid: In this state of matter, there is a decrease in the atom energy, leading to the formation of a three- dimensional structure. For example, a cube of ice


Liquid: In this state of matter, the structure of the matter is malleable, i.e., it takes the form of the vessel that it is poured inside of. For example, water in a jar. 


Gas: In this state of matter, the structure of the matter is gaseous, meaning it cannot hold any particular shape or structure. For example, the vapor from boiling water.


Did You Know? 

  • Gases are able to fill up any container as long as it is closed and has a volume. This is why gases are used to fill balloons of various shapes and sizes, instead of a liquid.   

  • The molecules of gases move chaotically in vast numbers. 

  • The idea of Phase Change was proposed by J. Willard Gibbs in 1876. 

FAQ (Frequently Asked Questions)

1. Define the Plasma Phase of Matter. 

Ans: The three primary phases of matter are, Solid, Liquid and Gas. However, the phase of Plasma is still considered the fourth phase following the three phases. This is because, in the thermodynamic phase of Plasma, the number of charged particles that comprise within the matter become roughly equal in number, which leads to the ionization of the gas of the matter since both the positively and the negatively charged particles become equal in number. Therefore, the state of Plasma is often considered the fourth phase of matter, after the solid, liquid and gaseous phases of matter and is considered important.  

2. What is meant by Phase Change? 

Ans: The concept of phase change occurs when a matter goes through an alteration in its form and enters another form. The reason why phase changes occur is that, whenever there is the provision of the supply (or loss) of sufficient energy, the phase of a matter begins to alter. For instance, when a liquid matter is frozen, it turns solid and when a solid matter is melted, it turns liquid. Similarly, when a plasma matter is recombined, it turns gas, whereas a gaseous matter turns plasma when it is ionized. Therefore, this is how phase change occurs in most matters.