Table of contents


Introduction to a thermodynamic system

Before moving towards the laws of thermodynamics, it is essential to clear our concepts regarding systems and surroundings since scientists discuss these laws in reference to these entities.

In chemistry, a system is a part where the reaction is taking place. For example, suppose we have ten moles of gas in a cylinder. Here the ten moles of gas are systems while everything around is its surrounding.

A system and surroundings are always separated from each other by a wall or a boundary. Thus, according to the example mentioned above, the wall of the cylinder is the boundary since it is separating the system from the surroundings.

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We can even define the surroundings more precisely as everything present outside the boundary is surrounding.

A boundary through which no matter can pass makes a closed system, while the boundary through which matter can pass develops an open system.

Don't forget that there's a clear difference between a closed system and an isolated system. The closed system is the one through which energy could pass but mass couldn't. On the other hand, an isolated system is the one through which neither mass nor energy could pass.

Remember that whenever we mention the term system, surroundings, open, closed, and isolated systems, we refer to the definitions mentioned above.

What is first law of thermodynamics

This law is also called the Law of Conservation of Energy and states;

"Energy can only transfer from one place to another or transform from one form to another. It could neither be destroyed nor created."

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The simplest example of the 1st law of thermodynamics is the sound coming from a speaker. We provide electrical energy to the device, which converts this electrical energy into sound energy. While some of the energy is also lost in the form of heat. You can see that no energy is produced during the entire process, but one form of energy is converted to another. Mathematically, we can write the same law as follows

∆E = w + q

According to this equation, the statement of the first law of thermodynamics can be described as

"The energy of a system(∆E) is the sum of work done(w) by the surroundings in a system and heat(q) flowing around its boundaries."

Explanation of 1st law of thermodynamics

  • According to the law, two factors affect the internal energy change of a system - work and heat.
  • As stated before, energy cannot be created nor destroyed; if energy changes in a system, it also changes in the surroundings.
  • If energy is flowing inside the system, it will do more work. Thus, the signs of w and q will be positive.
  • If energy is flowing outside the system, less work would be done. Thus, the signs of w and q will be negative.

As from the perspective of learning you should also learn about the periodic table and its history to understand its importance.

Second law of thermodynamics

The second law of thermodynamics states

"The entropy of an isolated system will never decrease and always increase."

Since no entropy loss occurs from an isolated system, it gradually moves towards the state of thermal equilibrium - the point at which a system possesses maximum entropy.

Related: Also learn balancing basic redox reactions as well as how to determine oxidation states.

Second law of thermodynamics Example

Let's make it easier for you. Suppose you have a separate room in the house which has not been cleaned for a long time. You will see that it would get more disordered and messier with time - even if no one uses it out. Thus, the mess and disorder are entropy of your isolated system. Also try to learn what are the chemical reaction and its types for better learning.

On cleaning the room, you shift this entropy outside the room(system) by which the value of entropy decreases in the system while it increases for the surroundings.

Third law of thermodynamics

The third law of thermodynamics states that:

"The entropy of a system is zero on absolute zero or when the temperature drops to absolute zero (0K)."

Mathematically, this 3rd law of thermodynamics is represented as follows

S - So = kblnΩ

In this equation, S is the entropy of the thermodynamic system; kb is the Boltzmann constant, Ω is the total microstates of the system, and So is the initial entropy.

You can also understand what is conversion factor in chemistry and for better learning.

This law describes the limiting behavior of a thermodynamic system (a perfect crystal) where the temperature is equal to absolute zero. Moreover, this law also illustrates that the relationship between the temperature and entropy of a system is directly proportional to each other.

Also know about importance of gas laws in daily life as well as learn how to balance a complex chemical equations.

Third law of thermodynamics Example

To understand this law more precisely, consider the example of water whose entropy is maximum above hundred degrees since, at that point, water is present in the form of vapors that move randomly and quickly to increase the degree of disorderliness (entropy).

As we decrease the temperature of the water below hundred degrees, these vapors start to condensed back into liquid form. In the liquid state, the movement of molecules decreases. Thus the degree of disorderliness (entropy) also gets reduced.

We hope this blog from equationbalancer is more than helping for you in learning of 3 laws of thermodynamics. Find our other amazing articles for the best and easy information for your difficult topics. Such as metal displacement reaction in an aqueous medium and what is a synthesis reaction.Happy Learning!