Law of Conservation of Mass

The law of conservation of mass holds great importance in physics and chemistry. Only because of this law scientists are able to understand and interpret the chemical reactions more thoroughly. But, there is a lot of confusion and misinterpretations regarding this law. 

If you also have a lot of questions regarding the law then this article is for you. In this article, we will define the law of conservation of mass with examples and explain its formula and importance  without any technical jargon.

What is the Law of Conservation of Mass?

The law of conservation of mass states that for any closed system, matter cannot be created or destroyed but can be transformed from one form to another. In the context of chemistry, this law says that the mass of the products equals the mass of the reactants in any chemical reaction. 

Now, you may ask what is a closed system? Great question! A closed system or isolated system is one where the transfer of matter in or out of the system is not allowed. Due to this, the mass which is present in that isolated system will remain constant, regardless of any chemical reaction that occurs. You may get a result that is different from what you had in the beginning. Although there won’t be any more or less mass than what you had at the start of the chemical reaction.

The law of conservation of mass helped the scientists understand that the substances present in the chemical reaction don’t just disappear (as they may appear to do). Instead, they get transformed into another substance of equal mass. This concept of conservation of mass is widely used in chemistry, mechanics, and fluid dynamics. 

The concept of conservation of mass was first founded by Mikhail Lomonosov. Later, in the late 18th century the study of conservation of mass was taken further by Antoine Lavoisier. The formulation of this law took chemistry to the next level. Although this law had to be modified to comply with the laws of quantum mechanics and special relativity.

This law does not hold for nuclear reactions. According to the law, matter cannot be created or destroyed but, in nuclear reactions, the mass is transformed into energy. 

Formula of Law of Conservation of Mass:

The formula of the law of conservation of mass can be expressed mathematically in the differential form in the fields of fluid mechanics and continuum mechanics using the continuity equation as follows:

∂p/∂t + ▽ (pv) = 0

Where,

p is the density

t is the time

v is the velocity

▽ is the divergence

Examples of Law of Conservation of Mass:

Let’s understand the law of conservation of mass with some examples. 

Combustion Process:

One of the most common examples is the bonfire or campfire ones. Imagine that you and your family have gone on a trip in the jungle. At night you gather some sticks and light them with a match. After a certain period, you notice that the campfire you had built has turned into ashes and some smoke. Now, you might think that the original mass of the sticks has vanished into ashes. But, this is not true. Instead, it has just transformed.

In this case, the sticks that you burned combined with the oxygen in the air and turned into ash, carbon dioxide and water vapor. So, if we measure the mass of the sticks and oxygen before setting the sticks on fire, you will find that this mass is equal to the mass of ashes, water vapour and carbon dioxide combined.

Similarly, when you light a candle that is made from wax and a wick, after some time some of the wax turns into gasses: water vapour and carbon dioxide. The mass before lighting the candle after burning it is the same.

Chemical Reactions:

Water is composed of two hydrogen atoms and one oxygen atom. As we all know water exists in three states: solid, liquid, and gas. To go amongst these three states water must undergo some physical changes. The number of water molecules before and after turning into ice remains chemically the same.

Both oxygen and hydrogen are diatomic atoms. This means that they are present naturally as bonded pairs (H2 and O2). In the precise conditions and with the help of adequate energy these diatomic bonds will break. The atoms that are now present individually will combine to form H2O (water).

As you can see, water is an excellent example of how the cycle of matter works. Things don’t just vanish but transform into a new substance.

Conclusion:

The law of conservation of mass is not at all a complex concept. You just need to remember that the matter cannot be created or destroyed but can be transformed from one form to another. It’s magical to see that substances that we might think have vanished don’t vanish and remain in the environment in some different form. We hope that this article helped you to understand the meaning and significance of this law without any complications.