Question

State and explain the law of conservation of mass.

Answer 1

- Hint: As the name suggests, the law deals with the conservation of mass when a substance undergoes a physical or chemical change.


Complete step-by-step solution -

The law of conservation of mass states that, in a system which is closed for the transfer of energy and matter, the mass must remain constant the entire time. In other words, “mass neither be created nor be destroyed but it can be transferred from one form to another”. Let us understand more about this law.
This law stands for any physical or chemical changes that take place in a closed system. When we consider a chemical reaction, the combined mass of all the reactants participating in the reaction must be equal to the combined mass of all the products that are formed at the end of the reaction.
We must keep in mind that we use an open system, i.e., a system which allows energy or matter to escape, the law of conservation of mass will not hold. That means the mass of the system will not be constant throughout the process or reaction.
This is because in many chemical reactions gases are produced at the end of the reaction. If we keep the system open, some of the gases may escape from the system and their masses will not be accounted for while calculating the entire mass before and after the reaction.

Note: Always remember that the entire system should be closed and any amount of energy and matter should not escape from the system. If energy and matter escape from the system, they should be taken into consideration before calculating the mass of the system. Then only the law will apply to the system.