Introduction :
The law of conservation of mass is a fundamental principle in physics and chemistry which states that in any closed system, the mass of the system remains constant over time. In other words, the total amount of mass in a closed system before and after a physical or chemical change remains the same.
It is important to note that the law of conservation of mass applies only to closed systems, where there is no exchange of matter with the surrounding environment. In open systems, mass can be lost or gained through interactions with the environment, and the law of conservation of mass does not apply
What is Law of Conservation of Mass
∂ρ/∂t +⛛(ρv) = 0
Physical Change in Law of Conservation of Mass
In the Law of Conservation of Mass, a physical change is a process in which the properties of a substance change without any change in its chemical composition. In a physical change, the total mass of the substance remains the same before and after the change, since there is no change in the number of atoms or molecules involved
Example:
Examples of physical changes include changes in state, such as melting, freezing, boiling, and condensation, as well as changes in shape, size, or volume. For instance, when an ice cube melts, it undergoes a physical change from a solid to a liquid state, but the total mass of the water remains the same.
Chemical Change in Law of Conservation of Mass
NaOH + HCl → NaCl + H2O
Reactants:
Products:
Combustion Process
Combustion is a chemical reaction that occurs when a fuel combines with oxygen to produce heat and light. The combustion process involves a series of steps that can be summarized as follows:
The combustion process can be illustrated using the example of burning gasoline in an internal combustion engine:
Law of Conservation of Mass Examples
Example:
CH4 + 2O2 → CO2 + 2H2O
Calculate the moles of methane and oxygen:
Moles of CH4 = 16 g
Moles of O2 = 64 g
the total mass of reactants was: 16 + 64 = 80 g
44 + mass of H2O = 80 g
we get the mass of 2 moles of H2O as 36 g.