Law of conservation of energy states that, the total amount of energy in an isolated system remains constant over time. It says that energy can neither be created nor be destroyed but can only be transferred from oneform to another (isolated system implies a closed system which does notinteract with its surroundings).
As an example we can state, conversion of mechanical energy to electrical energy in a generator.
Indaily life we can observe another simpler example. When you switch on an electrical heater, electrical energy is converted to heat energy. In other words, the measured electric energy is equal to heat energy produced. Similar to this example, electrical energy may be converted into other forms like heat energy, magnetic energy, kinetic energy too.
Law of conservation of energy is also called First law of Thermo dynamics
Law of conservation of Mass
Lawof conservation of Mass states that, the mass in a closed or isolated system remains the same over time. Which implies, mass can neither be destroyed nor be created, but can be rearranged in space and changed into different particles.
Inbrief it says, for any chemical process in a closed or isolated system the mass of the reactants must equal to the mass of products.
Inchemical terms, the chemical combination of Iron and Sulphide results in Iron sulphide. If you measure mass of Iron and Sulphur individually before and combined after the chemical reaction it remains the same.
Inother terms, when copper metal is heated in air and weighed the resulted mass is increased. While heating in the air, it comes together to oxygen in air. So if the mass of oxygen is taken into account then the sum of masses of oxygen gets equaled before and after the heating process. It clearly shows no detectable increase or decrease of quantityof matter. This behavior is called Law of conservation of Mass.