Give some examples of law of conservation of mass in our daily life

The following examples in our daily life shows the validity of law of conservation of

mass.

(i)          In the heating of coal, the weight of remains ash is far less than the actual weight of coal. But this is apparent change in weight. If we weight the combining oxygen and the carbon before burning, and weigh the ash and carbon dioxide after burning, then in both cases the mass is same. Thus the total mass of reactants and the total mass of product remains constant.

(ii)        Rusting of iron: When a piece of iron is placed in open air, a red layer of rust is formed. The mass of the iron piece increases. Rusting is the slow conservation of iron into its hydrated oxide in the presence of moisture and air.

               4Fe +3O₂ =2Fe ₂O₃

                                    Fe ₂O₃ +H₂O = Fe ₂O₃ x H₂O

Where  ‘x’ is any positive whole number. If we weigh the mass of iron, oxygen and water placed in a jar before rusting and after rusting the mass remains constant. Thus the law of conservation of mass valid in rusting of iron.                                                                                                                                                                                   

Energy : The capacity to do work is called energy.

Explaination : Energy is stored up work. A body is said to possess energy when it is capable of doing work. Thus, energy is measured by the total quantity of work that a body or a system of bodies can do.

Heat, sound, light, electricity are the examples of energy. Energy neither have volume nor contains mass and it also does not occupy any space. That is energy is not a matter but it is the capacity of doing work. We cannot see energy but can feel its existence like light ,we cannot see light but we can feel its existence when light falls on something , exactly like light we cannot see heat but can feel it.

Energy is a scalar quantity. It is measured by the amount of work that the body can do.

Unit: The CGS unit of energy is erg, SI unit is Joule ( J) and the bigger unit of energy are watt hour (Wh) and kilowatt hour(Kwh).   

Different forms of energy: The following are the various forms of energy.

Mechanical energy, Heat energy, Light energy, Sound energy, Electric energy, Magnetic energy, Chemical energy, Nuclear energy ( or Atomic energy)**