According to the first law of thermodynamics, energy cannot
be created or destroyed, although it can change from one form to another.
Examples of the first law of thermodynamics:-
1) A 1000 Watt electrical heater uses 1000 J/sec of
electrical energy. If it is 60%
efficient, then the heater converts 60% of the electrical energy into heating
water and 40% is wasted by being transformed into heat.
-Electric energy transformed into light and heat energy
-This is the law of the conservation of energy. It states
that energy can neither be created, nor can it be destroyed. This means that
the total amount of energy in the universe always remains conserved, or
constant. However, energy can be changed from one form to another.
2) When an exothermic reaction occurs some of the
molecular enthalpy (energy in the molecules) of the system is converted into
heat or light. This energy is then released by the system to the surroundings.
The total energy of the system decreases, but the energy of the surroundings
increases by the same amount.
Energy (system) = - Energy (surroundings)
3) The gasoline that you put in your automobile has
potential energy stored as chemical energy in its molecular bonds. As gasoline
is burned it releases energy, part of this energy is captured and transformed
into mechanical energy to move the car forward. The remainder of the energy is
lost as heat energy. The first law of thermodynamics explains how chemical
energy converts to mechanical energy.