Law of Conservation of Matter and Energy
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When a piece of copper metal is heated in air, it comes together with
oxygen in the air. Then if it is weighed, it is found to have a
greater mass that the original piece of metal. If however the mass of
the oxygen of the air that combines with the metal is taken into
consideration, it can be shown that the mass of the product is within the
limits of accuracy of any weighing instrument, equal to the sum of the
masses of the copper and oxygen that combine. This behavior of matter is
in accord with what is called the Law of Conservation of Matter:
During an ordinary chemical change, there is no detectable increase or
decrease in the quantity of matter.
Conversion of one type of matter into another are always accompanied by
the conversion of one form of energy into another. Usually heat is
leveled or absorbed, but sometimes the conversion involves light or
electrical energy instead of, or in addition to heat. Many
transformations of energy, of course, do not involve chemical changes.
Electrical energy can be changed into either mechanical, light, heat or
potential energy without chemical changes. Mechanical energy is
converted into electrical energy in a generator. Potential and kinetic
energy can be converted into one another. Many other conversions are
possible, but all of the energy involved in any change always appears in
some form after the change is completed.
The Law of Conservation of Energy states that energy cannot be created
or destroyed, but can change its form.
The total quantity of matter and energy available in the universe is a
fixed amount and never any more or less.