Introduction:
Matter often undergo marked and
permanent changes under certain conditions. Milk may become
sour; bright Copper might become dull and ultimately get covered
with a green film , when exposed to moist air; iron too rust away
into a brown powder in moist air. A candle buns away and apparently
disappears.
In other cases the changes are less
marked, and the properties of the materials are only modified
temporarily. For example water freezes to ice during winter and when
spring and summer sets the frozen water melts to give the same old
liquid water. Iron becomes red hot on heating and comes back to its
old status on cooling.
Some changes occur with the absorption
of heat energy (Endothermic) and a few may release heat energy(
Exothermic).
Plants produce food when sun light
falls on their leaves using water and carbon dioxide ( Photo
chemical reaction). When copper plate and zinc plate are kept in
dilute sulphuric acid electricity is produced ( Electro chemical
reaction)
All these changes that occur in nature
are grouped under Chemical changes and take us into the amazing
world of chemistry.
Chemistry involves a systematic study
of the substances in the Universe, of their properties and their
reactions with each other to form new substances with different
properties, and of the conditions governing those chemical
reactions.
If the above is true then Chemistry
would have been a little more than a massive catalogue of facts and
recipes and a collection of techniques to discover
them.
Chemistry is also concerned with
classifying the data it has acquired and where ever possible
condensing them into a series of PRECISE GENERALIZATIONS CALLED LAWS
.
These Laws are statements that
summarize in an ideal form the results of a large number of separate
experiments or observations.
A law can be verified by performing
experiments and showing that the results conform to the law within
the known limits of experimental error. Since the law holds true for
all investigated cases, it is assumed to be a reliable guide to case
not yet investigated experimentally, at least until evidence to the
contrary (disobeying the law) is obtained.
It should be noted that the Laws of
science are not like a counties laws or laws of a game; the
laws of science are summaries of what has always been found to
happen in NATURE whether they suit human interest or
not.
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