Introductory Chemistry
(Lecture Note)
Chemistry is a science that studies the composition and properties of matter.
 Matter is anything that takes up space and has mass
 Mass is a measure of the amount of matter in a sample
 Chemistry holds a unique place among the sciences because all things are
composed of chemicals
 A knowledge of chemistry will be valuable whatever branch of science you study
 Characteristics or properties of materials distinguish one type of substance from
another
 Properties can be classified as physical or chemical
 Physical properties can be observed and measured without changing the
chemical identity of the substance, such as melting point, color, density,
odor...
 Chemical properties involve a chemical change and result in different
substances, such as flammability
EVOLUTION OF CHEMISTRY
The earliest concept of science began with ancient Chinese, Egyptian and Greek
civilization. The Chinese believed that the universe was created from the interaction of
two forces, namely YIN and YANG. Yin, the feminine force, was manifested in
darkness, cold and wetness. Yang, the masculine force, was manifested in light, heat and
dryness. They believed that these two forces interacted and brought about the material
world into existence.
The Greek on the other hand, proposed that the AIR, FIRE, EARTH, WATER (Thales,
founder of Greek science) were the four elements that make up the universe.
EKIBOLAJI Page 1 6/30/2016
These elements were associated with the following properties- hot, cold, wet and dry.
The fifth is ether.
SCIENTIFIC METHOD
Robert Boyle, in one of his books, stated that scientific speculation was worthless unless
supported by experimental evidence. This led to the development of scientific method
which marked a turning point and the beginning of modern science.
What is Science?
Science is a method of exploring nature followed by a logical explanation of the
observation. The practice of science entails the following:




Planning an investigation
Carefully recording observation
Gathering data
Analyzing the results
These four steps are the processes involved in an experiment, and this leads us to the
definition of experiment.
An experiment is exploring nature according to a planned strategy and makes
observations under controlled conditions.
What is Scientific Method?
This is the systematic investigation of nature and requires proposing an explanation for
the results of an experiment in the form of a general principle.
What is a Hypothesis?
Hypothesis is the initial, tentative proposal of a scientific principle. After further
experimentation on the hypothesis, it may be Rejected, Modified or elevated to the status
of scientific principle. A hypothesis can only become a scientific theory when backed up
with sufficient evidence. A scientific theory is not accepted until rigorous testing has
established that the hypothesis a valid interpretation of the evidence. A good example is
John Dalton that proposed that all matter was composed of small indivisible particles
called atoms.
EKIBOLAJI Page 2 6/30/2016
However, it took 100 years of gathering additional evidence before his proposal was
universally accepted and elevated to the status of the Atomic Theory.
What is ‘Theory’ and ‘Natural Law’?
A theory is a model that explains behavior nature, while Natural Law states measurable
relationship. For example, Law illustrates that heat flows from hotter objects to cooler
one, because we can measure experimentally the change in temperature if we drop an ice
cube into water. On the other hand, it is a theory that the heat transfer is due to changes in
the motion of molecules in the ice and water. We can distinguish between theory and
natural law by simply asking the question: Is the proposal measurable? If yes, then it is a
Law otherwise, it is a theory.
MODERN CHEMISTRY
The Arabs introduced the Pseudoscience of Alchemy (pseudo means false). Alchemy is
the existence of a magic portion that had miraculous healing powers and could transmute
lead into gold. This did not withstand the test time; it preceded the planned, systematic
scientific experiments that are the cornerstone of modern chemical research.
By now we all know that, CHEMISTRY studies the COMPOSITION of Matter and its
PROPERTIES. The advancement in Chemistry led to the division of the subject into
various branches and specialties.

ORGANIC CHEMISTRY- Is a branch of chemistry that studies substances
containing Carbon.

INORGANIC CHEMISTRY- Is a branch of chemistry that studies
substances that do not contain carbon.

BIOCHEMISTRY- Is a branch of chemistry that studies substances derived
from plants and animals
EKIBOLAJI Page 3 6/30/2016

PHYSICAL CHEMISTRY- Is a specialty that proposes theoretical and
mathematical explanation for chemical behavior.

ANALYTICAL CHEMISTRY- Is a branch of chemistry that studies
Quantitative Analysis (how much of each substance is present) and the
Qualitative Analysis (What substance are in a sample).

ENVIRONMENTAL CHEMISTRY- Is a branch of chemistry that studies
the safe disposal of chemical waste.
Chemistry plays important roles in the following fields:
Medicine- Pharmaceutical prescription.
Agriculture- formulating fertilizers and pesticides.
Industries- Automobile, electronic components, Aluminum steel, paper and plastic.
Petrochemical- (these are chemicals derived from petroleum and natural gas) these
chemicals are used in the making of paints, plastics, rubber, textiles, dyes, detergents,
explosives and so on.
EKIBOLAJI Page 4 6/30/2016