Chapter 1 – Introduction to Chemistry
(Lecture Notes)
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
o Physical properties can be observed and measured without changing the
chemical identity of the substance, such as melting point, color, density,
odor...
o Chemical properties involve a chemical change and result in different
substances, such as flammability
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
observations. The practice of science entails the following:

Planning an investigation

Carefully recording observations

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 making
observations under controlled conditions.
What is the 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 is 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.
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 a behavior in nature, while a Natural Law states
measurable relationships. For example, the statement “heat flows from a hotter object to
a cooler one” is labeled as natural law, because we can measure experimentally the
change in temperature when 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
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 based on
carbon.

INORGANIC CHEMISTRY- Is a branch of chemistry that studies substances other
than those based on carbon.

BIOCHEMISTRY- Is a branch of chemistry that studies substances derived from
plants and animals

PHYSICAL CHEMISTRY- Is a specialty that proposes theoretical and mathematical
explanations for chemical behavior.

ANALYTICAL CHEMISTRY- Is a branch of chemistry that studies Quantitative and
Qualitative Analysis (how much of each substance is present, or what substances
make up a sample).

ENVIRONMENTAL CHEMISTRY- Is a branch of chemistry that studies the safe
disposal of chemical waste.
Chemistry plays important roles in many fields, including:

Medicine- pharmaceuticals, medical supplies, imagery (X-rays, MRI).

Agriculture- formulating fertilizers and pesticides.

Industries- Automobile, electronic components, steel, paper and plastics.

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, etc.