Introduction to Chemistry

Definition of Chemistry:

Chemistry is a branch of science that deals with the study of matter, its structure, composition, properties, and the changes it undergoes. Other branches of science are biology and physics.

Branches of Chemistry:

The three main branches of Chemistry are Physical, Inorganic and Organic Chemistry.

1. Physical Chemistry:

• Deals with the physical principles that underlie chemical systems.
• Explains how matter behaves and why reactions occur.
• Uses concepts of physics and mathematics in chemistry.
• Examples: energyEnergy is the ability to do work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, and electrical energy. Units of Energy: The SI unit... More changes in reactions, reaction rates, equilibrium, and thermodynamics.

2. Inorganic Chemistry:

• Studies inorganic compounds (compounds that are not based mainly on carbon).
• Includes metals, salts, minerals, and industrial chemicals.
• Examples: acids, bases, salts, metals, coordination compounds.

3. Organic Chemistry:

• Studies carbon compounds, especially those containing hydrogen, oxygen, nitrogen, and other elements.
• Concerned with the chemistry of life and synthetic materials.
• Examples: fuels, plastics, alcohols, carbohydrates, proteins, and medicines.

The study of Chemistry enables us to acquire certain scientific skills such as handling Laboratory apparatus, performing experiments and thinking scientifically.

We experience chemical changes in our everyday life, e.g. cooking, lighting matches, burning firewood, rusting of nails, etc. 

Scientific Method:

The Scientific method deals with Law, theory and hypothesis. It is the process scientists use to investigate problems and explain natural events. It involves observation, experiment, and reasoning.

Three important outcomes of the scientific method are:

• Hypothesis
• Theory
• Law

Hypothesis and Theory:

A theory is an idea suggested to explain an experimental fact. For example, the compressibility of gases is explained by the Kinetic Theory of Matter, which assumes that gases are made up of tiny particles that are far apart.

When an idea is still being tested, it is called a hypothesis.

Scientists use their senses to observe what happens around them. These observations help them identify a problem they want to solve. A hypothesis (a reasonable explanation) is then put forward, and an experiment is carried out.

• If the hypothesis is tested and found correct, it can become a theory (e.g. Atomic Theory).
• When a theory is repeatedly tested and always proven true, it becomes a law (e.g. Boyle’s Law, Newton’s Laws of Motion, Ohm’s Law).

If the experiment produces negative results, the scientist goes back to the hypothesis, makes changes, and tries again until a better explanation is found.

A Scientific Law:

A scientific law is a statement that describes natural facts or patterns in nature that have been repeatedly confirmed by experiments.

For example, experiments have shown that all gases are compressible.

Scientific laws:

• Are based on repeated observations and experiments.
• Describe what happens in nature, not why it happens.
• Are universally accepted as true under the conditions tested.