Introduction to General Chemistry

What is Chemistry?

Chemistry is the scientific study of matter, its properties, composition, and the changes it undergoes. It is a foundational science that explores the substances that make up the universe and the interactions between them.

• Matter: Anything that has mass and occupies space.

• Atom: The basic unit of matter, consisting of a nucleus surrounded by electrons.

Atoms & Elements

Elements and Compounds

Understanding the difference between elements and compounds is essential in chemistry. Elements are pure substances, while compounds are combinations of elements.

• Element: A pure substance made of only one kind of atom (e.g., O2, Fe).

• Compound: A substance made of two or more different elements chemically bonded together (e.g., H2O, NaCl).

Chemical Reactions

Physical and Chemical Changes

Chemical and physical changes describe how matter transforms or remains the same under different conditions.

• Physical Change: A change that does not alter the chemical composition of a substance (e.g., melting ice).

• Chemical Change: A process that results in the formation of new substances with different properties (e.g., burning wood).

Chemical Quantities & Properties

Properties of Matter

Matter can be described using various properties, which are classified as either extensive or intensive.

• Mass and Volume: Extensive properties that depend on the amount of substance present.

• Intensive Properties: Properties that do not depend on the amount of substance (e.g., density).

Classification of Matter

Pure Substances and Mixtures

Matter can be classified based on its composition as either pure substances or mixtures.

• Pure Substances: Have a fixed composition. Examples include elements and compounds.

• Mixtures: Combinations of two or more substances that can be separated by physical means (e.g., salt water).