Chemistry and Classification of Matter

Definition and Types of Matter

Chemistry is the study of matter and the changes it undergoes, with the atom being its basic functional unit. Matter is anything that occupies space and has mass. Matter can be classified into three main types:

• Element: The simplest type of matter, composed of one kind of atom.

• Compound: Matter composed of two or more different elements that are chemically bonded together.

• Mixture: Matter composed of elements and/or compounds that are physically mixed together but not chemically bonded.

Classification Table

Example: Crystalline sugar and lead wire are pure substances; salsa is a homogeneous mixture.

Mixtures: Homogeneous vs. Heterogeneous

• Homogeneous Mixture: Uniform composition throughout (e.g., black coffee, seawater).

• Heterogeneous Mixture: Non-uniform composition (e.g., chicken noodle soup, trail mix).

Physical and Chemical Changes

Physical Changes

Physical changes alter the state or appearance of matter without changing its chemical composition. Examples include melting, dissolving, and phase transitions.

• Examples: Dissolving sugar in water, melting wax.

Chemical Changes

Chemical changes result in the formation of new substances with different chemical properties. These involve breaking and forming chemical bonds.

• Examples: Iron rusting, cooking an egg, burning wood.

Reversible and Irreversible Changes

Reversible Changes

Reversible changes can be undone to restore the original structure, such as phase changes (melting, freezing, boiling).

• Example: Dissolving sugar in water (can be reversed by evaporation).

Irreversible Changes

Irreversible changes cannot be undone, such as chemical reactions that produce new substances.

• Example: Baking a cake, burning wood.

Chemical and Physical Properties

Chemical Properties

Chemical properties describe how a substance reacts with other substances, resulting in a change in chemical composition.

• Examples: Reactivity with acids, flammability, oxidation.

Physical Properties

Physical properties can be observed or measured without changing the chemical identity of a substance.

• Examples: Color, density, melting point, boiling point.

Intensive and Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present. They are characteristic of the material itself.

• Examples: Density, melting point, temperature, luster.

Extensive Properties

Extensive properties depend on the amount of substance present.

• Examples: Mass, volume, energy.

SI Base Units and Measurements

SI Base Units

The International System of Units (SI) is based on seven base units:

Measurements: Perimeter, Area, Volume

• Perimeter: Total length around an object.

• Area: Measured in square units (e.g., ).

• Volume: Space occupied by an object (e.g., ).

Metric Prefixes and Scientific Notation

Metric Prefixes

Metric prefixes are modifiers that represent multiples of base units.

Scientific Notation

Scientific notation expresses numbers as a product of a coefficient and a power of ten, e.g., .

Temperature and Heat

Thermal Energy vs. Temperature

• Thermal Energy: The sum of kinetic and potential energies of all atoms in an object.

• Temperature: The average kinetic energy of the particles in a substance.

• Heat: The flow of thermal energy from a higher temperature object to a lower temperature object.

Temperature Conversions

• Temperature can be measured in degrees Celsius (C), Fahrenheit ($^ ext{o}$F), and Kelvin (K).

Summary Table: Properties and Changes

Additional info: These notes cover foundational chemistry concepts relevant for general chemistry, but do not directly address organic chemistry topics such as covalent bonding, molecular orbital theory, acid-base chemistry, reaction energy, or reaction rates.