Matter and Its Classification

Definition of Chemistry and 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.

• Pure Substance: Composed of only one kind of atom or molecule.

• Compound: 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.

Classification of Matter

Matter can be classified based on its composition:

Homogeneous Mixture: Uniform composition throughout (e.g., salt water). Heterogeneous Mixture: Non-uniform composition (e.g., trail mix).

Example

Classify the following: Gatorade, Crystalline sugar, Lead wire, Salsa. Gatorade and Salsa are mixtures; Crystalline sugar and Lead wire are pure substances.

Physical and Chemical Changes

Physical Changes

Physical changes alter the state or appearance of matter without changing its composition.

• Examples: Dissolving sugar in water, melting, boiling, freezing.

• No new substances are formed.

Example

Which is a physical change? Dissolving sugar in water

Chemical Changes

Chemical changes result in the formation of new substances with different properties.

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

• Involves breaking and forming chemical bonds.

Example

Which is a chemical change? Cooking an egg

Reversible and Irreversible Changes

Reversible Changes

These changes can be undone, restoring the original structure (e.g., phase changes).

• Examples: Melting and freezing, dissolving compounds in liquids.

Irreversible Changes

These changes cannot be undone; the original structure cannot be restored (e.g., chemical reactions).

• Examples: Burning, rusting.

Phase Changes Table

Chemical and Physical Properties

Chemical Properties

Properties observed during a chemical reaction; describe how a substance reacts.

• Examples: Reactivity with acids, flammability, oxidation.

Example

Which is not a chemical property? It has a yellow-orange color

Physical Properties

Measurable properties that describe the state of a chemical compound without changing its chemical structure.

• Examples: Density, melting point, color, boiling point.

Example

Which is a physical property? Mercury is a silvery liquid at 25°C

Intensive and Extensive Properties

Intensive Properties

Properties that do not depend on the amount of substance present.

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

Example

Which are intensive properties? Melting point, luster

Extensive Properties

Properties that depend on the amount of substance present.

• Examples: Mass, volume, energy.

Example

Which is an extensive property? Chemical energy

Temperature and Heat

Thermal Energy vs. Heat

Thermal Energy is the sum of kinetic and potential energies of all atoms in an object. Temperature is the average kinetic energy of an object. Heat is 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 (°F), and Kelvin (K).

Scientific Notation

Format for Scientific Notation

Used to express very large or small numbers in a compact form.

• Coefficient: Number between 1 and 10.

• Base: Always 10.

• Exponent: Indicates the number of decimal places moved.

Example

Standard Notation to Scientific Notation

• Move the decimal to create a coefficient between 1 and 10.

• Count the number of places moved for the exponent.

SI Base Units and Measurements

SI Base Units

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

Perimeter, Area, and Volume

• Perimeter: Distance around an object.

• Area: Measure of surface.

• Volume: Space occupied by a 3D object.

Additional info:

• Practice questions throughout the notes reinforce understanding of classification, properties, and measurement in chemistry.

• Tables and diagrams are used to compare and classify types of matter, changes, and properties.