Intro to General Chemistry

Classification of Matter

Chemistry is the study of matter and the changes it undergoes, with matter 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 only 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.

Examples: Gatorade (mixture), Crystalline sugar (compound), Lead wire (element), and Salsa (mixture).

Classification Table

Homogeneous Mixture: Uniform composition throughout (e.g., air, saline solution). Substance: Pure form of matter (element or compound).

Physical and Chemical Changes

Changes in matter can be classified as physical or chemical:

• Physical Change: Changes in the physical state of a substance without a change in composition (e.g., melting ice, dissolving sugar in water).

• Chemical Change: Changes in chemical composition that create new chemical bonds and products (e.g., iron rusting, burning wood).

Reversible Change: Can be reversed to restore the original structure (e.g., phase changes like melting/freezing). Irreversible Change: Permanent and cannot be undone (e.g., burning paper).

Properties of Matter

• Chemical Property: Observed during a chemical reaction (e.g., flammability, reactivity with acids).

• Physical Property: Can be measured or observed without changing the chemical structure (e.g., density, color, melting point).

Intensive vs. Extensive Properties

• Intensive Properties: Do not depend on the amount of substance (e.g., density, boiling point, color).

• Extensive Properties: Depend on the amount of substance (e.g., mass, volume, energy).

Temperature and Heat

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

• Temperature: The average kinetic energy of an object.

• Heat: The flow of thermal energy from an object at higher temperature to one at lower temperature.

Temperature Conversions:

Scientific Notation

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

• Format: where is the coefficient and is the exponent.

• Moving the decimal to the left increases the exponent; to the right decreases it.

SI Units and Measurements

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

Formulas:

• Perimeter:

• Area (rectangle):

• Volume (rectangular prism):

Metric Prefixes

• Metric prefixes are modifiers that are multiples of ten (e.g., kilo-, centi-, milli-).

• They are used to express measurements in different scales.

Significant Figures

• Significant figures are the digits in a measurement that are known with certainty plus one estimated digit.

• Rules for significant figures include:

  • All nonzero digits are significant.

  • Zeros between significant digits are significant.

  • Leading zeros are not significant.

  • Trailing zeros in a decimal number are significant.

When multiplying/dividing: The result should have the same number of significant figures as the measurement with the fewest significant figures. When adding/subtracting: The result should have the same number of decimal places as the measurement with the fewest decimal places.

Conversion Factors and Dimensional Analysis

• A conversion factor is a ratio that expresses how many of one unit are equal to another unit.

• Dimensional analysis is a systematic approach to problem-solving that uses conversion factors to move from one unit to another.

Example: To convert 32 inches to centimeters, use the conversion factor .

Density

• Density expresses the amount of mass per unit volume of a substance.

Formula:

Units for solids and liquids are typically g/cm3 or g/mL; for gases, kg/m3 or g/L.

Density of Geometric and Non-Geometric Objects

• For geometric objects, use volume formulas (e.g., for a sphere: ).

• For irregular objects, use water displacement to determine volume.

Example: If a cube of silver (density = 10.5 g/cm3) measures 0.5 cm on each side, its mass is .

Summary Table: Key Concepts

Additional info: These notes cover foundational concepts in general chemistry, including matter classification, properties, measurement, and basic calculations, suitable for exam preparation and introductory coursework.