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Study Guide - Smart Notes

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Introduction to General Chemistry

Classification of Matter

Matter is anything that occupies space and has mass. Chemistry is the study of matter and the changes it undergoes, with the atom being its basic functional unit. Matter can be classified into different types based on its composition and properties.

  • Pure Substances: Consist of only one type of particle and have a fixed composition. Examples include elements and compounds.

  • Mixtures: Composed of two or more substances physically combined. Mixtures can be homogeneous (uniform composition, e.g., salt water) or heterogeneous (non-uniform composition, e.g., salad).

Example: Crystalline sugar is a pure substance; salsa is a heterogeneous mixture.

Type

Description

Example

Element

Cannot be broken down by chemical means

Compound

Composed of two or more elements chemically combined

Water (H2O)

Homogeneous Mixture

Uniform composition throughout

Salt water

Heterogeneous Mixture

Non-uniform composition

Salad

Physical and Chemical Changes

Physical Changes

Physical changes alter the physical state of a substance without changing its chemical composition.

  • Examples: Melting, boiling, dissolving sugar in water.

Chemical Changes

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

  • Examples: Burning wood, cooking an egg, rusting iron.

Reversible and Irreversible Changes

  • Reversible Changes: Can be undone (e.g., melting and freezing water).

  • Irreversible Changes: Cannot be undone (e.g., burning paper).

Chemical and Physical Properties

Chemical Properties

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

  • Examples: Reactivity with acids, flammability, oxidation.

Physical Properties

Physical properties can be observed or measured without changing the substance's chemical identity.

  • Examples: Color, melting point, density, state of matter.

Intensive vs. Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present.

  • Examples: Density, melting point, temperature.

Extensive Properties

Extensive properties depend on the size or amount of substance present.

  • Examples: Mass, volume, length.

SI Units and Measurements

SI Base Units

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

Physical Quantity

Name

Symbol

Length

meter

m

Mass

kilogram

kg

Time

second

s

Temperature

kelvin

K

Amount of substance

mole

mol

Electric current

ampere

A

Luminous intensity

candela

cd

Perimeter, Area, and Volume

  • Perimeter: Sum of the lengths of the sides of a shape.

  • Area: for rectangles.

  • Volume: for rectangular solids.

Metric Prefixes

Metric Prefix Multipliers

Metric prefixes are used to express multiples or fractions of base units.

Prefix

Symbol

Multiplier

kilo

k

centi

c

milli

m

micro

μ

nano

n

Temperature

Thermal Energy and Temperature

Thermal energy is the sum of kinetic and potential energies of all atoms in an object. Temperature measures the average kinetic energy of particles.

  • Temperature Conversion:

Scientific Notation

Format for Scientific Notation

Scientific notation expresses very large or small numbers in the form .

  • Example:

Conversion Between Standard and Scientific Notation

  • Move the decimal point to create a coefficient between 1 and 10, adjusting the exponent accordingly.

Significant Figures

Identifying Significant Figures

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

  • Rules:

    • All nonzero digits are significant.

    • Zeros between nonzero digits are significant.

    • Leading zeros are not significant.

    • Trailing zeros in a decimal number are significant.

Significant Figures in Calculations

  • Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

  • Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

Conversion Factors and Dimensional Analysis

Conversion Factors

Conversion factors are ratios used to express a quantity in different units.

  • Example:

Dimensional Analysis

Dimensional analysis is a method for converting between units using conversion factors.

  • Set up the calculation so that units cancel appropriately, leaving the desired unit.

Density

Density Formula

Density is the amount of mass per unit volume.

  • Formula:

  • Units: g/cm3 for solids and liquids, g/L for gases.

Density of Geometric and Non-Geometric Objects

  • For regular shapes, calculate volume using geometric formulas.

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

Example: If a cube has a side length of 0.36 m and the density of silver is 10.5 g/cm3, calculate its mass.

Additional info: Water displacement is a common laboratory technique for measuring the volume of irregular solids.

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