Introduction to General Chemistry: Matter, Measurement, and Basic Calculations

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Introduction to General Chemistry

Classification of Matter

Matter is anything that occupies space and has mass. It can be classified based on its composition and properties.

Pure Substances: Consist of only one type of particle. They can be elements (single type of atom) or compounds (two or more elements chemically bonded).
Mixtures: Combinations of two or more substances that are not chemically bonded. Mixtures can be:
- Homogeneous Mixtures (Solutions): Uniform composition throughout (e.g., salt water).
- Homogeneous Mixtures (Solutions): Uniform composition throughout (e.g., salt water).
- Heterogeneous Mixtures: Non-uniform composition (e.g., salad, sand and iron filings).

Example: Classify the following: Glucose (pure substance), Crystalline sugar (pure substance), Lead wire (element), Salsa (heterogeneous mixture).

Physical and Chemical Changes

Changes in matter can be classified as physical or chemical:

Physical Changes: Changes in the state or appearance of matter without altering its composition (e.g., melting, dissolving sugar in water).
Chemical Changes: Changes that result in the formation of new substances with different properties (e.g., burning wood, rusting iron).

Example: Dissolving sugar in water is a physical change; burning wood is a chemical change.

Reversible and Irreversible Changes

Reversible Changes: Can be undone, such as phase changes (melting, freezing, boiling).
Irreversible Changes: Cannot be undone, such as burning or rusting.

Example: Melting ice is reversible; burning paper is irreversible.

Chemical and Physical Properties

Chemical Properties: Observed during a chemical reaction (e.g., flammability, reactivity with acids).
Physical Properties: Can be measured without changing the substance's identity (e.g., color, melting point, density).

Example: Mercury is a silvery liquid at 25°C (physical property); sodium reacts violently with water (chemical property).

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).

Example: Density is intensive; mass is extensive.

Temperature and Heat

Thermal Energy: The sum of kinetic and potential energies of all atoms in an object.
Temperature: The average kinetic energy of particles in a substance.

Temperature Conversion Formulas:

Celsius to Kelvin:
Celsius to Fahrenheit:

Scientific Notation

Scientific notation is used to express very large or small numbers in the form .

Coefficient: A number between 1 and 10.
Exponent: Indicates the power of 10.

Example:

SI Units and Measurements

The International System of Units (SI) is the standard for scientific measurements.

Physical Quantity	Name	Symbol
Length	meter	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Amount of substance	mole	mol

Metric Prefixes

Metric prefixes indicate multiples or fractions of base units.

Prefix	Symbol	Multiplier
kilo	k
centi	c
milli	m
micro	μ
nano	n

Significant Figures

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

All nonzero digits are significant.
Zeros between nonzero digits are significant.
Leading zeros are not significant.
Trailing zeros are significant only if there is a decimal point.

Example: 0.00364 has 3 significant figures.

Precision in Measurements

When recording measurements, include all certain digits plus one uncertain digit (the last digit).

Significant Figures in Calculations

Multiplication/Division: The result should have as many significant figures as the value with the fewest significant figures.
Addition/Subtraction: The result should have as many decimal places as the value with the fewest decimal places.

Conversion Factors

Conversion factors are ratios used to convert between units.

Example:
Common conversion factors involve length, mass, and volume.

Dimensional Analysis

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

Set up the problem so that units cancel appropriately.
Multiply by conversion factors until the desired unit is obtained.

Density

Density is the amount of mass per unit volume.

Formula:

For solids and liquids, units are typically g/cm3 or kg/m3.
For gases, units are often g/L.

Density of Geometric and Non-Geometric Objects

For regular shapes, use geometric formulas for volume (e.g., for a cube).
For irregular shapes, use water displacement to determine volume.

Example: If a cube of silver (density 10.5 g/cm3) measures 3.60 cm on each side, its mass is .

Additional info: These notes cover foundational concepts from "Ch.1 - Introduction: Matter, Energy, and Measurement" and "BONUS: Mathematical Operations and Functions" in a General Chemistry course, including classification of matter, properties, measurement, and basic calculations.