General Chemistry Essentials: Units, Measurement, and Problem Solving

Classification of Matter

Concept: Classification of Matter

Matter is anything that occupies space and has mass. Chemistry studies matter and its changes, focusing on the atom as the basic functional unit.

• Pure Substances: Composed of only one type of atom or molecule.

• Mixtures: Composed of two or more different elements or compounds physically mixed together.

Type	Description
Element	Cannot be broken down into simpler substances.
Compound	Composed of two or more elements chemically bonded.
Homogeneous Mixture	Uniform composition throughout (solution).
Heterogeneous Mixture	Non-uniform composition.

Example: Granite is a heterogeneous mixture; saline solution is a homogeneous mixture.

Physical and Chemical Changes

Concept: Physical Changes

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

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

Concept: Chemical Changes

Chemical changes result in new substances with different compositions and properties.

• Examples: Rusting iron, burning wood, cooking an egg.

Reversible & Irreversible Changes

• Reversible: Can be undone (e.g., phase changes: melting, freezing).

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

Example: Dissolving sugar in water is reversible; burning wood is irreversible.

Chemical and Physical Properties

Concept: Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes.

• Examples: Reactivity with acids, flammability, oxidation.

Concept: Physical Properties

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

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

Intensive vs. Extensive Properties

Intensive Properties

Do not depend on the amount of substance present.

• Examples: Density, melting point, boiling point.

Extensive Properties

Depend on the amount of substance present.

• Examples: Mass, volume, length.

Temperature and Temperature Conversion

Concept: Temperature

Temperature measures the average kinetic energy of particles in a substance.

• Thermal Energy: Total kinetic and potential energy of all atoms in an object.

Temperature Conversion

Temperature can be measured in Celsius (°C), Kelvin (K), and Fahrenheit (°F).

• $K = ^ ext{o}C + 273.15$

• $^ ext{o}F = rac{9}{5}^ ext{o}C + 32$

Scientific Notation

Concept: Scientific Notation

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

• Format: $a imes 10^n$ where $1 ext{ ≤ } a ext{ < } 10$ and $n$ is an integer.

Example: $6.68 imes 10^{12}$

SI Units and Measurements

SI Base Units

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 & Volume

• Perimeter: $P = 2l + 2w$

• Area: $A = l imes w$

• Volume: $V = l imes w imes h$

Metric Prefixes

Concept: Metric Prefixes

Metric prefixes are modifiers that act as multiples of base units.

Prefix	Symbol	Multiplier
kilo	k	$10^3$
centi	c	$10^{-2}$
milli	m	$10^{-3}$
micro	μ	$10^{-6}$
nano	n	$10^{-9}$

Significant Figures

Concept: Significant Figures

Significant figures are the digits in a measurement that contribute to its precision.

• Rules: 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.

Significant Figures in Calculations

• Multiplication/Division: Result has the same number of significant figures as the value with the fewest significant figures.

• Addition/Subtraction: Result has the same number of decimal places as the value with the fewest decimal places.

Conversion Factors & Dimensional Analysis

Concept: Conversion Factors

Conversion factors are ratios that relate two different units.

• Example: $1 ext{ hr} = 60 ext{ min}$

Dimensional Analysis

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

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

Density

Concept: Density

Density is the amount of mass per unit volume.

• Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

Density of Geometric Objects

• For cubes: $V = a^3$

• For spheres: $V = \frac{4}{3}\pi r^3$

• For cylinders: $V = \pi r^2 h$

Density by Water Displacement

• Volume displaced = Final volume - Initial volume

Example: If a solid increases water level from 200 mL to 265 mL, volume = 65 mL.

Additional info: These notes cover all foundational concepts in Ch.0 - Essentials: Units, Measurement, and Problem Solving, including classification of matter, physical and chemical changes, properties, temperature, scientific notation, SI units, metric prefixes, significant figures, conversion factors, dimensional analysis, and density.