Introduction to Matter & Measurement: General Chemistry Study Notes

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 two main types:

• Pure Substances: Composed of only one kind of atom or molecule. Examples include elements (e.g., gold, oxygen) and compounds (e.g., water, sodium chloride).

• Mixtures: Composed of two or more substances physically mixed together. 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.

Classification Table

Type	Definition	Example
Element	Pure substance of one kind of atom	Gold (Au)
Compound	Pure substance of two or more elements chemically bonded	Water (H2O)
Homogeneous Mixture	Uniform composition	Salt water
Heterogeneous Mixture	Non-uniform composition	Salsa

Physical and Chemical Changes

Physical Changes

Physical changes alter the physical state of a substance without changing its composition. Examples include melting, boiling, and dissolving sugar in water.

• Physical Change: No new substance is formed.

Chemical Changes

Chemical changes result in the formation of new substances with new chemical bonds and properties. Examples include burning wood and cooking an egg.

• Chemical Change: New substances are formed.

Reversible and Irreversible Changes

Phase Changes

Phase changes, such as melting, freezing, and boiling, are typically reversible. Chemical reactions, such as combustion, are usually irreversible.

• Reversible Change: Can be undone (e.g., melting ice).

• Irreversible Change: 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 include flammability and reactivity with acids.

Physical Properties

Physical properties can be observed without changing the chemical identity of a substance. Examples include color, melting point, and density.

Intensive vs. Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present. Examples include density, boiling point, and color.

Extensive Properties

Extensive properties depend on the amount of substance present. Examples include mass, volume, and length.

SI Units and Measurements

SI Base Units

The International System of Units (SI) is based on seven 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, and Volume

• Perimeter: $P = 2l + 2w$

• Area: $A = l imes w$

• Volume: $V = l imes w imes h$

Metric Prefixes

Metric Prefix Multipliers

Metric prefixes are modifiers that multiply SI units by powers of ten. Examples include kilo- ($10^3$), centi- ($10^{-2}$), and milli- ($10^{-3}$).

Temperature and Scientific Notation

Temperature

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

• Temperature: Average kinetic energy of an object.

Temperature Conversion Formulas

• $T_{K} = T_{C} + 273.15$

• $T_{F} = rac{9}{5}T_{C} + 32$

Scientific Notation

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

• Used to express very large or small numbers.

Significant Figures

Rules for Significant Figures

• 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: Result has the same number of sig figs as the value with the fewest sig figs.

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

Conversion Factors and Dimensional Analysis

Conversion Factors

Conversion factors are ratios that relate two different units. They are used to convert measurements from one unit to another.

Common Conversion Factors Table

Conversion	Factor
1 inch	2.54 cm
1 year	365 days
1 kg	1000 g

Dimensional Analysis

Dimensional analysis is a method for converting between units using conversion factors. The general format is:

• Given amount × Conversion factor = End amount

Density

Density Formula

• Density: $D = rac{m}{V}$, where $m$ is mass and $V$ is volume.

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

Density of Geometric Objects

• For cubes: $V = a^3$

• For spheres: $V = rac{4}{3}\pi r^3$

• For cylinders: $V = \\pi r^2 h$

Density by Water Displacement

Water displacement is used to measure the volume of irregularly shaped objects. The volume displaced equals the volume of the object.

Summary Table: Key Concepts

Concept	Definition	Formula/Example
Classification of Matter	Pure substances vs. mixtures	Element, compound, homogeneous, heterogeneous
Physical/Chemical Change	Change in state vs. change in composition	Melting vs. burning
Properties	Chemical vs. physical, intensive vs. extensive	Density, mass, reactivity
SI Units	Standard units for measurement	kg, m, s, K, mol, A, cd
Scientific Notation	Expressing large/small numbers	$a imes 10^n$
Significant Figures	Precision in measurement	Rules for counting sig figs
Conversion Factors	Unit conversion	1 in = 2.54 cm
Density	Mass per unit volume	$D = rac{m}{V}$

Additional info: These notes cover foundational concepts from Chapter 1 of a General Chemistry textbook, including matter, measurement, and basic mathematical operations relevant to laboratory work.