Introduction to Matter & Measurement: General Chemistry Study Notes

Introduction to General Chemistry

Classification of Matter

Matter is anything that occupies space and has mass. In chemistry, matter is classified based on its composition and properties.

• Pure Substances: Matter with a fixed composition. Includes elements and compounds.

• Mixtures: Matter composed of two or more substances physically combined. Can be homogeneous (uniform composition) or heterogeneous (non-uniform composition).

Classification Table:

Type	Definition	Examples
Element	Pure substance of one kind of atom	Oxygen (O2), Gold (Au)
Compound	Pure substance of two or more elements chemically bonded	Water (H2O), Sodium chloride (NaCl)
Homogeneous Mixture	Uniform composition throughout	Salt water, Air
Heterogeneous Mixture	Non-uniform composition	Salad, Sand and iron filings

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

Physical and Chemical Changes

Physical Changes

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

• Examples: Melting, boiling, dissolving sugar in water

Chemical Changes

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

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

Reversible and Irreversible Changes

Phase Changes

Phase changes (e.g., melting, freezing, vaporization) are typically reversible physical changes.

Bond Forming	Bond Breaking
Gas → Liquid → Solid	Solid → Liquid → Gas

Irreversible Changes

Irreversible changes cannot be undone by simple physical means (e.g., burning paper).

Chemical and Physical Properties

Chemical Properties

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

• Examples: Reactivity with acids, flammability, oxidation

Physical Properties

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

• 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 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
Electric current	ampere	A
Luminous intensity	candela	cd

Perimeter, Area, and Volume

• Area: $A = l \times w$

• Volume (rectangular): $V = l \times w \times h$

Metric Prefixes

Metric Prefix Multipliers

Metric prefixes indicate multiples or fractions of base units.

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

Example: To convert 654 kg to g, multiply by $10^3$.

Temperature

Thermal Energy and 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

• Celsius to Kelvin: $K = ^\circ C + 273.15$

• Celsius to Fahrenheit: $^\circ F = \frac{9}{5}(^\circ C) + 32$

Scientific Notation

Format for Scientific Notation

Scientific notation expresses numbers as a coefficient times a power of ten.

• General form: $a \times 10^n$

• Example: $6.68 \times 10^{-12}$

Converting Between Standard and Scientific Notation

• Move the decimal point to create a coefficient between 1 and 10.

• Count the number of places moved to determine the exponent.

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 are significant only if there is a decimal point.

Significant Figures in Calculations

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

• Addition/Subtraction: The result has 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: $1 \text{ hour} = 60 \text{ minutes}$

Dimensional Analysis

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

• Set up the problem so that units cancel appropriately.

• Multiply by conversion factors until the desired unit is obtained.

Density

Density Formula

Density is the amount of mass per unit volume.

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

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

Density of Geometric Objects

• Calculate volume using geometric formulas, then apply the density formula.

• Example: For a cube, $V = a^3$

Density by Water Displacement

• For irregular objects, volume can be measured by water displacement.

• Subtract initial water volume from final volume after submerging the object.

Additional info: These notes cover foundational concepts in general chemistry, including matter classification, properties, measurement, and basic calculations, suitable for introductory college-level study.