Introduction to General Chemistry: Matter, Measurement, and Properties

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Introduction to General Chemistry

Matter and Its Classification

Chemistry is the scientific study of matter, its properties, composition, and the changes it undergoes. Matter is anything that occupies space and has mass. It can be classified based on its physical state and composition.

Physical States of Matter: Solid, liquid, and gas.
Classification by Composition: Elements, compounds, and mixtures.

Type	Definition	Example
Element	Pure substance made of a single type of atom	Oxygen (O2)
Compound	Pure substance made of two or more elements chemically combined	Water (H2O)
Mixture	Physical combination of two or more substances	Air, saltwater

Physical and Chemical Changes

Physical Changes

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

Examples: Melting ice, tearing paper, dissolving sugar in water.

Chemical Changes

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

Examples: Burning wood, rusting iron, baking a cake.

Phase Changes: Reversible and Irreversible

Reversible Changes

Reversible changes can be undone, such as phase changes between solid, liquid, and gas (melting, freezing, boiling).

Irreversible Changes

Irreversible changes cannot be easily undone, such as burning or cooking.

Phase Change	Reversible	Irreversible
Melting	Yes	No
Burning	No	Yes

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes, such as flammability or reactivity.

Physical Properties

Physical properties can be observed or measured without changing the substance's identity, such as color, melting point, and density.

Intensive vs. Extensive Properties

Intensive Properties: Do not depend on the amount of substance (e.g., density, boiling point).
Extensive Properties: Depend on the amount of substance (e.g., mass, volume).

Property Type	Examples
Intensive	Density, melting point
Extensive	Mass, volume, length

SI Units and Measurements

SI Base Units

The International System of Units (SI) is used 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

Metric Prefixes

Metric prefixes indicate multiples or fractions of units.

Prefix	Symbol	Multiplier
kilo	k	103
centi	c	10-2
milli	m	10-3
micro	μ	10-6
nano	n	10-9

Temperature and Scientific Notation

Temperature Scales

Temperature can be measured in Celsius, Kelvin, or Fahrenheit.

Scale	Conversion Formula
Celsius to Kelvin
Celsius to Fahrenheit

Scientific Notation

Scientific notation expresses numbers as a product of a coefficient and a power of ten, e.g., .

Significant Figures

Rules for Significant Figures

Nonzero digits are always significant.
Any zeros between significant digits are significant.
Leading zeros are not significant.
Trailing zeros are significant only if there is a decimal point.

Significant Figures in Calculations

For multiplication/division: The result has the same number of significant figures as the measurement with the fewest significant figures.
For 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 the same quantity in different units.

Quantity	Conversion	Factor
Length	1 km = 1000 m	1 km / 1000 m
Mass	1 kg = 1000 g	1 kg / 1000 g

Dimensional Analysis

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

Density and Measurement

Density

Density is the mass per unit volume of a substance.

Formula:

Density of Common Objects

Objects with density greater than water sink; those with less density float.

Density by Water Displacement

Density can be measured by dividing the mass of an object by the volume of water it displaces.

Example: If a metal block has a mass of 50 g and displaces 20 mL of water, its density is .

Additional info: These foundational concepts are essential for understanding more advanced topics in general chemistry, such as stoichiometry, thermodynamics, and chemical equilibrium.