Introduction to General Chemistry: Matter, Properties, and Measurement

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Introduction to General Chemistry

Matter and Its Classification

Chemistry is the study of matter, its properties, 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 State: Solid, liquid, or gas.
Composition: Elements, compounds, or mixtures.

Type	Definition/Example	Symbol
Element	Pure substance made of a single type of atom	H, O, Na
Compound	Pure substance made of two or more elements chemically combined	H2O, CO2
Mixture	Physical combination of two or more substances	Air, saltwater

Physical and Chemical Changes

Physical Changes

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

Examples: Melting, freezing, dissolving, breaking

Chemical Changes

Chemical changes (chemical reactions) result in the formation of new substances with different properties.

Examples: Burning, rusting, digestion

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 undone by simple physical means (e.g., burning paper).

Phase Change	Solid → Liquid	Liquid → Gas	Solid → Gas
Name	Melting	Boiling	Sublimation

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes (e.g., flammability, reactivity).

Physical Properties

Physical properties can be observed without changing the substance's identity (e.g., color, melting point, 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

Derived Units, Area, and Volume

Area:
Volume:

Metric Prefixes

Metric Prefix Multipliers

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

Temperature and Scientific Notation

Temperature Scales

Scale	Conversion Formula
Celsius to Kelvin
Celsius to Fahrenheit

Scientific Notation

Expresses numbers as a coefficient times a power of ten (e.g., ).

Significant Figures

Rules for Significant Figures

Nonzero numbers are always 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

Addition/Subtraction: Result has the same number of decimal places as the measurement with the fewest decimal places.
Multiplication/Division: Result has the same number of significant figures as the measurement with the fewest significant figures.

Conversion Factors and Dimensional Analysis

Conversion Factors

Conversion factors are ratios used to express the same quantity in different units.

Quantity	Equivalent	Factor
Length	1 km = 1000 m	1000
Mass	1 kg = 1000 g	1000

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

Density and Measurement

Density

Density is the ratio of mass to volume.

Formula:

Density of Common Objects

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

Density in Water Displacement

Density can be measured by water displacement: Submerge an object in water and measure the volume of water displaced to find the object's volume.

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