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.

Matter: Anything that has mass and occupies space.
Classification by State: Solid, liquid, gas.
Classification by Composition: Element, compound, mixture.

State	Arrangement of Particles	Shape/Volume	Example
Solid	Particles close together in fixed, rigid structure	Definite shape and volume	Ice
Liquid	Particles close but can move past each other	Definite volume, no definite shape	Water
Gas	Particles far apart, move freely	No definite shape or volume	Oxygen (O2)

Physical and Chemical Changes

Physical Changes

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

Examples: Melting, freezing, boiling, dissolving

Chemical Changes

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

Examples: Rusting of iron, burning of wood

Phase Changes: Reversible and Irreversible

Reversible Changes

Reversible changes can be undone, such as melting and freezing.

Irreversible Changes

Irreversible changes cannot be undone by simple physical means, such as burning or digestion.

Phase Change	Reversible	Irreversible
Melting/Freezing	Yes	No
Burning	No	Yes

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes, forming new substances.

Example: Flammability, reactivity with acid

Physical Properties

Physical properties can be observed or measured without changing the substance's composition.

Example: Color, melting point, density

Intensive vs. Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present.

Examples: Density, boiling point, color

Extensive Properties

Extensive properties depend on the amount of substance present.

Examples: Mass, volume, length

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. Each physical quantity has a standard unit.

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. The Kelvin scale is the SI unit for temperature.

Scale	Conversion Formula
Celsius to Kelvin

Scientific Notation

Scientific notation expresses numbers as a multiple of a power of ten, making it easier to handle very large or small values.

General form:

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

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

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.

Example: To convert 5 km to meters:

Density and Measurement

Density

Density is the mass per unit volume of a substance.

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, especially for irregular solids. The volume of water displaced equals the volume of the object.

Example: If a solid displaces 10 mL of water and has a mass of 25 g, its density is