Introduction to General Chemistry: Matter, Measurement, and Properties

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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.

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	Salt water

Physical and Chemical Changes

Physical Changes

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

Examples: Melting, freezing, dissolving, breaking.

Chemical Changes

Chemical changes 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 (melting, freezing, boiling).

Irreversible Changes

Irreversible changes cannot be undone easily, 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.

Examples: Flammability, reactivity with acid.

Physical Properties

Physical properties can be observed without changing the substance's identity.

Examples: 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.

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

Prefixes, SI Units, and Notation

SI prefixes are used to indicate multiples or fractions of units.

Prefix	Symbol	Factor	Value
kilo	k	103	1,000
centi	c	10-2	0.01
milli	m	10-3	0.001
micro	μ	10-6	0.000001

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

Numbers are written as a coefficient times 10 raised to a power.
Example:

Significant Figures

Rules for Significant Figures

Nonzero numbers 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: 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 will float; those with greater density will sink.

Density in 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 .