Chapter 1 Essential Ideas: 1.2 Phases and Classification of Matter

Phases and Classification of Matter

Core topics: Atoms and Molecules; Classifications; Mass and Weight; Conservation of Matter

Atom: the smallest particle of an element; cannot be split via chemical means.
Molecule: made up of individual atoms; can be the same or different elements.
Element: cannot be decomposed into simpler substances by chemical means.
Compound: combination of elements; held together by chemical bonds; can be broken down into elements by chemical processes.
Ethanol: ext{CH}3 ext{CH}2 ext{OH}

Compounds: combination of elements held together by chemical bonds; can be broken down into elements by chemical processes.
Elements: cannot be decomposed into simpler substances by chemical means.

Homogeneous mixture: Uniform composition; appears uniform throughout (e.g., air, tea); you cannot see the individual parts.
Heterogeneous mixture: Variable composition; not uniform; components may be separated (e.g., oil and water).

Mass: Measure of the amount of matter; is a constant.
Weight: Measure of the gravitational force on a mass; varies with location (earth vs. moon).
Relationship to chemistry: Mass is invariant during chemical changes; mass conservation is fundamental to chemical reactions.
Law of Conservation of Mass (Matter): m{ ext{before}} = m{ ext{after}} during chemical processes.
Note on gravity: Weight can change with gravitational field; mass remains the same regardless of location.

Mass is a scalar quantity representing the amount of matter in an object.
Weight is a force given by W = m g, where g is the local gravitational acceleration.

Fundamental principle: During any physical or chemical change, the total amount of matter remains constant (though it may change form).
Practical implication: In reactions, you must account for all products and reactants to observe mass balance.

Ethanol structure as an example of a compound: ext{CH}3 ext{CH}2 ext{OH} represents a molecule composed of atoms bonded together.
Ethanol illustrates how compounds are built from elements and can be broken down into elements by chemical processes.

Homogeneous mixture: uniform composition throughout; examples include air and tea.
Heterogeneous mixture: non-uniform composition; components are distinguishable; example is oil in water.

Understanding matter types and phases helps predict physical behavior, separation techniques, and reaction outcomes in laboratory and industry.
Classification into elements, compounds, and mixtures guides how substances can be separated, combined, or transformed.
The conservation principles underpin quantitative chemical analysis, reaction stoichiometry, and mass balance in processes.

Mass: m = ext{amount of matter}; constant under chemical change.
Weight: W = m g; depends on gravitational acceleration g.
Conservation of Mass: m{ ext{before}} = m{ ext{after}} in chemical reactions.
Ethanol formula: ext{CH}3 ext{CH}2 ext{OH}.
Phases: Solid (definite shape and volume); Liquid (definite volume); Gas (no definite shape or volume).
Homogeneous: uniform throughout; Heterogeneous: non-uniform; separation possible.