States of Matter and Physical Properties

States of Matter

• Matter exists in three primary states: solid, liquid, and gas.
• State changes are influenced by temperature.
• Melting: solid to liquid
• Evaporation: liquid to gas
• Condensation: gas to liquid
• Freezing: liquid to solid
• Sublimation: solid to gas
• Deposition: gas to solid

Physical Properties of Solids

• Solids exhibit physical properties like color and shininess.
• These properties may or may not change during state transitions.
• Melting point: temperature at which a solid becomes a liquid.
• Boiling point: temperature at which a liquid transforms into a gas.
• Hardness: resistance of a substance to being scratched.
• Malleability: ability of a substance to be shaped.
• Ductility: ability of a substance to be drawn into wires.
• Crystal shape: characteristic geometric structure of a crystalline solid.
• Solubility: capacity for a substance to dissolve into another.
• Density: measure of how closely packed particles are in a substance.
• Conductivity: ability to conduct heat or electricity.

Rules Governing Matter

• Matter comprises particles.
• Particles are spaced apart.
• Particles attract one another.
• Particles are constantly moving.
• Increased energy leads to faster particle movement and greater separation.
• Phase: another term for state of matter (solid, liquid, gas).

Mixtures and Pure Substances

• Mixtures contain two or more different kinds of particles.
• Pure substances consist of only one type of particle.
• Mixtures can be homogeneous (uniform particle distribution) or heterogeneous (non-uniform particle distribution).
• Homogeneous mixtures (solutions) cannot distinctly identify the different components; heterogeneous mixtures (mechanical mixtures) clearly display different components.

Physical and Chemical Changes

• Physical changes alter the form of a substance without changing its chemical composition.
• No new substances are formed during a physical change, and the change can often be reversed.
• State changes are physical changes.
• Chemical changes alter the chemical composition of a substance.
• Chemical changes form new substances, and these changes are typically irreversible..
• Chemical changes are always accompanied by physical changes.

Identifying Chemical Changes

• Several indicators signal chemical changes:
  • Heat production or absorption
  • pH change
  • Consumption of reactants
  • Color change
  • Gas bubble formation
  • Precipitate (solid) formation in a liquid

Classifying Substances

• Substances can be classified according to their observable (physical) and reactive (chemical) properties.
• Any measurable quality observed without altering chemical composition is a physical property.
• Chemical properties describe how a substance interacts with another.

Laws and Theories

• Laws summarize observations (e.g., gravity).
• Theories explain why observations happen (e.g., gravity's cause)

The Law of Conservation of Mass

• During chemical reactions, the total mass of the new substances remains the same as the original substances. Meaning: Mass cannot be created or destroyed.

Atomic Structure

• Atoms are the fundamental building blocks of substances.
• Atoms are composed of subatomic particles: protons, neutrons, and electrons.
• Protons (+) reside in the nucleus.
• Neutrons (neutral charge) are found in the nucleus.
• Electrons (-) orbit the nucleus.

Atomic Models

• Thomson's Plum Pudding Model: electrons scattered within a positively charged "pudding."
• Rutherford's Planetary Model: the nucleus holds positive charge, with orbiting electrons.
• Bohr's Model: electrons occupy fixed energy levels (shells).
• Electron Cloud Model: electrons' positions are probabilistic, described by wave functions.

Elements

• Elements are pure substances composed of the same type of atoms.
• Atomic symbol: abbreviation.
• Atomic number: number of protons.
• Atomic mass: average mass of naturally occurring isotopes.
• Number of neutrons = atomic mass - atomic number

Ions

• Ions are atoms that have gained or lost electrons, becoming electrically charged.
• Anions (negatively charged) result from electron gain.
• Cations (positively charged) result from electron loss.