Chemistry: The Particle Nature of Matter

Chemistry, the Particle Nature of Matter

• Chemistry is the branch of science that studies matter, its properties, composition, characteristics, structural changes, and the energy released during such changes.
• The five branches of chemistry are: organic chemistry, inorganic chemistry, analytical chemistry, physical chemistry, and biochemistry.
• Organic chemistry focuses on the study of carbon and its compounds, including the chemistry of life.
• Inorganic chemistry investigates compounds not covered by organic chemistry, specifically those that do not contain a carbon-hydrogen (C-H) bond.
• Analytical chemistry involves the study of matter and the development of tools to measure its properties.
• Physical chemistry uses physics principles to study chemistry, often applying thermodynamics and quantum mechanics.
• Biochemistry studies chemical processes within living organisms.

Matter

• Matter is anything that occupies space and has mass.
• "Materia" (Latin) means material or stuff.
• Energy is not matter.

Physical Properties of Matter

• A physical property is observable or measurable without changing the substance's identity.
• Examples include viscosity (resistance to flow), conductivity (ability to transmit heat or electricity), malleability (ability to be hammered into a sheet), melting point, boiling point and density (mass compared to volume), solubility (ability to dissolve in another substance).

Two Common Separation Points

• Filtration separates materials based on particle size.
• Distillation separates substances based on boiling points.

Measurable Properties

• Mass: the amount of matter. Used with a triple beam balance or scale.
• Weight: the pull of gravity on an object. Units are grams or kilograms.
• Volume: the amount of space an object occupies. Measured differently for regular solids (using dimensions), irregular solids, and liquids (using graduated cylinder).

Chemical Properties of Matter

• A chemical property describes a substance's ability to undergo a change and form a new substance with different properties.
• Examples include flammability (ability to burn in the presence of oxygen) and reactivity.

Chemical Properties Table

• A table showing physical and chemical properties of different substances.

The 5 Physical States of Matter

• Bose-Einstein condensate: Exists at extremely low temperatures, particles are locked together and move as a single unit.

• Solids: Particles are tightly packed, fixed positions, definite shape and volume. Particles vibrate but do not move.

• Liquids: Particles are closely packed but able to move around. Have a definite volume but no definite shape.

• Gases: Particles are widely spread with high kinetic energy. They move freely and have no definite shape or volume.

• Plasma: Exists at extremely high temperatures. Particles are broken apart and move with high energy.

Kinetic Molecular Theory

• All matter is composed of atoms and molecules in constant motion.
• The energy of this motion is dependent on temperature.

Classification of Matter by Composition

• Pure substances: Composition does not change, single type of atom or molecule.
• Mixtures: Two or more types of atoms or molecules combined in variable proportions which give different properties.
  • Elements: pure substances that cannot be broken down.
  • Compounds: pure substances which can be decomposed into simpler substances.
  • Homogenous Mixtures: uniform composition
  • Heterogenous Mixtures: uneven composition

Building Molecules/Compounds

• Molecules are formed when atoms bond together.

• Compounds are substances containing two or more different types of atoms.

• Compounds are molecules.

Phase Changes

• Phase changes involve a change in state (solid, liquid, or gas) and involve the absorption or release of energy.

Melting Point/Boiling Point

• Substances change state at specific temperatures (temperatures at which matter changes phase) Melting point: solid to liquid, Boiling point: liquid to gas. Melting point and boiling point are tabulated.

Changes of State

• Melting: solid to liquid
• Freezing: liquid to solid
• Vaporization: liquid to gas (e.g., evaporation, boiling)
• Condensation: gas to liquid
• Sublimation: solid to gas
• Deposition: gas to solid

History of Atomic Theory

• Leucippus and Democritus (450 BCE): Proposed the idea of atoms as indivisible units.
• John Dalton (1803): Developed atomic theory with postulates about atoms.
• Joseph John Thomson (1904): Discovered the electron and proposed the plum pudding model of the atom.
• Ernest Rutherford (1911): Discovered the atomic nucleus and proposed a nuclear model of the atom.
• Niels Bohr (1913): Developed a planetary model of the atom, with quantized energy levels.
• Erwin Schrödinger and Werner Heisenberg (1920s): Developed the quantum mechanical model of the atom, which describes electrons as wave-like functions.

Isotopes

• Atoms of the same element with a different number of neutrons thus different mass numbers.

Periodic Table

• Elements are organized in a table based on their properties.

• Chemical properties of elements are periodic functions of their atomic numbers.

• Elements with similar properties are grouped together.

• Trends within the periodic Table exist like atomic size, metallic character, reactivity; electronegativity; and ionization energy.

Quantum Numbers

• Set of numbers describing electron properties such as energy level, shape, orientation, and spin.
• Four quantum numbers are needed to specify an electron- Principal, azimuthal, magnetic and spin.

Orbitals

• Region within an atom where an electron is most likely to be found.
• Each orbital can hold at most two electrons with opposite spins.

Electronic Configuration

• Arrangement of electrons in an atom. Based on aufbau principle, Pauli exclusion principle, and Hund’s rule.

Radioactive Isotopes

• Different isotopes of an element and the uses of radioisotopes such as Calcium-47, Chromium 51,lodine -131, and Copper 67 in medicine.