Chemistry Solutions and Mixtures

Solutions and Mixtures

• Solutions are homogenous mixtures of one or more solutes dissolved in a solvent.
• Examples include sodas, seawater, air, and metal alloys.
• Solutions cannot visually differentiate their individual components.
• An ionic solute dissolved in a solvent dissociates into cations and anions.
• Solutions can be classified by the state of matter of solute and solvent:
  • Solid-solid (e.g., bronze)
  • Liquid-liquid (e.g., hand sanitizer)
  • Gas-gas (e.g., air)
  • Solid-liquid (e.g., sports drinks)
  • Liquid-gas (e.g., sodas)
  • Gas-solid (e.g., hydrogen gas and platinum)
• Heterogeneous mixtures have uneven distribution of constituent particles (e.g., sand and water).
• Suspensions are heterogeneous, separate into layers (e.g., sand in water).
• Colloids are heterogeneous, do not separate (e.g., milk).
• Mixtures have variable proportions of elements, making them impure substances.

Pure Substances

• Pure substances are made of one type of element or compound, for instance, table salt or water.
• Purity is measured, ideally 100%, but rarely achieved.
• Refining methods, like distillation, are used to improve purity.
• Pure substances have specific melting & boiling points.
• Conductivity can vary based on purity.
• Pure substances are predictable in chemical reactions.

Separation of Mixtures

• Mixtures are formed when two or more components are physically combined.
• Solutions and alloys are homogeneous mixtures (e.g., air, steel, saltwater, gasoline).
• Suspensions and colloids are heterogeneous mixtures (e.g., pizza, a bag of marbles, sandy water).
• Various physical methods separate mixture components (chromatography, distillation, evaporation, crystallization, filtration, magnetism, manual separation).
• Chromatography separates components based on different affinities for mobile and stationary phases.
• Retention factor (Rf) calculation: (distance traveled by component/distance traveled by solvent).
• Distillation separates mixtures based on differing boiling points.
• Evaporation/Crystallization separates mixtures based on vaporization.
• Filtration separates solids from liquids in heterogeneous mixtures.
• Dissolving, then separating, is useful for multiple component mixtures.
• Magnetism separates magnetic metals.

Atoms and Subatomic Particles

• Atoms consist of protons, neutrons, and electrons.
• Protons are positively charged, located in the nucleus, with a mass of 1 amu.
• Neutrons have no charge, located in the nucleus, with a mass of 1 amu.
• Electrons are negatively charged, outside the nucleus, with negligible mass.
• Atomic number (Z) is the number of protons in an atom's nucleus, unique to each element.
• Mass number (A) is the sum of protons and neutrons.
• Isotopes are atoms of the same element with different numbers of neutrons.
• Atomic mass is the weighted average of isotopes' mass numbers.

The Periodic Table

• The periodic table organizes elements based on atomic number (number of protons).
• Historical developments include Dobereiner's Law of Triads, Newlands' Law of Octaves, and Mendeleev's periodic table.
• Moseley arranged the modern periodic table based on proton number.
• Periods are horizontal rows, groups are vertical columns.
• Elements are classified as metals, nonmetals, or metalloids.
• Periodic trends predict element properties (e.g., valence electrons, atomic radius, ionization energy).

Metals

• Metals are shiny, hard, ductile, malleable, and good conductors.
• Five main metal groups: alkali, alkaline earth, transition, lanthanides, actinides.
• Alkali and alkaline earth metals are in the s-block.
• Transition metals are in the d-block.
• Lanthanides and actinides are in the f-block.
• Examples include iron, gold, silver, zinc.
• Low ionization energy leads to high reactivity.
• Metals form hydroxides, halides, and oxides.
• Transition, lanthanide, and actinide metals form complexes.

Metalloids

• Metalloids have properties of both metals and nonmetals.
• Examples include boron, silicon, germanium, arsenic, antimony, tellurium (and sometimes bismuth, polonium, astatine).
• They are typically solids, have a metallic luster, are brittle, and are semiconductors.
• Properties (melting/boiling point, reactivity) vary.
• Their behavior depends on valence electrons and involved elements in reactions.

Nonmetals

• Nonmetals typically have high ionization energies and electronegativities.
• They are poor conductors of heat and electricity.
• Nonmetals are reluctant to give up electrons.
• Majority of nonmetals are gases at room temperature; some are solids, one is a liquid
• Nonmetals form covalent bonds when reacting with each other.
• Located on the right side of the periodic table (except hydrogen).
• Common nonmetal families: halogens, noble gases, some metalloids.