Properties of Gases, Liquids, and Solids

Characteristic Properties of Gases, Liquids, and Solids

• Gases have large distances between molecules, leading to compressibility, expansion to fill containers, and low density.
• Liquids have molecules close together, resulting in limited compressibility, high density, and a defined volume. They can flow and take the shape of their container.
• Solids have rigid molecules with little freedom of motion, making them incompressible with defined shapes and volumes.
• Intermolecular forces, attractive forces between molecules, play a significant role in the condensed phases (liquids, solids).
• Intramolecular forces are the forces holding atoms together within a molecule (chemical bonding).

Types of Intermolecular Forces

• Van der Waals forces attract molecules in condensed phases.
  • Dipole-dipole forces occur between polar molecules due to uneven electron distribution, creating partial charges.
  • Ion-dipole forces exist between ions and polar molecules, as seen in hydration of ionic compounds with water.
  • Dispersion (London) forces are temporary dipoles induced in nonpolar molecules. These forces increase with molar mass, as heavier molecules have more electrons, leading to stronger dispersion forces.
• Hydrogen bonds are a specific type of dipole-dipole interaction, involving a hydrogen atom in a polar bond (N-H, O-H, or F-H) and an electronegative N, O, or F atom with lone pairs.

Properties of Liquids

• Surface tension measures the elastic force of a liquid's surface, reflecting the energy needed to stretch the surface. Liquids with strong intermolecular forces have higher surface tension.
  • Capillary action, water rising in a tube, results from cohesion (attraction between like molecules) and adhesion (attraction between unlike molecules).
• Viscosity measures a fluid's resistance to flow. Viscosity decreases with increasing temperature, and liquids with strong intermolecular forces have higher viscosity.

Categories of Solids

• Crystalline solids have a rigid, long-range order with atoms, molecules, or ions occupying specific positions.
• Amorphous solids lack a well-defined arrangement and long-range molecular order.

Crystal Structure

• A unit cell is the basic repeating structural unit of a crystalline solid, forming the crystal lattice when repeated in three dimensions.

Packing Spheres

• Coordination number represents the number of atoms surrounding a central atom in a crystal lattice, indicating packing density.
• Simple cubic cells have a coordination number of 6.

Semiconductors

• Semiconductors are materials that are normally nonconductors, but conduct electricity at higher temperatures or when combined with impurities.
• Silicon and germanium are key semiconductors.
• Doping involves introducing impurities to enhance conductivity.
  • Donor impurities (like phosphorus in silicon) provide extra electrons (n-type semiconductors).
  • Acceptor impurities (like boron in silicon) create electron vacancies (p-type semiconductors).

Superconductors

• Superconductivity is a state where a metal conducts electricity with no energy loss or resistive heating, achieved by minimizing atomic vibrations through cooling.

Polymers

• Polymers are large molecules composed of covalently linked chains of smaller repeating units called monomers.
• Natural Polymers include proteins, nucleic acids, cellulose (polysaccharides), and rubber (polyisoprene).
• Synthetic polymers are organic compounds, such as nylon, Dacron, and Lucite.

Synthetic Organic Polymers

• Synthetic polymers are created by joining monomers together through addition or condensation reactions.
• Addition reactions involve unsaturated compounds with double or triple bonds, like C=C and C≡C.
  • Polyethylene is a homopolymer (made from one monomer type), used in films and packaging.
  • Teflon (polytetrafluoroethylene) and poly(vinyl chloride) (PVC) are also examples of homopolymers.
• Condensation reactions involve two functional groups on monomers reacting to form small molecules, which are then split off, joining the remaining parts of the monomers.
  • Nylon (polyamide) and Dacron (polyester) are examples of condensation polymers used in fiber manufacturing.

Explore the key characteristics of gases, liquids, and solids in this quiz. Understand the differences in molecular distances, compressibility, density, and intermolecular forces that define each state of matter. Test your knowledge on intermolecular forces and their effects on physical properties.