Properties of Liquids and Intermolecular Forces

Properties of Liquids and Intermolecular Forces

• Fluid: A substance that can flow (gas or liquid).
• Surface Tension: The elastic force in a liquid's surface, the energy needed to increase/stretch the surface area of a liquid by a unit area. Similar to an elastic film.
• Viscosity: A measure of a liquid's resistance to flow. Higher viscosity = slower flow. Measured in centipoise. Water (20°C) = 1 centipoise (0.001 Pa/s). Viscosity increases with stronger intermolecular forces and larger molecule size.
• Capillary Action: The tendency of a liquid to rise or be drawn into narrow tubes or openings. Driven by intermolecular attraction (cohesion and adhesion) between the liquid and the solid material. Cohesion = attraction between liquid molecules, adhesion = between unlike molecules.
• Meniscus: The curved surface of a liquid in a container. Concave meniscus forms when adhesion is stronger than cohesion, convex meniscus forms when cohesion is stronger than adhesion.

Vapor Pressure and Equilibrium

• Vapor: Gaseous substance that exists as a liquid or solid at normal temperatures.
• Vapor Pressure: The rate of condensation of gas equals the rate of evaporation of liquid = equilibrium. The maximum vapor pressure of a liquid at a given temperature. It increases with temperature.

Properties of Solids and Intermolecular Forces

• Crystalline Solid: A solid with components (atoms, molecules, or ions) arranged in a highly ordered microscopic structure.
• Amorphous Solid: A solid with randomly oriented components. Considered supercooled liquids, examples include glass, plastic, coal, and rubber.
• Ionic Crystal: A solid made up of positively and negatively charged ions held together by electrostatic forces.
• Network Solid (Covalent Network Crystal): A solid in which atoms are bonded by covalent bonds in a continuous network extending throughout the material.
• Molecular Crystal: A solid made up of molecules held together by van der Waals forces.
• Unit Cell: The smallest subunit of a crystal lattice that can be repeated over and over to create the entire crystal.
• Ion: An atom or group of atoms with a net positive or negative charge.
• Electrostatic Bonding: The attraction between oppositely charged ions in a chemical compound.

Types of Solids

• Crystalline Solids: Fixed, repeating, geometric patterns (lattices). Example: NaCl, CuSO4, sugar.

• Crystalline solids exhibit a high level of order, in terms of crystal lattices, which are the basic repeating units within their structure. At a molecular level, all crystals exhibit a repeating pattern for how atoms, molecules, or ions are organized within the solid.

• Amorphous solids lack the highly ordered structure of crystalline solids. These solids have disordered arrangements of atoms, ions, or molecules, which may be supercooled liquids or a liquid at that particular temperature.

• Amorphous Solids: Random orientations of components. Example: glass, plastic, rubber.

• Metallic Crystals: Electrostatic interactions between cations and delocalized electrons (sea of electrons). Examples include Iron, Silver, Gold.

• Ionic Crystals: Strong electrostatic interactions between cations and anions. Examples include NaCl, Ca(NO3)2.

• Molecular Crystals: Molecules held together by van der Waals forces. Examples include noble gases, methane, sucrose, and dry ice.

• Covalent Network Crystals: Atoms held together by covalent bonds in a continuous network. Examples include diamond (C) and quartz (SiO2).

This quiz explores key concepts related to the properties of liquids and the intermolecular forces that influence them. Test your understanding of terms like surface tension, viscosity, and capillary action, as well as how these properties affect liquid behavior in various scenarios.