Chapter 11 – Liquid and Intermolecular Forces

States of Matter Solid- matter that can not flow (definite shape) and has definite volume Liquid- definite volume but takes the shape of its container and can flow Gas- a substance without definite volume or shape and can flow

States of Matter Solid Liquid Gas Definite Volume? Definite Shape? Will it Compress? Solid Liquid Gas

Intramolecular & Intermolecular Forces Intramolecular forces hold atoms together in a molecule. Intermolecular forces are attractive forces between molecules Ex: 41 kJ vaporizes 1 mole of water (Inter) Ex: 930 kJ to break all O-H bonds in 1 mole of water (Intra) Intermolecular forces are weaker than intramolecular forces Many physical properties can be measured by intermolecular forces like boiling points, melting points, viscosity, surface tension, and capillary rise.

Types of Intermolecular Force Dispersion Forces (or London dispersion forces): Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules. Ex: All molecules Dipole–Dipole forces: Attractive forces between polar molecules. Ion–Dipole forces: Attractive forces between an ion and polar molecule

Practice Questions Ex: What type(s) of intermolecular forces exist between each of the following molecules? CH4 SO2 CH3Cl NaCl (aq) CS2

Hydrogen Bonding Hydrogen bonding is a special dipole–dipole interactions between the H atom when it is bonded to N, O, or F. Hydrogen bonding arises in part from the high electronegativity of nitrogen, oxygen, and fluorine.

Properties of Liquids Cohesion is the intermolecular attraction between like molecules. Ex: Mercury has stronger cohesive forces with itself (upper meniscus). Adhesion is an attraction between unlike molecules (lower meniscus). Ex: Water has stronger adhesive forces with glass Viscosity is a measure of the fluid’s resistance to flow. Molecules with strong intermolecular forces have a high viscosity.

Properties of Liquids Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit area. Molecules with strong intermolecular forces have high surface tension

Phase Change of Water Liquid Gas Solid melting vaporization freezing condensation

Heating Curve for H2O Gas Temperature → Liquid Solid Heat Supplied → Vaporization Condensation Temperature → Melting Freezing Heat Supplied →

Vapor Pressure The boiling point of a liquid is the temperature at which its vapor pressure equals atmospheric pressure. The normal boiling point is the temperature at which its vapor pressure is atmospheric pressure (1 atm).

Phase Diagram of Water A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas. The melting, boiling, and sublimation points are at different pressures.

Phase Diagram of Carbon Dioxide CO2 cannot exist in the liquid state at pressures below 5.11 atm (triple point) CO2 sublimes at normal pressures.