Week 2-3 - Chapter 2.pdf

C H E M I S T R Y 1 0 1 GENERAL 2 CHEMISTRY CLASS Week 2 Intermolecular Forces of Liquids and Solids 1. Types and properties of solids 2. Crystalline and amorphous solids 3. Types of Crystals...

C H E M I S T R Y 1 0 1 GENERAL 2 CHEMISTRY CLASS Week 2 Intermolecular Forces of Liquids and Solids 1. Types and properties of solids 2. Crystalline and amorphous solids 3. Types of Crystals a. Ionic b. covalent, c. molecular, and d. metallic 4. Phase Changes Objectives At the end of the lesson students are able to; 1. explain the kinetic molecular model of solids, 2. differentiate the Properties of solids, 3. analyse the intermolecular forces of attraction exist between particles of solids, and 4. appreciate the chemistry of things around us. LESSON 3: Types and Properties of Solids Solids “Solid as a rock, “ is the description of solid – something that is hard, unyielding, with a definite shape and volume. Many things other than rocks are solids. In fact, solids are more common than liquids. This diagram shows the particles of a gas, liquid and solid. Kinetic-Theory Description of the Solid State According to the kinetic theory, the motion of solid particles can be described as…. Lower kinetic energy, less motion, more packed particles, and higher intermolecular forces (IMF) Intermolecular forces between particles are therefore much more effective in solids. These hold particles of a solid in relatively fixed positions, with only vibrational movement. Solids are more ordered than liquids and gases. Properties of Solids and the Particle Model – Definite shape and volume - solids maintain a definite shape without a container. Volume is constant due to closely packed particles. Non-fluid- particles can’t flow because particles are held in relatively fixed positions. Definite melting point - The temperature at which the kinetic energy of the particles are able to overcome the attractive forces holding them together in fixed positions (crystalline only) High Density- solids are packed more closely than that of a liquid or gas. Incompressible - particles are packed so close together there is virtually no space between them Slow Diffusion – much slower than liquids due to the high IMF’s between particles. Structure of Solids Two ways to categorize solids Crystalline Amorphous (non-crystalline) Crystalline Solid Atoms, Ions, or molecules are ordered in well-defined arrangements. Rigid and long range order of its atoms. Solids have flat surfaces or faces Sharp angles Have regular shape EX: Quartz, diamond, sodium Chloride.  Classification of Crystalline Solids Components that Type of interaction Type occupy the lattice between Components Typical properties Examples points of Lattice Ionic Ions Ionic Hard; high melting NaCl, CaF2 point; insulating as a solid but conducting when dissolved Molecular Discrete molecules Dipole-dipole and/or Soft; low melting Ice, dry ice (solid CO2) London dispersion point forces Metallic Metal atoms Metallic Bonds Wide range of Silver, iron, brass hardness and melting points Network Nonmetal atoms Directional covalent Hard; high melting Diamond (leading to a giant point molecules) Group 8A Group 8A (Noble London dispersion Very low melting Argon gases) atoms forces points The Crystal Lattice and the Unit Cell The shape of a crystal depends on the arrangement of the particles within it. The smallest portion of the crystal which shows the complete pattern of its particles is called a unit cell. When unit cells are repeated in all directions, a crystal lattice is formed. The Crystal Lattice and the Unit Cell The smallest part of a crystal that will reproduce the crystal when repeated in a three dimensions. Three types Simple /primitive cubic cell Face centered cubic cell Body Centered There are 14 different unit-cell geometries that occur in crystalline solids. All unit cells are parallelepipeds (six-sided figures whose faces are parallelograms) and differ only in the lengths of the cell edges and angles between the edges. Seven basic types of unit cells TOPAZ GALENA ZIRCON Orthorhombic GYPSUM Cubic Tetragonal Monoclinic CALCITE TOURMALINE Rhombohedral Hexagonal AMAZONITE Triclinic Amorphous Solid (from the greek word “without form”) Lack a well defined arrangement No long range order IMF vary in strength Have poor-defined shapes EX: rubber, glass “Amorphous,” comes from the Greek for “without a shape.” Unlike crystals, amorphous solids do not have a regular, natural shape, but instead take on whatever shape imposed on them. Particle arrangement is not uniform; they are arranged randomly, like particles of a liquid. Examples of amorphous solids – glass, plastic, and synthetic fibers Amorphous solids are prepared by rapid cooling of thin film materials. Molecular examples Crystalline vs. Amorphous LESSON 4: Phase Changes and Phase Diagrams Changes of State Possible Changes of State Change of State Name Example Solid -> Liquid melting ice -> water Liquid -> Solid freezing water to ice Liquid -> Gas vaporization Br(l) -> Br(g) Gas -> Liquid condensation water vapor -> water Solid -> Gas sublimation dry ice -> CO2 gas Gas -> solid deposition frost Phase Diagram A graphical way to summarize the conditions under which equilibrium exists between different states of matter. Allows you to predict the phase of a substance that is stable at a given temperature and pressure Phase Diagram A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas.  Each region on diagram represent a pure phase (solid, liquid, or gas/vapor)  Line between two regions indicates conditions under which two phases (states of matter) can exist in equilibrium (at the same time).  The point at which all three curves meet is called the triple point.  The triple point is the only condition under which all three phases (solid, liquid, and gas) exist at the same time.  The normal boiling point is the temperature at which the liquid boils when the external pressure is 1 atm. The normal melting point is the temperature at which solid melts when the external pressure is 1 atm. Phase Diagram for CO2 At 1 atmosphere and room temperature (250C), would you expect solid carbon dioxide to melt to the liquid phase, or sublime to the gas phase?  Written Work 3! Answer the questions below in relation to the following generic phase diagram. 1. Which section represents the solid phase? ________ 2. What section represents the liquid phase? ________ 3. What section represents the gas phase? ________ 4. What letter represents the triple point? ________ In your own words, what is the definition of a triple point? 5. What is this substance’s normal melting point, at 1 atmosphere of pressure? ________  Written Work 3! Answer the questions below in relation to the following generic phase diagram. 6. What is this substance’s normal boiling point, at 1 atmosphere of pressure? _________ 7. Above what temperature is it impossible to liquefy this substance, no matter what the pressure? _____ 8. At what temperature and pressure do all three phases coexist? ___________________ 9. At a constant temperature, what would you do to cause this substance to change from the liquid phase to the solid phase? _____________________________________________________________ 10 What does sublimation mean? ____________________________________________________ _____________________________________________________________________________