Kintetic Molecular Theory The invisible motion of still objects - Ran Tivony 4:43 Phases of Matter Kintetic Molecular Theory States of Matter Particle animation

Phases of Matter Gas total disorder highly compressible low density fills container completely assumes shape of container rapid diffusion high expansion on heating molecules are all translating, rotating and vibrating

Phases of Matter Liquid disorder slightly compressible high density does not expand to fill container has definite volume assumes shape of container slow diffusion low expansion on heating particles are rotating and vibrating

Phases of Matter Crystalline Solid p396-399 ordered arrangement slightly compressible high density rigidly retains its volume has definite volume retains its own shape extremely slow diffusion; diffusion only at surfaces low expansion on heating particles are vibrating

Intermolecular Forces According to the Kinetic-Molecular Theory of Matter – the state of a substance at room temperature depends on the strength of the attraction between its particles (intermolecular forces). Attractive Force at Room Temp. State of Matter strong moderately strong weak

Intermolecular Forces According to the Kinetic-Molecular Theory of Matter – the state of a substance at room temperature depends on the strength of the attraction between its particles (intermolecular forces). Attractive Force at Room Temp. State of Matter strong solid moderately strong liquid weak gases

At different temperatures the particles/molecules have different kinetic energy. Example: Water Below 0°C - Water is a solid because there is not enough kinetic energy to overcome the attractive forces. (Normal Freezing Point of water = 0°C => temperature at which substance changes to the solid phase)

Above 0°C - Molecules have enough kinetic energy to "get away" from each other and flow. (Normal Melting Point of water = 0°C => temperature at which substance changes to the liquid phase)

Above 100°C - Average kinetic energy is so high the molecules are able to "escape" from each other to fill the entire space available to them. (Normal Boiling Point of water = 100°C => temperature at which substance changes to the gas phase)

Chemical Bonding (Intramolecular Forces) vs. Intermolecular Forces Ionic Bonding - transfer of electrons Covalent Bonding - sharing of electrons Metallic Bonding - metallic substances share their valence electrons among themselves in a "sea of electrons“

Intermolecular Forces - forces of attraction between neighboring molecules. Intermolecular Forces are important in determining the physical properties of substances – ie. melting point, boiling point, solubility

Compared to the strength of intramolecular forces, intermolecular forces are substantially weaker. For example, it takes 463 kilojoules to break one mole of O-H bonds, but only 6 kilojoules to melt a mole of ice into water and 41 kilojoules to convert a mole of water to steam.

Types of Intermolecular Forces The boiling point and the melting point of a substance depend on the strength of the intermolecular forces. The stronger the attractive force the higher the boiling point and the melting point temperature.

Properties of Liquids p390 The physical properties of liquids are determined by the nature and strength of the intermolecular forces present between their molecules.

the greater the viscosity. Viscosity - the friction or resistance to motion that exists between molecules of a liquid when moving past each other. The stronger the intermolecular attraction between molecules of a liquid, The greater the resistance to flow → the greater the viscosity. Viscosity increases as temperature decreases. At lower temperatures the speed of the molecules decreases.

Properties of CRYSTALLINE SOLIDS p396-399 Particles in the solid state, (which may be atoms, molecules or ions) – are not free to move away from each other. CRYSTALLINE SOLID - particles exist in a highly ordered repeating pattern called the crystal lattice structure. (geometric structure) see figures 13-4 & 13-5 p399

AMORPHOUS SOLIDS – substances that are rigid and appear solid but are not arranged in a crystal lattice structure. They are highly viscous, super-cooled liquids, but are not true solids. examples – Glass, Plastics Highly viscous liquids have a high resistance to flow because of strong intermolecular forces. The physical properties of solids, such as hardness, electrical conductivity, and melting point depend on the kind of particles that make up the solid and on the strength of the attractive forces between them. 4:38 What is metallic glass? - Ashwini Bharathula TED Ed 4:43

Forces Between Particles Properties Examples Type of Solid (type of particles) Forces Between Particles Properties Examples Metallic (atoms)  metallic bond soft to hard, low to high melting point, good conductors of heat & electricity, malleable and ductile  all metallic elements – Al, Cu, Na, Ag, Fe…. Molecular (atoms, molecules)  hydrogen bond, dipole-dipole, dispersion soft, low melting point, poor conductors of heat & electricity   organic compounds – CS2, C12H22O11 inorganic compounds – H2O  Ionic (positive and negative ions)  electrostatic attraction hard, brittle, high melting point, poor conductors of heat & electricity typical salts – NaCl, KBr, MgSO4 Network Covalent (atoms)  covalent bonds very hard, very high melting point, often poor conductors of heat & electricity diamond, C; graphite,C; silicon, Si; silicon dioxide, SiO2