Chapter 13 – States of Matter Understanding how the particles are arranged in a substance allows us to predict the physical and chemical properties of a substance. In this unit, we will exam how the particles are arranged in gases, liquids, and solids. We will also discuss various aspects of the phases changes between the three states of matter.

States of Matter Gases Properties

States of Matter Gases Kinetic Molecular Theory – 5 assumptions made about the nature of gas particles. 1.Gas particles move in straight-line paths until they collide with another particle or hit the side of the container wall.

States of Matter Gases Kinetic Molecular Theory – 5 assumptions made about the nature of gas particles. 2. Collisions between gas particles are ‘elastic collisions’. They is no energy transferred between them when they collide. Imagine two bouncy-balls colliding.

States of Matter Gases Kinetic Molecular Theory – 5 assumptions made about the nature of gas particles. 3. The volume of the gas particle is insignificant to the volume of the container it occupies

States of Matter Gases Kinetic Molecular Theory – 5 assumptions made about the nature of gas particles. 5. No attractive or repulsive forces exist between the gas particles.

Pressure Pressure = Force Applied / Area (P = F / A) When the gas molecules collide with the inside wall of the container, it exerts a force over an area. Therefore there is always an internal pressure on a gas.

Measuring Pressure Pressure can be measured using a device called a manometer.

Measuring Pressure Atmospheric Pressure can be measured using a device called a barometer.

Units for Measuring Pressure Pascal (Pa) – Metric System unit for pressure Atmosphere (atm) Pounds per square inch (psi) Torricelli (torr) Millimeter of Mercury (mm Hg) 1 atm = 101,300 Pa = kPa = 14.7 psi = 760 torr = 760 mm Hg

Pressure Conversions 1 atm = 101,300 Pa = kPa = 14.7 psi = 760 torr = 760 mm Hg Convert 0.75 atm into mm Hg. Convert 32.0 psi into kPa.

Liquids The particles of a liquid have more kinetic energy (velocity) than in a solid. The intemolecular forces have been reduced to the increased kinetic energy of the particles.

Liquids Properties of Liquids

Liquids Evaporation – The process of a liquid attaining enough kinetic energy to overcome the intermolecular forces within the liquid to escape to the gas phase.

Liquids Condensation – The process of a liquid losing kinetic energy so that the intermolecular forces within a liquid can capture the gas particle.

States of Matter Vapor Pressure The pressure exerted by the gas above a liquid once dynamic equilibrium has been established between the liquid molecules and gas molecules.

States of Matter Vapor Pressure Dynamic Equilibrium – The rate of evaporation equals the rate of condensation.

States of Matter Vapor Pressure vs Intermolecular Forces The stronger the IMF’s, the more difficult it is for a molecule to escape to the gas phase. Therefore its vapor pressure will be lower. The weaker the IMF’s, the higher the vapor pressure.

States of Matter Vapor Pressure

States of Matter Vapor Pressure and Boiling Point Boiling Point - When the vapor pressure of a liquid becomes equal to the atmospheric pressure.

States of Matter Vapor Pressure and Boiling Point NameBoiling Point (°C) Carbon disulfide (CS 2 )46.0 Chloroform (CHCl 3 )61.7 Methanol (CH 3 OH)64.7 Tetrachloromethane (CCl 4 )76.8 Ethanol (CH 3 CH 2 OH)78.5 Water (H 2 O)100.0

States of Matter Properties of Liquids o Viscosity – The measure of the resistance of a liquid to flow.

States of Matter Properties of Liquids o Viscosity – Affect by temperature and molecular weight.  Temperature – IMF’s are overcome with higher temperature.  Molecular Weight – The larger the molecule, the more ‘tangled’ it becomes, thus resisting flow.

States of Matter Properties of Liquids o Surface Tension – A measure of the inward forces that must be exerted to overcome to expand the surface of a liquid.

States of Matter Properties of Liquids o Surface Tension – Cohesive vs Adhesive Forces  Cohesive Forces – Forces among molecules in a liquid due to IMF’s.  Adhesive Forces – Forces between the molecules of a substance and the surface of a material.

States of Matter Solids Amorphous Solids: Solids that lack any molecular organization.

States of Matter Solids Crystalline Solids: – Solids that have a high degree of molecular organization. – Crystals are three-dimensional shapes that have flat surfaces and angled corners.

States of Matter Solids Crystalline Solids: Geodes

States of Matter Solids Crystalline Solids: – Unit Cells: The repeating three-dimensional shape of a crystalline solid. – Crystal Lattice: Many unit cells making an overall crystal.

States of Matter Solids Crystalline Solids: – All ionic compounds can be explained with 7 different types of unit cells. – We will take a close look at 3 common types; primitive cubic, body-centered cubic, and face-centered cubic.

States of Matter Crystalline Solids Primitive Cubic

States of Matter Crystalline Solids Body-Centered Cubic

States of Matter Crystalline Solids

States of Matter Crystalline Solids  Close Packing Spheres

States of Matter Crystalline Solids  Coordination Number – The number of particles that surround one specific particle in solid.

States of Matter Crystalline Solids  Coordination Number – What is the coordination numbers for the following examples?

States of Matter Covalent Network Solids  Molecular substances in which all of the atoms are connected by a network of covalent bonds.

States of Matter Covalent Network Solids  Diamonds versus graphite

States of Matter Network Solids  Hollow Spheres  Rice University (1985): A 60-Carbon hollow ball of carbon is discovered.

States of Matter Network Solids  Hollow Spheres  These structures were called buckminsterfullerenes or ‘buckyballs’.  Buckminster Fuller: Architect who created geodome shapes.

States of Matter Network Solids  Hollow Spheres  These structures were called ‘buckyballs’.  Buckminster Fuller: Architect who created geodome shapes.

States of Matter Network Solids  Hollow Spheres  Buckyballs are found in nature and even been identified in deep outer space in clouds surrounding stars.

States of Matter Network Solids  Hollow Spheres  Buckyballs have potential uses in medicine, lubricants, and computers.

States of Matter Network Solids  Buckminsterfullerenes  Nanotubes

States of Matter Phase Changes – (A change in the state of matter)

States of Matter Phase Diagrams – Shows the relationship between the temperature and pressure on the state of a substance.

States of Matter Triple Point – The combination of temperature and pressure in which a substance will exist as a solid, liquid, and a gas in dynamic equilibrium.

States of Matter Critical Temperature– The temperature at which a substance can longer be liquified with an increase in pressure.