KINETIC THEORY Unit 7 Chemistry Langley Corresponds to

KINETIC THEORY Unit 7 Chemistry Langley *Corresponds to Chapter 13 (pgs. 384 -409) in Prentice Hall Chemistry textbook

KINETIC THEORY § Kinetic Theory states that the tiny particles in all forms of matter are in constant motion. § Kinetic refers to motion § Helps you understand the behavior of solid, liquid, and gas atoms/molecules as well as the physical properties § Provides a model behavior based off three principals

KINETIC THEORY § 3 Principles of Kinetic Theory § All matter is made of tiny particles (atoms) § These particles are in constant motion § When particles collide with each other or the container, the collisions are perfectly elastic (no energy is lost)

STATES OF MATTER § 5 States of Matter § Solid § Liquid § Gas § Plasma § Bose-Einstein Condensates http: //www. plasmas. org/E-4 phases 2. jpg

SOLIDS § § § Particles are tightly packed and close together Particles do move but not very much Definite shape and definite volume (because particles are packed closely and do not move) § Most solids are crystals § Crystals are made of unit cells (repeating patterns) § The shape of a crystal reflects the arrangement of the particles within the solid

SOLIDS § Unit cells put together make a crystal lattice (skeleton for the crystal) § Crystals are classified into seven crystal systems: cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, rhombohedral § Unit cell crystal lattice solid

SOLIDS § Amorphous Solid: § A solid with no defined shape (not a crystal) § A solid that lacks an ordered internal structure § Examples: Clay, Play. Doh, Rubber, Glass, Plastic, Asphalt § Allotropes: § Solids that appear in more than one form § 2 or more different molecular forms of the same element in the same physical state (have different properties) § Example: Carbon § § § Powder = Graphite Pencil “lead” = graphite Hard solid = diamond

SOLIDS www. ohsu. edu/research/sbh/resultsimages/crystalvsglass. gif

SOLIDS Allotropes of Carbon: a) diamond, b) graphite, c) lonsdaleite, d)buckminsterfull erene (buckyball), e) C 540, f) C 70, g) amorphous carbon, and h) single-walled (buckytube) www. wikipedia. org

LIQUIDS § § § Particles are spread apart Particles move slowly through a container No definite shape but do have a definite volume Flow from one container to another Viscosity – resistance of a liquid to flowing § Honey – high viscosity § Water – low viscosity chemed. chem. purdue. edu/. . . /graphics

GASES § § § Particles are very far apart Particles move very fast No definite shape and No definite volume http: //www. phy. cuhk. edu. hk/contextual/heat/tep/ trans/kinetic_theory. gif

PLASMA § § § Particles are extremely far apart Particles move extremely fast Only exists above 3000 degrees Celsius Basically, plasma is a hot gas When particles collide, they break apart into protons, neutrons, and electrons § Occurs naturally on the sun and stars

BOSE-EINSTEIN CONDENSATE § § § Particles extremely close together Particles barely move Only found at extremely cold temperatures § Basically Bose-Einstein is a cold solid § Lowest energy of the 5 states/phases of matter

GASES AND PRESSURE § Gas pressure is the force exerted by a gas per unit surface area of an object § Force and number of collisions § When there are no particles present, no collisions = no pressure = vacuum § Atmospheric Pressure is caused by a mixuture of gases (i. e. the air) § Results from gravity holding air molecules downward in/on the Earth’s atmosphere; atmospheric pressure decreases with altitude, increases with depth § Barometers are devices used to measure atmospheric pressure (contains mercury) § Standard Pressure is average normal pressure at sea level § As you go ABOVE sea level, pressure is less § As you go BELOW sea level, pressure is greater

GASES AND PRESSURE § Standard Pressure Values § At sea level the pressure can be recorded as: § § § 14. 7 psi (pounds per square inch) 29. 9 in. Hg (inches of Mercury) 760 mm. Hg (millimeters of Mercury) 760 torr 1 atm (atmosphere) 101. 325 k. Pa (kilopascals) § All of these values are EQUAL to each other: § § 29. 9 in. Hg = 101. 325 k. Pa 760 torr = 760 mm. Hg 1 atm = 14. 7 psi and so on………. § Say hello to Factor Label Method!!!!!!

GASES AND PRESSURE § STP § Standard Temperature and Pressure § Standard Pressure values are the values listed on the previous slides § Standard Temperature is 0°C or 273 K § If temperature is given to you in Farenheit, must convert first! § °F = (9/5)°C + 32 § °C = (5(°F-32)) / 9 Remember order of operation rules § K = 273 + °C § °C = K – 273

GASES AND PRESSURE § Pressure Conversions § Example 1: 421 torr = ? Atm § Step 1: Write what you know § Step 2: Draw the fence and place the given in the top left § Step 3: Arrange what you know from step 1 such that the nondesired units canceling out so that you are only left with the units you want (i. e. atm) § Step 4: Solve § Step 5: Report final answer taking into account the appropriate significant figures

GASES AND PRESSURE § Pressure Conversions § Example 2: 32. 0 psi = ? torr

TEMPERATURE § Temperature is the measure of the average kinetic energy of the particles. § 3 Units for Temperature: § Celsius § Farenheit § Kelvin § Has an absolute zero § Absolute lowest possible temperature § All particles would completely stop moving § Temperature Conversions: § Example 1: Convert 35°C to °F § Example 2: Convert 300 Kelvin to °C

MEASURING PRESSURE § Manometers: § Measure pressure § 2 kinds: open and closed § Open Manometers: § Compare gas pressure to air pressure § Example: tire gauge § Closed Manometer: § Directly measure the pressure (no comparison) § Example: barometer

KINETIC ENERGY AND TEMPERATURE § § § Energy of motion Energy of a moving object Matter is made of particles in motion Particles have kinetic energy KE = (mv 2)/2 OR KE = (ma)/2 § Kinetic Energy is measured in Joules § 1 J = 1 kg • m 2/s 2 § The mass must be in kg § The velocity must be in m/s OR acceleration must be in m 2/s 2

KINETIC ENERGY AND TEMPERATURE § Calculate the KE of a car with a mass of 1500 kg and a speed of 50 m/s

KINETIC ENERGY AND TEMPERATURE § Calculate the KE of a car with a mass of 6780 grams and a speed of 36 km/h

KINETIC ENERGY AND TEMPERATURE § Temperature-measure of the average kinetic energy of the particles § Kelvin Scale: § Has an absolute zero (0 K) § Absolute lowest possible temperature § In theory, all particles would completely stop moving § Speed of Gases: § If two gases have the same temperature (particles moving at the same speed) how can you tell which gas has a greater speed? § The only difference is mass! § To find mass, use the periodic table

KINETIC ENERGY AND TEMPERATURE § Speed of Gases § Example 1: If CH 4 and NH 3 are both at 284 K, which gas has a greater speed? § Step One: Add up the mass of each gas using the periodic table. § Step Two: The lighter gas moves faster (think about a race between a 100 -pound man and a 700 -pound man, the lighter man would move faster) § Example 2: Which gas has a faster speed between Br 2 and CO 2 if both are at 32°F?

TERMINOLOGY for PHASE CHANGES § Melting-commonly used to indicate changing from solid to liquid § Normal melting point-The temperature at which the vapor pressure of the solid and the vapor pressure of the liquid are equal § Freezing-Changing from a liquid to a solid § Melting and freezing occur at the same temperature § Liquifaction-Turning a gas to a liquid § Only happens in low temperature and high pressure situations

TERMINOLOGY for PHASE CHANGES § Difference in Gas and Vapor § Gas-state of matter that exists at normal room temperature § Vaport-produced by particles escaping from a state of matter that is normally liquid or solid at room temperature § Boiling-used to indicate changing from a liquid to a gas/vapor § Normal boiling point - temperature at which the vapor pressure of the liquid is equal to standard atmospheric pressure, which is 101. 325 k. Pa § Boiling point is a function of pressure. § At lower pressures, the boiling point is lower

TERMINOLOGY for PHASE CHANGES § 2 types of boiling: boiling and evaporation § Evaporation takes place only at the surface of a liquid or solid while boiling takes place throughout the body of a liquid § Particles have high kinetic energy § Particles escape and become vapor § Condensation-used to indicate changing from a vapor to a liquid

TERMINOLOGY for PHASE CHANGES § Sublimation - when a substance changes directly from a solid to a vapor § The best known example is "dry ice", solid CO 2 § Deposition-when a substance changes directly from a vapor to a solid (opposite of sublimation) § Example-formation of frost § Dynamic equilibrium - when a vapor is in equilibrium with its liquid as one molecule leaves the liquid to become a vapor, another molecule leaves the vapor to become a liquid. An equal number of molecules will be found moving in both directions § Equilibrium - When there is no net change in a system

TERMINOLOGY for PHASE CHANGES § Points to Know: § Melting Point-Temperature when solid turns to a liquid § Freezing Point-Temperature when liquid turns to a solid § Boling Point-Temperature when a liquid turns to a vapor § Doesn’t boil unitl vapor pressure coming off liquid is equal to the air pressure around it § Since air pressure changes with height, water does not always boil at 100°C § Condensing Point-Tempeature when vapor turns to liquid

ENTROPY § A measure of the disorder of a system § Systems tend to go from a state of order (low entropy) to a state of maximum disorder (high entropy) § Entropy of a gas is greater than that of a liquid; entropy of a liquid is greater than that of a solid § Solids=low entropy; plasma=high entropy § Entropy tends to increase when temperature increases § As substances change from one state to another, entropy may increase or decrease

Le CHATELIER’S PRINCIPLE § Anytime stress is placed on a system, the sytem will readjust to accommodate that stress § If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or total pressure, then the equilibrium shifts to partially counteract the imposed change § Can be used to predict the effect of a change in conditions on a chemical equilibrium § Is used by chemists in order to manipulate the outcomes of reversible reactions, often to increase the yield of reactions

Le CHATELIER’S PRINCIPLE § When liquids are heated (stress) they produce vapor particles (adjust) § When liquids are cooled (stress) the particles inside tighten to form a solid (adjust)

Le CHATELIER’S PRINCIPLE § Le Chatelier’s Principle explaining boiling and condensation using covered beaker partially filled with water § At a given temperature the covered beaker constitutes a system in which the liquid water is in equilibrium with the water vapor that forms above the surface of the liquid. § While some molecules of liquid are absorbing heat and evaporating to become vapor, an equal number of vapor molecules are giving up heat and condensing to become liquid. § If stress is put on the system by raising the temperature, then according to Le Châtelier's principle the rate of evaporation will exceed the rate of condensation until a new equilibrium is established

PHASE DIAGRAMS § A diagram showing the conditions at which substance exists as a solid, liquid, or vapor § Shows the temperature and pressure required for the 3 states of matter to exist § Conditions of pressure and temperature at which two phases exist in equilibrium are indicated on a phase diagram by a line separating the phases § Draw the phase diagram for water

PHASE DIAGRAM-WATER

PHASE DIAGRAM-WATER § Explanation of Phase Diagram: § X axis-Temperature (°C) § Y axis- Pressure (k. Pa) § Line AB – line of sublimation § Line BD – boiling point line § Line BC – melting point line § Point B – triple point (all 3 states of matter exist at the same time) § Tm – melting point at standard pressure § Tb – boiling point at standard pressure

HEAT in CHANGES of STATE § Energy Diagrams (also referred to as Heating Curves) § Graphically describes the enthalpy (the heat content of a system at sonstant pressure) changes that take place during phase changes § X axis is Energy (Heat supplied) § Y axis is Temperature

HEAT in CHANGES of STATE § Constructing Energy Diagrams § Step 1: Determine/Identify the melting and boiling points for the specified substance § Step 2: Draw x and y axis (energy vs temp) § Step 3: Calculations § § § First diagonal line: Q = mc. DT First horizontal line: Q = m. Hf Second diagonal line: Q = mc. DT Second horizontal line: Q = m. Hv Third horizontal line: Q = mc. DT Add up all values!!! § Draw the energy diagram for 10 grams of water as it goes from – 25°C to 140°C