States of Matter & Gas Laws Chapters 13 & 14

STATES OF MATTER & THEIR PROPERTIES What’s the ‘matter’ with you?

Solids Definite shape and volume Will not move (static) to fit container Will not flow Particles are together Low kinetic energy Low entropy - Entropy change has often been defined as a change to a more disordered state

Liquids Indefinite shape, definite volume. Will move to fit container Will flow. In most cases particles are more spread out Particles have higher KE Particles have higher entropy

Gases Indefinite shape, indefinite volume. Will move to fit container Will flow. Particles are spaced wide apart. Very high KE High entropy (chaotic, disordered)

Plasma Electrically charged gas. Will flow High KE High Entropy Ex. lightning

Physical Change When matter changes from solid to liquid or from liquid to solid, it is changing its physical state, therefore it is a physical change or phase change.

PHASE CHANGES MELTING FREEZING VAPORIZATION (boiling) CONDENSATION Solid  Liquid Liquid  Solid Liquid  Gas Gas  Liquid Solid  Gas Gas  Solid MELTING FREEZING VAPORIZATION (boiling) CONDENSATION SUBLIMATION DEPOSITION

PHASE DIAGRAM-Warm Up Pressure Temperature LIQUID PHASE B Pressure SOLID PHASE GAS PHASE A Temperature Label the triple point and critical point on this diagram. How much heat is released if 50 g of liquid water cools from 85˚ C to 20˚C?.

PHASE DIAGRAMS Triple Point: the temperature and pressure at which three phases of a substance can coexist. Critical Point: critical temperature above which no amount of pressure can change the vapor into a liquid. Lines: indicate T and P at which two phases exist in equilibrium

A phase diagram is unique for each substance

Phase Diagram WATER: MP = 0oC BP = 100oC

What phase change occurs when carbon dioxide goes from B to A? Normal MP and BP means at standard pressure. Standard Pressure = 1 atm What phase change occurs when carbon dioxide goes from B to A? FREEZING

Vapor Pressure Vapor Pressure: the pressure exerted by a vapor over a liquid in a closed container. A liquid in a sealed container evaporates until its vapor pressure is high enough that the rates of evaporation and condensation are equal. A substance that evaporates easily has a higher vapor pressure. Add pic

Vapor Pressure Example Ethanol is more volatile than water (evaporates more easily) and therefore has a higher vapor pressure. Ethanol vapors exert more pressure on its container at equilibrium. Water molecules are more polar than ethanol molecules. Why do you think water has a lower vapor pressure compared to ethanol?

Vapor Pressure Concepts (cont’d) Increasing the temperature of a liquid in a closed container increases the vapor pressure. Boiling point: the temperature of a substance when its vapor pressure = atmospheric pressure. Boiling point of a substance increases when the pressure on the liquid increases.

Warm Up for Tuesday, April 30 Hydrogen gas was cooled from 150 C to 30 C. Its new volume is 75 mL. What was its original volume? Fluorine exerts a pressure of 900 torr. When the pressure is changed to 152 kPa, its volume is 250 mL. What was the original volume?

Warm Up P1V1 = P2V2 T1 T2 1. If a tire has a pressure of 32 psi and a volume of 5 L of gas, what would the pressure be if the volume decreases to 3 L? 2. If the temperature of a gas is 275 K and the volume is 5 L, what is its volume at 303 K? 3. Explain the relationship between pressure, volume, and temperature based on Fridays activity

Kinetic Theory of Matter All particles are moving all the time.

Gases No definite shape or volume Easily compressible

What do we know about gas particles? Can be either molecules or atoms; e.g. He, O2, C3H8 Very far apart from one another. Between particles is empty space. No attractive or repulsive forces between particles. Move randomly. Move at high speeds (O2 at 20oC moves at 1700 km/h). Travel in straight paths. Only change direction when collide with another particle/object. Collide elastically (no kinetic energy lost).  Ideal Gas

Gas Pressure The force exerted by a gas per unit of surface area.  Created by the collision of gas particles with a surface.

Vacuum empty space  no particles no pressure A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum https://www.youtube.com/watch?v=E43-CfukEgs

Atmospheric Pressure Atmospheric Pressure: created by the gases that make up Earth’s atmosphere.  Atmospheric pressure decreases as elevation increases (lower density of gases).  Measured using a Barometer.

Units of Pressure SI Unit = pascal (Pa) Other units: atmospheres (atm) millimeters of mercury (mmHg) torr pounds per square inch (psi) Standard Pressure: 101.3 kPa = 1 atm = 760 mmHg = 760 torr = 14.7 lb/in2 (psi) Rmv psi

Temperature Temperature: average kinetic energy of particles The faster the particles are moving, the higher the temperature. Kelvin temperature is directly proportional to the average kinetic energy of the particles of the substance. Particles at 200K have twice the average KE of particles at 100K. Absolute Zero: KE = 0; all motion of particles stops We have only produced 0.5 nanokelvin.  TK = TC + 273

Relative Density of States of Matter GENERAL TREND: In order from most dense to least dense: solid, liquid, gas Exception: Water is most dense at 4oC (liquid).

Gas Laws P1V1 = P2V2 T1 T2 (FOR A FIXED AMOUNT OF GAS) Cool Program Gas Laws (FOR A FIXED AMOUNT OF GAS) P1V1 = P2V2 T1 T2 (COMBINED GAS LAW)

Boyle’s Law Units: Pressure – Volume – Boyle’s Law: At constant temperature, the pressure and volume of a gas are inversely proportional. P1V1 = P2V2 Graph: Units: Pressure – Volume –

Boyle’s Law

Boyle’s Law Math Problems The volume of a gas at 99 kPa is 300 mL. If the pressure is increased to 188 kPa, what will be the new volume? The pressure of a sample of helium in a 1.0-L container is 0.988 atm. What is the new pressure if the sample is placed in a 2.0-L container? *Both Pressures must be in the same unit. Both Volumes must be in the same unit.

Charles’s Law Units: Volume – Temperature – Charles’s Law: At constant pressure, the volume of a gas is directly proportional to its Kelvin temperature. V1 = V2 T1 T2 Graph: Units: Volume – Temperature –

Charles’s Law

Liquid Nitrogen

Charles’s Law The Math… The Celsius temperature of a 3.0-L sample of gas is lowered from 80oC to 30oC. What will be the resulting volume of this gas? A gas at 89oC occupies a volume of 0.67 L. At what Celsius temperature will the volume increase to 1.12 L?

Gay-Lussac’s Law Gay-Lussac’s Law: At constant volume, the pressure of a gas is directly proportional to its Kelvin temperature. P1 = P2 T1 T2

Gay-Lussac’s Law What happens to pressure if temperature increases and volume is held constant? The pressure in an automobile tire is 1.88 atm at 25oC. What will be the pressure if the temperature warms up to 37oC?

Combined Gas Law Combined Gas Law: for a fixed amount of gas. P1V1 = P2V2 T1 T2   STP = 273 K (0 oC), 1 atm

Warm UP A helium-filled balloon at sea level has a volume of 2.1 L at 0.998 atm and 36oC. If it is released and rises to an elevation at which the pressure is 0.9 atm and the temperature is 28oC, what will be the new volume of the balloon? At STP, a sample of gas occupies 30 mL. If the temperature is increased to 30 oC and the entire gas sample is transferred to a 20 mL container what will be the gas pressure in kPa inside the container? A mixture of gases at a total pressure of 95 kpa contains N2, CO2, and O2. Partial pressure of CO2 is 24 kpa and N2 is 48 kPa. What is the partial pressure of the O2?

Ideal Gas Law Amount of Gas Varies PV = nRT P= pressure (atm, mmHg, kPa) V= volume (L) n = number of moles R = 0.0821 L*atm/mol*K = 62.4 L*mmHg/mol*K = 8.31 kPa*L/mol*K (see your reference table!) T=temperature (K) What pressure is exerted by 0.450 mol of a gas at 25oC if the gas is in a 0.650-L container? Determine the volume occupied by 0.582 mol of a gas at 15oC if the pressure is 81.8 kPa.

Ideal Gas Law What pressure is exerted by 0.450 mol of a gas at 25oC if the gas is in a 0.650-L container? Determine the volume occupied by 0.582 mol of a gas at 15oC if the pressure is 81.8 kPa.

Avogadro’s Law Avogadro’s Law n1 = n2 V1 V2

Avogadro’s Law Assuming that pressure and temperature remain constant, what happens to the volume of a gas if the number of moles doubles? If you have two moles of a gas in a 4-liter container, how many moles of the gas would you have to release in order for the gas to occupy a 3- liter container and retain the same pressure and temperature.

Mixtures of Gases Dalton’s Law of Partial Pressures: the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture. Ptotal = P1 + P2 + P3 + … Partial Pressure of a Gas: the portion of the total pressure contributed by a single gas.

Dalton’s Law of Partial Pressures What is the partial pressure of hydrogen gas in a mixture of hydrogen and helium if the total pressure is 600 mmHg and the partial pressure of helium is 439 mmHg?

Warm up- Pick up the test materials up front Warm up- Pick up the test materials up front! Take out your review guide! Calculate the volume that 0.881 mol of gas at STP will Occupy. If a balloon will rise off the ground when it contains 0.0226 mol of helium in a volume of 0.460L , how many moles of helium are needed to make the balloon rise when its volume is 0.865L? Assume that temperature and pressure stay constant.

After your test… On your scantron: SIDE 1 Name Subject: Gas Laws Date: 5/3/13 #9 – Hint: PTotal = P1 + P2 + …..(be sure they are all in the same units ;) ) Pick up the worksheet up front on phase change diagrams. If you need help, grab a textbook and read the chapter on States of Matter.