Presentation on theme: "Chapter 6: The States of Matter"— Presentation transcript:
1Chapter 6: The States of Matter Suggested Problems:
2States of Matter ______ _______ Definite volume and shape Definite volume but not shapeTakes the shape of its container_______No definite volume or shapeWill not only take the shape of its container it will fill it completely
3Solids A __________ state of matter Atoms (or molecules) are “touching”Strongest intermolecular forcesHold atoms (or molecules or ions, etc.) rigidly in a 3D crystalline lattice
4Liquids Also a __________ state of matter Atoms (or molecules) are “touching”Intermolecular forces hold atoms (or molecules) in contact, but not rigidly in place…molecules can slide past each other
5Gases Virtually ___ intermolecular forces Gaseous molecules (etc.) comprise a very small percent of the sample volumeGaseous molecules are in constant random motion…the velocity is related to temperatureMolecules collide with walls of container and with each other and bounce off with no loss of energy
6Properties of GasesGases are the best understood state of matter, because we ignore intermolecular forcesThe volume a gas sample occupies is a function of three variables:___________
7Pressure Pressure is force per unit area Units of pressure: Pounds per square inchTorr or mmHgAtmosphere1 atm = 760 torr = 760 mmHg = 14.7 psi
8Measuring Pressure: Barometer gravity pulling downair pushing down
9Pressure Conversion Example The gauge on an oxygen gas cylinder reads 1272 psi. Express this in atm and torr. (1 atm=14.7 psi)
10Volume of a GasImagine a fixed amount of air at a given temperature and pressure in a balloonWhat will happen to the volume if we add more air?
11Volume of a GasImagine a fixed amount of air at a given temperature and pressure in a balloonWhat will happen to the volume if we squeeze the balloon (increase pressure)?
12Volume of a GasImagine a fixed amount of air at a given temperature and pressure in a balloonWhat will happen to the volume if we increase the temperature?
13The Combined Gas Law P is pressure V is volume T is ________ temperaturen is number of moles
14The Empirical Gas Laws Boyle’s Law Charles’s Law Avogadro’s Law Volume is inversely proportional to pressure (constant n and T)Charles’s LawVolume is directly proportional to the Kelvin temperature (constant n and P)Avogadro’s LawThe volume of a gas is directly proportional to the number of gas moles (constant T and P)
15Boyle’s Law: Example15 liters of argon is collected at an initial pressure of 1.05 atm. If the gas is compressed to a new pressure of 1510 torr, what is the new volume?
16Charles’s Law: Example The temperature of 35.6 mL of neon is increased from –35.4ºC to 75.2ºC. What is the new volume?
17Combining Boyle’s and Charles's Laws A bubble of air having a volume of 75.0 mL is released from 35 feet under the sea (where the pressure is 2.07 atm and the temperature is 18 ºC). What will the new volume be at the surface, where P=0.967 atm and T=23 ºC?
18The Ideal Gas LawCombines the elements of the ________ gas laws
19Standard Conditions STP = standard temperature and pressure T = _____ K (_____ ºC)P = _____ atm = ____ torr
20ExampleWhat volume will 2.0 grams of helium occupy at a temperature of 290K and a pressure of 800 torr?
21Which Gas Law to Use?Use the combined gas law when the problem describes two sets of conditionsthe pressure and/or temperature changesUse the ideal gas law when there are a single set of conditions
22Dalton’s Law of Partial Pressures The ______ pressure of a gaseous mixture is the sum of the partial pressuresNitrogen0.75 atmOxygen0.25 atmEmptycontainerNitrogen0.75 atmOxygen0.25 atmPtotal =
23Graham’s Law__________ is net movement of a gas from an area of high concentration (pressure) to an area of lower concentration__________ is the movement of a gas through a pinholeBoth Diffusion and Effusion follow Graham’s LawRate is an amount per time
24Graham’s Law ExampleOxygen Molecules weigh 16 times as much as hydrogen molecules. Which molecule will diffuse faster and how much faster?
25What do all of these changes Changes of StateGascondensevaporizesublimecondensefreezeLiquidSolidmeltWhat do all of these changesin state have in common?
26Energy Energy is the ability to do work Kinetic Energy: energy due to motion_________ Energy: stored energyHeat Energy: the sum of the kinetic and potential energies of molecules in a sample
27Energy and Its Unitscalorie (cal): is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius at 15 oCkilocalorie = 1000 calA food Calorie = 1000 calJoules (J): are the metric unit of energy1 cal = J
28Energy Conversion Example A candy bar has 350 Calories. How many joules does one candy bar contain?
29Heat and Temperature__________: is a measurement of the average kinetic energy of the molecules in a sample___ is measured in degrees with a thermometer_______: is the sum of the kinetic (and potential) energies in a sample_____ is measured in calories with a calorimeter
30CalorimetersBomb CalorimeterCoffee Cup Calorimeter
31Specific HeatSpecific heat (SH) is the amount of heat needed to raise the temperature of 1 gram of material by one degree Celsius
32Specific Heat ExampleA 10.0 gram sample of copper at 25 ºC has a final temperature of 100 ºC when 289 J of heat are added. What is the specific heat of copper? (SH of liq water = 4.18 J/goC)
33Distribution of Energy In a sample of material, the kinetic energies of the molecules follow a Boltzman Distribution:Average KE# MoleculesKinetic Energy
34Kinetic Energy Distribution ThighTlow# MoleculesKinetic Energy
35Changes of State Gas Liquid Solid condense vaporize sublime condense freezeLiquidSolidmelt
36VaporizationThe most energetic molecules in a liquid have sufficient kinetic energy to escape into the ____ phaseOnce the molecules are free as gases, they exert a pressureThis is called the ______ pressureHow does vapor pressure depend on temperature?
38Boiling PointThe boiling point of a liquid is the temperature where the vapor pressure equals the ambient pressure.The _______ boiling point of a liquid is the temperature where the vapor pressure equals 760 torr.How does boiling point depend on pressure?
39What do all of these changes Changes of StateGascondensevaporizesublimecondensefreezeLiquidSolidmeltWhat do all of these changesin state have in common?
40Freezing/Melting Point The melting point of a substance is the temperature at which a crystalline solid changes to a liquid.What is the difference between melting point and freezing point?
41Energy Changes and Changes of State Imagine recording the temperature of an 18 gram (i.e., 1.0 mole) sample of ice at -40ºC as heat is addedheat added, kJtemperature0.0-401.57.515.010055.756.5120No TNo T
42Heating Curve for 1 Mole of Water Water is boiling:Heat of vaporization40.7 kJ/molIce is melting:Heat of fusion6.02 kJ/mol
43Molar Heat of FusionDHºfus is the heat required to convert one mole of solid to a liquid at at its normal melting pointDHºfus represents the energy needed to break down intermolecular forces and allow molecules to slide around the liquid phase
44Molar Heat of Vaporization DH°vap is the heat required to convert one mole of liquid to a gas at at its normal boiling pointDH°vap represents the energy needed to break intermolecular forces and allow molecules to escape into the gas phase
45Putting it all Together How much heat is required to convert an 18 gram piece of ice at -40 oC to steam at 120 oC?
46Heating Curve for 1 Mole of Water DEHeat of vaporization40.7 kJ/molCq = m(SH)(T)SH ice = 2.1 J/goCSH liq = 4.18 J/goCSH gas = 2.0 J/goCBHeat of fusion6.02 kJ/molA
47QuestionExplain why orange growers spray their trees with water when there is a threat of freezing temperatures.
48QuestionWhy does steam at 100ºC cause more severe burns than water at the same temperature?