Chemistry & Physics: States of Matter and Changes of State PDF

States of Matter and Changes of States Chemistry & Physics Chapter 7 – States of Matter and Changes of State objectives } } } } } } } } } States of Matter/Changes of States Intermolecular forces Surface tension Surfactants Vapor pressure Clausius-Clapeyron equation Mole fraction/partial pressure Boi...

States of Matter and Changes of States Chemistry & Physics Chapter 7 – States of Matter and Changes of State objectives } } } } } } } } } States of Matter/Changes of States Intermolecular forces Surface tension Surfactants Vapor pressure Clausius-Clapeyron equation Mole fraction/partial pressure Boiling point Changes of State } } Heat of vaporization Phase diagram States of Matter SOLIDS } } } } } Have a definite Volume and Shape Have movement – Vibrate Molecules are touching and do not separate Held in place by intermolecular forces Non-compressible LIQUIDS } } } } } Have a definite Volume but no shape Conform to the shape of their container Molecules are also touching but have more movement Intermolecular forces are weaker and allow the molecules to slide past one another Non-compressible GASES } } } } } Have no definite volume or shape Expand to fill the container Molecules are not touching and have more movement No Intermolecular forces Compressible Changes of States Changes of State Heat of fusion = amt. of E necessary to melt a solid into liquid phase Heat of vaporization = amt. of E necessary to vaporize a liquid into gas phase Note: Heat is the amount of energy flowing into an object, not the same as Temperature. Ex: A sample of ice starting at -40C (ΔHfus = 334J/g, ΔHvap = 2,260J/g) Changes of States Melting – Solid to Liquid state Temp. As more Heat energy is added, vibration between particles becomes greater until the movement overcomes the intermolecular forces holding the molecules together, causing dissociation into a liquid state Changes of States Vaporization – Liquid to Gas state Temp. If we continue to add more heat energy, the movement continues to increase overwhelming the intermolecular forces and particles begin to escape the liquid surface vaporizing into a gas Intermolecular Forces } } } } } Determine how molecules interact with one another Are electrostatic in nature Based on electron organization of the particles Atoms tend to either gain, lose or share electrons in order to achieve a total of 8 valence electrons – like the noble gases The closer an element is to noble gas, the more reactive it is (electronegative) Intermolecular Forces – 3 Types } Dipole-dipole, ex: acetone } } } *Hydrogen bonding, ex. Water } } } } Polar molecule Boiling point 56C, liquid @ room temp. Polar molecule Strongest type of dipole bond Boiling point 100C, liquid @ room temp. London dispersion forces, ex: CH4 } } } Non-polar molecule Weakest type of intermol. bond Boiling pt. -164C, gas @ room temp. Lewis Structure Non-mathematical model that can be used in chemistry to describe chemical bonds using valence electrons. Straight lines represent shared pairs of electrons. Dots represent lone pairs of electrons. Oxygen has 6 valence e- but gains 2 more from 2 hydrogens for a total of 8, like it’s nearest noble gas Ne. Hydrogen has one valence e-, but gains another from oxygen for a total of 2 like it’s nearest noble gas He. Types of Bonds IONIC } } } One atom donates electron to another Ex: Na+ and Cl- = NaCl Usually a metal donating an e- to a non-metal COVALENT } } } Atoms share electrons Ex: H+ and O-- = H2O Ex. H-H bond enthalpy = 436 kj/mol vs. NaCl enthalpy of 131 kj/mol Ionic Bond – example: NaCl Covalent Bond – example: H2O Shared electrons spend more time around the more electronegative atom, leading to a polar covalent bond. *Hydrogen Bonding } } } Occurs when a H atom is bonded directly to O, N or F. H left as a focused point of partial positive charge. Example: Hydrogen Bonding of Water Surface tension Water molecules are attracted to other water molecules. On a surface this causes side-to-side and downward attraction forces, but no balancing attractions from above the surface of the liquid. This unbalanced force creates a “skin” on the surface of the liquid. Example: a drop of water on a freshly waxed car. Water is highly polar and sticks to itself; wax is non-polar. Surfactant Lowers Surface Tension Surface tension poses a potentially significant problem in the Lungs. The thin film of fluid lining the aveloli could cause the walls to stick together and collapse. Surfactant reduces the surface tension so this does not happen. Surface Tension & Surfactant in Lung Inhaled Anesthetics absorbed here Inhaled anesthetics come in LIQUID form Changes states from liquid to vapor via VAPORIZERS Basic concept of vaporization Vaporizers Vapor Pressure } } } } } When molecules of a liquid escape into the gas phase, they collide with the walls of the container, exerting a force on the walls. This is called Vapor Pressure. An increase in temperature causes an increase in Vapor Pressure and in “Volatility”. Volatility is the tendency of a liquid to change into gas. Higher volatility = higher evaporation (ie. ROH vs. H2O) Higher volatility = higher vapor pressure Vapor Pressure of Water and Ethanol Ethanol is more volatile than water at the same temperatures Vapor Pressure of Inhaled Anesthetics Vapor Pressure of Inhaled Anesthetics Vapor pressure is directly correlated with temperature. Increasing temperature will increase the ratio of gas:liquid molecules, thereby increasing vapor pressure. Vapor pressure of volatile agents at 20 degrees C (mmHg): Sevoflurane: 157 Desflurane: 669 Isoflurane: 238 Enflurane: 172 Halothane: 243 N2O: 38,770 Vapor Pressure of Inhaled Anesthetics Boiling point is defined as the temperature at which vapor pressure equals atmospheric pressure (760mmHg). Boiling point (C) Sevoflurane: 58.5 Desflurane: 22.8 Isoflurane: 48.5 Enflurane: 56.5 Halothane: 50.2 N20: -88 Clausius-Clapeyron Equation } } } } } } } } } } Relates Vapor Pressure to Temperature Ln(P) = - ∆Hvap * 1 + C R T P = vapor pressure ∆Hvap = the heat of vaporization (the amount of energy necessary to liberate one mole of liquid into gas phase) R = 8.31 (universal gas constant) T = temperature in Kelvin C = a constant # of the liquid being measured The above equation can be simplified to: logP = A + B/T logP = A + B/T } } } } } } } } This equation is used to calculate the Vapor Pressure of a liquid A and B depend on the particular liquid Ex: For enflurane, A = 7.967 torr, B = -1678 torr K What is the vapor pressure of enflurane at 25C? logP = 7.967 + -1678 / 298 K logP = 2.34 (now need to take the antilog to solve for P) On your calculator, antilog is “10x” or “Xy” = Vapor Pressure of Inhaled Anesthetics logP = A + B/T } } } } This equation is used to calculate the Vapor Pressure of a liquid A and B depend on the particular liquid Ex: For sevoflurane, A = 8.087 torr, B = -1726 torr K What is the vapor pressure of sevoflurane at 20C? Vapor Pressure of Inhaled Anesthetics Vapor Pressure } Vapor Pressure determines the (mole fraction, or) Partial Pressure of a volatile anesthetic in a gas mixture } Ex: If O2 is sent through a vaporizer with liquid sevoflurane, the composition of the O2 sevoflurane mixture will depend on the temp. of the vaporizer and the pressure of the O2. } (The amount of O2 diverted into the vaporizer also influences the mix, but is rate dependent, not thermodynamic) EXAMPLE – find mole fraction of sevoflurane } } } } } } We run O2 at 760 torr through a vaporizer so that it becomes saturated with sevoflurane. In this case, we are at room temp. 20C; the partial pressure of sevoflurane will be the vapor pressure of sevoflurane at that temp. The pressure of the mixture is still 760 torr, but part of this is now composed of sevoflurane. The mole fraction is calculated as follows: Xsevoflurane = vapor pressure of sevoflurane = 157 torr total pressure 760 torr = EXAMPLE – find mole fraction of isoflurane } } } } } } We run O2 at 760 torr through a vaporizer so that it becomes saturated with isoflurane. In this case, we are at room temp. 20C; the partial pressure of isoflurane will equal the vapor pressure of isoflurane. The pressure of the mixture is still 760 torr, but part of this is now composed of isoflurane. Calculate the mole fraction for isoflurane: Xisoflurane = vapor pressure of isoflurane = 238 torr total pressure 760 torr = Dalton’s Law in Practice } } } } } } } If isoflurane is added to a flask of oxygen, what is the % O2 and % isoflurane in the flask above the liquid? Vapor pressure of isoflurane = 238mmHg PO2 after isoflurane is added = (760 – 238) = 522mmHg %O2 = 522 x 100% = 68.7% 760 %iso = 238 x 100% = 31.3% 760 Dalton’s Law in Practice } If enflurane is added to a flask of oxygen, what is the % O2 and % enflurane in the flask above the liquid? Dalton’s Law in Practice } If desflurane is added to a flask of oxygen, what is the % O2 and % desflurane in the flask above the liquid? Boiling Point } Boiling point is the temperature at which the vapor pressure is equal to the ambient pressure (normally one atmosphere). } Boiling point of a liquid will increase if the pressure on the liquid is increased. } Ex: Water normally boils into steam at 100C, but in a sealed pressurized autoclave, the boiling point increases to 120C or more. Phase Diagram Shows the combined effects of temperature and pressure on the state of matter. Ex: phase diagram of water. Interactive Models } Electron Bonding Models } Molecule Polarity Model } States of Matter