Agenda: Thermochemistry Heating & Cooling Curves – a review Graphing temperature change Phase Change Diagrams Why are some compounds liquids and gases at room temperatures ? Homework:

Characteristics of Solids, Liquids & Gases Sort the terms into 3 columns: S, L, G  (Hint: Look for 3 cards with similar wording and determine which best fits solid, liquid or gas) Solid Liquid Gas

Most substances, like water, can exist in all three states. A cloud is made of water vapor, a type of gas. An iceberg is made of water in solid form. This glass contains liquid water.

WHAT ARE THE CHANGES OF STATE? GAS SOLIDLIQUID Deposition Sublimation Boiling / Evaporation Condensation Freezing Melting Which are endothermic? Which are exothermic?

Changing States (Phase changes) Solid Gas Liquid Increase Thermal Energy (Heat up) Decrease Thermal Energy (Cool off) Where on the picture would we place: -Melting Point? -Boiling Point? -Condensing Point? -Freezing Point?

States of matter, energy & phase changes Energy level Energy change Phase changes MP/BP Entropy= degree of disorder

Melting point Melting - change from solid to liquid Melting point - SPECIFIC temperature when melting occurs. Each pure substance has a SPECIFIC melting point.  Examples:  M.P. of Water = 0°C (32°F)  M.P. of Nitrogen = °C ( °F)  M.P. of Silver = °C ( °F)  M.P. of Carbon = °C ( °F)

Melting Point Particles of a solid vibrate so fast that they break free from their fixed positions. Solid Liquid Increasing Thermal Energy Melting point

Vaporization Vaporization – change from liquid to gas Vaporization happens when particles in a liquid gain enough energy to form a gas. Gas Liquid Increasing Thermal Energy Boiling point

Two Kinds of Vaporization Evaporation – vaporization that takes place only on the surface of the liquid Boiling – when a liquid changes to a gas BELOW its surface as well as above.

Boiling Point Boiling Point – temperature at which a liquid boils Each pure substance has a SPECIFIC boiling point.  Examples:  B.P. of Water = 100°C (212°F)  B.P. of Nitrogen = °C ( °F)  B.P. of Silver = 2162 °C (3924 °F)  B.P. of Carbon = 4027 °C (7281 °F)

States of matter, energy & phase changes Energy level Energy change Phase changes MP/BP Entropy= degree of disorder

Heating and Cooling Curves of a Substance Representing MP, BP, CP, FP Heating Cooling Energy (heat) addedEnergy (heat) released:

Energy requirements for water Three formulas : specific heat Q = mC p ∆T heat of fusion Q= mH f heat of vaporization Q= mH v Heating Cooling Energy (heat) addedEnergy (heat) released:

Energy calculations related heating or cooling specific substances Specific heat (C p ) Latent heat Heat of fusion (H f ) Heat of vaporization (H v ) Use reference tables – values for each pure substance

Heat calculations – 3 formulas Specific heat = heat required to raise the temperature of 1 gram of substance 1 °C Formula: Q = mC p ∆T Specific heat  Specific for each pure substance  Use reference tables

Heat calculations – 3 formulas Heat of fusion -  Amount of heat added to melt a substance  Amount of heat released to freeze a substance Formula Q= mH f  Specific for each pure substance  Use reference tables

Heat calculations – 3 formulas Heat of vaporization-  Amount of heat added to boil a substance  Amount of heat released to condense a substance Formula Q= mH v  Specific for each pure substance  Use reference tables

Heat energy In a heat calculation problem, if the problem asks about melting/freezing you would multiply the mass times _____________________.  heat of fusion  heat of vaporization  or specific heat In a heat calculation problem, if the problem asks about vaporizing/condensing of steam, you would multiply the mass times ________.  Heat of fusion  Heat of vaporization  Specific heat In a heat calculation problem, if the problem asks about a change in temperature, you would multiply the mass times ___________________ times the change in temperature.  Heat of fusion  Heat of vaporization  Specific heat

Thermochemistry Problems related to water 1.How much heat is required to raise the temperature of 789 g of water from 25 o C to 70 o C? 2. How much heat is released when 432 g of water cools from 71 o C to 18 o C? 3. How many joules of heat are given off when 5.9 g of steam cools from 175 o C to 125 o C?

4. How many joules does it take to melt 35 g of ice at 0 o C? 5. How much heat is released when 85 g of steam condense to liquid water? 6. How much heat is necessary to raise the temperature of 25 g of water from 10 o C to 60 o C? 7. How much heat is given off when 50 g of water at 0 o C freezes?

How much energy is needed to heat water from a solid to a vapor? Graph the data – using most of the graph paper Time (when heat energy is added) Resulting temperature See Textbook

Review: Heating curve with heat formulas Scroll down HeatingCurve.htm HeatingCurve.htm

What factors impact change? Intermolecular forces Energy Conditions: T, P, V, amount,

Phase Diagrams: What is added to this diagram? Why?

Phase diagrams 8lcr8&feature=endscreen&NR=1 8lcr8&feature=endscreen&NR=1

T °C 200 °C -2 °C 100 °C -2 °C 30 °C 100 °C P - atm1 atm 100 atm0.001 atm0.8 atm1 atm PhaseLiquidVapor For Water A = B= C= D=

PHET States of Matter es-of-matter es-of-matter

Phase Diagrams. Use the phase diagram for water below to answer the following questions. What is the state of water at 2 atm and 50  C? What phase change will occur if the temperature is lowered from 80  C to -5  C at 1 atm? You have ice at -10  C and 1 atm. What could you do in order cause the ice to sublime? Review: Interpreting Phase Diagrams

Interpreting a Phase Diagram of Water at varying pressures Example: 100 atm

1)What is the normal melting point of this substance? ________ 3)What is the normal boiling point of this substance? ________ 4)What is the normal freezing point of this substance? ________ 5)If I had a quantity of this substance at a pressure of 1.25 atm and a temperature of 0 0 C and heated it until the temperature was C, what phase transition(s) would occur? At what pressure(s) would they occur? 6)At what temperature do the gas and liquid phases become indistinguishable from each other?________ 7)If I had a quantity of this substance at a pressure of 0.25 atm and a temperature of C, what phase change(s) would occur if I increased the pressure to 1.00 atm? At what temperature(s) would they occur?

Water: Connecting Phase Diagram and Heating Curve

Vapor Pressure – Physical Equilibrium The vapor pressure is the pressure measured when there is an equilibrium between the gas and liquid phases. The rates of condensation and vaporization are equal.

Vapor pressure s/vpress.html s/vpress.html Discovery Ed video

Resources for S, L, G HeatingCurve.htm

How does the chemical composition of a substance impact whether it is a gas, liquid or solid at room temperature?

Factors that Impact State of Matter 1. Type of compound – Ionic, Covalent, Metallic 2. Shape 3. Size 4. Polarity Together impacts intermolecular forces

Shapes of Molecules shape-of-a-molecule-george-zaidan-and- charles-morton shape-of-a-molecule-george-zaidan-and- charles-morton PHET simulation (?) ecule-shapes ecule-shapes

Intermolecular Forces Impact state of matter for molecules  Covalent Compounds Forces between molecules  Not between individual atoms Much weaker than the bonds within a molecule (intramolecular bond)  Much weaker than ionic, covalent & metallic bonds

Intermolecular Forces Three Types  Hydrogen  Dipole – dipole  London Dispersion (Van der Waals) Based on weak attraction between molecules  partial negative – partial positive

Polarity ecule-polarity ecule-polarity Use real molecules tab  Molecular dipoles  Electronegativity  Electron density or electrostatic potential Note: VSEPR – valence shell electron pair repulsion impacts shape

Types of Intermolecular Forces Strongest intermolecular force  Hydrogen “ bond” (~ 10% of a covalent bond)  Molecule must be polar (+ and – sides)  H in one molecule is attracted to the N,O,F of another molecule  Hydrogen Bond - bad choice of words – an attractive force, not a bond

Hydrogen “bonds”: attraction between H with N, O, F

Types of Intermolecular Forces Other intermolecular forces  Dipole-dipole – all polar molecules (weaker)  London dispersion forces – all molecules (weakest)

Dipole-dipole Based on polarity of molecules Found with polar covalent compounds Use with elements other than H attracted to N, O or F

London Dispersion Weakest Temporary polarity Based on movement of the electrons around the nucleus Impacts all molecules – non-polar and polar

Why is water unique? Why does ice float on water? float-in-water-george-zaidan-and-charles- morton float-in-water-george-zaidan-and-charles- morton Hydrogen bonds -