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Agenda:

Agenda: . Homework:. Thermochemistry Heating & Cooling Curves – a review Graphing temperature change Phase Change Diagrams Why are some compounds liquids and gases at room temperatures ?. Characteristics of Solids, Liquids & Gases. Sort the terms into 3 columns: S, L, G

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Agenda:

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

  2. 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

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

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

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

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

  7. 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 = -209.9 °C (-345.81998 °F) M.P. of Silver = 961.93 °C (1763.474 °F) M.P. of Carbon = 3500.0 °C (6332.0 °F)

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

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

  10. 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.

  11. 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 = -195.79 °C (-320.42 °F) B.P. of Silver = 2162 °C (3924 °F) B.P. of Carbon = 4027 °C (7281 °F)

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

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

  14. Energy requirements for water Three formulas : specific heat Q = mCp∆T heat of fusion Q= mHf heat of vaporization Q= mHv Heating Cooling Energy (heat) added Energy (heat) released:

  15. Energy calculations related heating or cooling specific substances Specific heat (Cp) Latent heat Heat of fusion (Hf) Heat of vaporization (Hv) Use reference tables – values for each pure substance

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

  17. 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= mHf • Specific for each pure substance • Use reference tables

  18. 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= mHv • Specific for each pure substance • Use reference tables

  19. 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

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

  21. 4. How many joules does it take to melt 35 g of ice at 0oC? 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 oC to 60 oC? 7. How much heat is given off when 50 g of water at 0oC freezes?

  22. 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

  23. Review: Heating curve with heat formulas Scroll down http://www.kentchemistry.com/links/Matter/HeatingCurve.htm

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

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

  26. Phase diagrams http://www.youtube.com/watch?v=fLOPaJ8lcr8&feature=endscreen&NR=1

  27. For Water A = B= C= D=

  28. PHET States of Matter http://phet.colorado.edu/en/simulation/states-of-matter

  29. Phase Diagrams. Use the phase diagram for water below to answer the following questions. Review: Interpreting Phase Diagrams 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?

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

  31. 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 00 C and heated it until the temperature was 7500 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 -1000 C, what phase change(s) would occur if I increased the pressure to 1.00 atm? At what temperature(s) would they occur?

  32. Water: Connecting Phase Diagram and Heating Curve

  33. Vapor Pressure – Physical Equilibrium

  34. Vapor pressure http://www.chem.purdue.edu/gchelp/liquids/vpress.html Discovery Ed video

  35. Resources for S, L, G http://www.kentchemistry.com/links/Matter/HeatingCurve.htm

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

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

  38. Shapes of Molecules https://ed.ted.com/lessons/what-is-the-shape-of-a-molecule-george-zaidan-and-charles-morton PHET simulation (?) http://phet.colorado.edu/en/simulation/molecule-shapes

  39. 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

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

  41. Polarity • http://phet.colorado.edu/en/simulation/molecule-polarity • Use real molecules tab • Molecular dipoles • Electronegativity • Electron density or electrostatic potential • Note: VSEPR – valence shell electron pair repulsion impacts shape

  42. 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 attractiveforce , not a bond

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

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

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

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

  47. Why is water unique? Why does ice float on water? https://ed.ted.com/lessons/why-does-ice-float-in-water-george-zaidan-and-charles-morton Hydrogen bonds -

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