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In this lesson we will study the condensed phases of matter - the solid and the liquid phases. In the gas phase the attraction between particles of gas is negligible - in fact, we assumed that it was zero. But in the condensed phases, those attractive forces are important, they bind the molecules (or atoms) together in the liquid and solid phases. Therefore, one of the things we will look at is the nature - and especially the relative strength - of the intermolecular bonds in solids and liquids and try to relate their strength to some of the common properties: melting point, boiling point, surface tension, vapor pressure, and so on. We will also learn to calculate the amount of energy that is needed to heat (or that is released on cooling) a solid or a liquid as well as the amount of energy involved in changing from a solid to a liquid and from a liquid to a gas. As you might suspect, the amount energy involved also depends on how strongly the particles are bound together as well as on how much of the material is involved. The lab exercise for this lesson involves measuring the amount of heat required to change the temperature of a sample of a metal. Be sure to review the objectives for this lesson (below) as you are working through it. There is also a lab exercise and a problem set to turn in. Additional reading and practice problems from the text are listed below the objectives. When you have completed the lesson, take the Self Quiz in your workbook and check your answers by going to the Wrap Up page. You can take the quiz for this lesson when you come to lab next week to do the lab work for Lesson 3.
OBJECTIVES You have completed this lesson when you can: 1. Describe the bonding and molecular motion in the solid, liquid, and gas phases. 2. Describe the types of interatomic bonds (covalent, ionic, metallic) and intermolecular bonds (hydrogen, dipole-dipole, van der Waals) and compare their strengths to one another. (Review) 3. From formulas of chemicals, determine what types of interatomic and intermolecular bonds the chemicals have. (Review) 4. Describe energy, heat, and temperature. 5. Describe the relationship between heat and temperature. 6. Define and properly use the terms endothermic and exothermic. 7. Relate chemical bonds to the energy changes involved in making and breaking them. 8. Draw and interpret heating and cooling curves. 9. Define calorie, kilocalorie (and Calorie), and joule. 10. Define heat capacity (or specific heat) and memorize the value of the heat capacity (or specific heat) for water. 11. For a material changing temperature, do calculations relating the heat lost or gained, change in temperature, mass of the material, and heat capacity (or specific heat) of the material. 12. Define and use proper symbols, units, and signs for heat of fusion, heat of vaporization, heat of condensation, and heat of crystallization. 13. For a material changing phase, do calculations relating the heat lost or gained, mass of the material, and DH for the phase change. 14. For materials changing temperature and phase, do calculations relating the heat lost or gained, change in temperature, heat capacity (specific heat), mass of the material, and DH for the phase change. 15. Interpret heating and cooling curves in terms of bonding. 16. Relate chemical bonds (interatomic and intermolecular) to the processes involved in making and breaking them. 17. Use kinetic molecular theory and bonding to describe phases, phase changes, melting and boiling points, and heating and cooling curves. 18. Identify and describe viscosity, surface tension, volatility, pressure, and vapor pressure. 19. Relate thermal properties of different chemicals to differences in interatomic and intermolecular bonds.
ASSIGNMENTS: Reading in text: Find the chapters and sections in your text that cover the following topics and read them. Solids HPBA-6: Chapter 13 Practice problems in text- HBPA-6: Chapter 13 exercises 26, 27, 30, 35, 63-68, 92-95 To be turned in: Lab Report on Exercise 18 (or Exercise 19, if you prefer)
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