Q3_Week 3_LAS 1 - Heating Curve and Cooling Curve Interpretation.pdf
- 1. Name: _____________________________ Grade & Section: ____12_________ Score: _____________ School: ____________________________ Teacher: _______________ Subject: General Chemistry 2 LAS Writer: Jenelyn D. Bongcayao Content Editor: Retchie Joy B. Pisaňa, Eda F. Fale, Christine Joy G. Sua Lesson Topic: Phase Changes and Phase Diagram Interpretation of a Substance. (Quarter 3, Week 3, LAS 1) Learning Targets: Determine and explain the heating and cooling curve of substance. (STEM_GC11IMFIIIa-c- 109) Reference(s): 2004. "Types of Intermolecular Forces." In Chemistry: You and the Natural World, by Teresita F. Religioso Estrella E. Mendoza, 157. Quezon City: Phoenix Publishing House. Interpretation of Heating Curve and Cooling Curve of Substances Phase changes occur when heat is added or removed from a substance. The added energy is used by the substance in either of two ways when a substance is heated: (a) The added heat increases the kinetic energy of the particles and the particles move faster resulting in an increase in temperature; and (b) The added heat is used between particles to break off attractive forces. There is no observed increase in temperature when this happens. A change in the physical appearance (phase change) of the substance is often observed. Conversely, in two ways, the loss or release of heat results in: (a) A decline in the particles' kinetic energy where the motion of the particles slows down & a decrease in temperature is observed; and (b) Forces of attraction are formed, and there may be a phase transition with no change in temperature. Example In figure 1, between points A & B, the material is a solid. The heat supplied to the material is used to increase the kinetic energy of the molecules and the temperature rises. Between B & C, the solid is melting. Heat is still being supplied to the material but the temperature does not change. Heat energy is not being changed into kinetic energy. Instead, the heat is used to change the arrangement of the molecules. At point C, all of the materials have been changed to liquid. Between C & D, the heat supplied is again used to increase kinetic energy of the molecules and the temperature of the liquid starts to rise. Between C & D, the liquid is heated until it starts to boil. Between D & E, the liquid is still being heated but the extra heat energy does not change the temperature (kinetic energy) of the molecules. The heat energy is used to change the arrangement of the molecules to form a gas. At point E, all of the liquid has been changed into gas. Between E & F, the gas is heated and the heat energy increases the kinetic energy of molecules once more, so the temperature of the gas increases. When a system contains only one phase (solid, liquid, or gas), the temperature will increase when it receives energy. The rate of temperature increase is dependent on the heat capacity of the phase in the system. When the heat capacity is large, the temperature increases slowly, because much energy is required to increase its temperature by one degree. Thus, the slopes of temperature increase for the solid, liquid, and gases are different. Activity TRUE or FALSE. For questions 1-3, write T if the statement is correct and F is it is wrong in the space provided. ____ 1. The heating curve is a plot of temperature versus time. ____ 2. The heating and cooling of substances can be determined by the diagonal lines of the curve. ____ 3. HF boils at faster than HCl, thus, HCl has the stronger intermolecular forces. For items 4 – 10, refer to figure 2 and answer the given questions on the space provided. ____ 4. What letter represents the boiling point of the substance? ____ 5. What letter shows the melting point of the substance? ____ 6. Which letter represents the heating of solid? ____ 7. Which letter represents the heating of gas? ____ 8. Which letter represents the melting of solids? ____ 9. Which letter represents the boiling of liquids? ____ 10. No temperature change in point b-d even though heat is added. For items 11 – 15, refer to figure 3 and answer the given questions on the space provided. ____ 11. Water is liquid at 2 atm and 50o C. ____ 12. Melting of substance occurs if temperature is lowered from 80o C to - 5o C at 1 atm. ____ 13. Based on the data, phenol at 99o C is solid. ____ 14. Ammonia at -25o C is gas. ____ 15. Phenol at 25o C is solid. Figure1. Heating Curve (top) and Cooling Curve (bottom) for Water at 1.00 atm pressure. Figure 2. General Heating Curve Figure 3. Phase Diagram