Unit 1 Phase Changes

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  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • (Heat always flows spontaneously from the hot source to the cold source.)
  • After completing the previous experiments, it should be evident that the heat "lost" from the candle is equal to the "heat" gained by the water, or that a constant fraction of the energy transferred goes to warm the water.
  • After completing the previous experiments, it should be evident that the heat "lost" from the candle is equal to the "heat" gained by the water, or that a constant fraction of the energy transferred goes to warm the water.
  • (Heat always flows spontaneously from the hot source to the cold source.)
  • the quantity of heat absorbed or lost is directly proportional to the mass. b. the quantity of heat absorbed or lost is directly proportional to change in temperature. c. the mass and change in temperature are inversely proportional. d. for every different substance there is a constant specific heat that does not vary.
  • After completing the previous experiments, it should be evident that the heat "lost" from the candle is equal to the "heat" gained by the water, or that a constant fraction of the energy transferred goes to warm the water.
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • Ethylene Glycol is an organic liquid called anti-freeze which is added to water to make an aqueous solution of Ethylene Glycol and water. This is to prevent water in the radiator of the vehicle from boiling over. It elevates the boiling point of water. At the same time, anti-freeze will depress the freezing point of that same water to prevent freeze up in the winter, hence the name of the solution, "anti-freeze". This ability for a solute to elevate the boiling point and depress the freezing point of the solvent is the focus of this page
  • A pure substance is matter in which the particles that make it up are all of the same kind. A mixture contains more than one kind of particle. In mixtures, the individual components of the mixture retain their properties. For example, water is a pure substance if it only contains water molecules, but tap water is a mixture because it contains added chlorine, fluorine, dissolved air and sometimes other things like bacteria and metals we are not happy about. Pure substances can be in the form of elements or compounds. Elements are called the building blocks of matter, since they contain only on type of atom. Compounds are pure substances that contain two or more different atoms joined chemically. We call this chemical joining a chemical bond. Mixtures can be heterogeneous and homogeneous. The particles in a heterogeneous mixture are not evenly distributed and individual particles are often distinguishable. For example, a mixture of sand and water or salt and pepper are heterogeneous. The individual particles of a homogeneous mixture are evenly distributed and cannot be easily separated. For example, when solid sugar is dissolved in water, only a liquid is observed and the solid sugar particles are not visible.
  • Unit 1 Phase Changes

    1. 1. Chemistry 30S Unit 1 Physical Properties of Matter
    2. 2. <ul><li>A phase change is a change in the state of matter without any change in the chemical composition of the system. A phase change involves energy change but never involves temperature changes. </li></ul>Phase Changes C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    3. 3. C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    4. 4. Energy Increased and Absorbed by Substance: SOLID to LIQUID Melting LIQUID to GAS Vaporization SOLID to GAS Sublimation GAS to PLASMA Ionization In all of these phase changes ENERGY IS ABSORBED . The initial state has a lower internal energy than the new state, so absorbs energy to change state. (A cooling process ) C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    5. 5. Energy Decreased and Released by Substance: GAS to SOLID Deposition GAS to LIQUID Condensation   LIQUID to SOLID Solidification PLASMA to GAS Deionization In all of these phase changes ENERGY IS RELEASED . The initial state has a greater internal energy than the new state, so releases energy to change state. (A warming process) C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    6. 7. <ul><li>Endothermic (Energy put in) Melting, Boiling, Ionization, Sublimation </li></ul><ul><li>Exothermic (Energy released) Freezing, Condensation, Deionization, Deposition </li></ul>
    7. 8. Heating / Cooling Curves When a substance is heated, it undergoes several phase changes. A heating curve is a diagram that illustrates the phase changes that occur when a substance is heated. A cooling curve is a diagram that illustrates the phase changes that occur when a substance is cooled. C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    8. 9. Heating / Cooling Curves C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    9. 10. Heating / Cooling Curves Note that the melting and boiling processes require the addition of a specific amount of energy to break the forces holding the water molecules together. The temperature does not rise during the time of phase change because the energy is being used to change the phase of the material. When a liquid solidifies or condenses, the opposite occurs: energy is released and once again the temperature will remain constant. C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    10. 11. Solid F.P. / M.P. Liquid B.P. / C.P. Gas
    11. 12. <ul><li>Freezing , solidification or crystallization is known as the change in state from solid to liquid. The freezing point of a substance is the temperature at which a substance freezes. </li></ul><ul><li>As a substance freezes (energy is lost), the particles begin to slow down and the forces of attraction between the particles, or intermolecular forces begin to increase and take hold. As the intermolecular forces increase, the particles arrange themselves into an organized repeating pattern called a crystal. </li></ul>Phase Changes – Freezing & Melting C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    12. 13. <ul><li>Melting or fusion is the change in state from solid to liquid. The melting point of a substance is the temperature at which a substance melts or fuses. </li></ul><ul><li>As a solid is heated (energy is absorbed), the forces of attraction between the particles of the crystal are slowly overcome, allowing some particles to move more freely. As more particles are free from the crystal, the substance melts. </li></ul>Phase Changes – Freezing & Melting C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    13. 14. <ul><li>Vaporization is the process by which a liquid changes to a gas or vapour. </li></ul><ul><li>A vapour is the gaseous state of a substance that is normally liquid or solid at room temperature. </li></ul><ul><li>When vaporization only occurs at the surface of a liquid, the process is called evaporation . </li></ul><ul><li>Substances that evaporate rapidly are said to be volatile. </li></ul>Phase Changes - Vaporization C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    14. 15. <ul><li>If a sample of liquid is left open to the air, particles at the surface may collide with other particles and absorb enough kinetic energy to overcome the forces of attraction and change into the gaseous state. However, if that particle collides with an air particle above it, it may lose energy and become part of the liquid again (condense). </li></ul>Phase Changes C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    15. 16. <ul><li>More particles and therefore generally greater forces of attraction surround a particle within the liquid as in the diagram. If a particle within the liquid absorbs enough energy to change into a gaseous particle it is more likely to collide with another liquid particle, lose energy and return to the liquid state. This argument can be used to explain why </li></ul><ul><li>evaporation is a surface </li></ul><ul><li>phenomenon. </li></ul>Phase Changes C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    16. 17. <ul><li>Simple experiments show that if the surface area is increased, the rate of evaporation increases. At the surface, there are 2 processes occurring: a rate of evaporation and a rate of condensation as gaseous particle are ‘recaptured’ by the liquid state. If a container of liquid is open, the rate of evaporation will usually exceed the rate of condensation and the level of the liquid will drop as liquid particles move into the gaseous state. </li></ul>Phase Changes C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    17. 18. <ul><li>If a container of liquid is open, the rate of evaporation will usually exceed the rate of condensation and the level of the liquid will drop as liquid particles move into the gaseous state. Physical Properties of Matter However, if the container is closed, the rate of condensation will eventually equal the rate of evaporation and the level of the liquid will no longer change, if the temperature is kept constant. This is called a dynamic equilibrium . </li></ul>Phase Changes C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    18. 19. Phase Changes - Animations C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    19. 20. Phase Changes - Animations C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    20. 21. Phase Changes - Animations C30S-1-04 Explain the process of melting, solidification, and deposition in C30S-1-05 terms of the KMT. Include: freezing point Use the KMT to explain evaporation and condensation
    21. 22. Vapour Pressure Design an Experiment C30S-1-06 Operationally define vapour pressure in terms of observable and measurable properties.
    22. 23. <ul><li>Can water boil at 90 o C? If so, why does it? </li></ul><ul><li>How would cooking high up on a mountain differ from sea level? </li></ul><ul><li>How does a pressure cooker work? </li></ul>Discrepant Event C30S-1-06 Operationally define vapour pressure in terms of observable and measurable properties.
    23. 24. <ul><li>One of the physical properties that we can measure for liquids and solids is vapor pressure . All solids and liquids, that is, all substances in condensed phases, exhibit a vapor pressure. This is a pressure of the substance in the gas phase which is established at a particular temperature. The vapor pressure of a substance depends upon the temperature. The pressure of a vapor in equilibrium with its liquid state is called equilibrium vapor pressure or simply vapor pressure . </li></ul>Vapour Pressure C30S-1-06 Operationally define vapour pressure in terms of observable and measurable properties.
    24. 25. Vapour Pressure C30S-1-06 Operationally define vapour pressure in terms of observable and measurable properties.
    25. 26. <ul><li>The Vapor Pressure of a liquid at a given temperature is a characteristic property of that liquid. As the temperature increases, the liquid ’ s vapor pressure increases. At some temperature, the vapor pressure is great enough to form a bubble inside the liquid. As these bubble begin to form below the surface of the liquid, boiling has begun. </li></ul>Vapour Pressure & Boiling Phase Change animation C30S-1-06 Operationally define vapour pressure in terms of observable and C30S-1-07 measurable properties and operationally define normal boiling point in terms of vapour pressure.
    26. 27. <ul><li>T he boiling point of a liquid is that temperature at which vapor pressure equals atmospheric pressure. </li></ul><ul><li>The normal boiling point is described as the temperature at which boiling occurs when the external pressure is standard pressure (101.3 kPa, 1 atmosphere, or 760 mmHg). </li></ul>Vapour Pressure C30S-1-06 Operationally define vapour pressure in terms of observable and measurable properties.
    27. 28. Vapour Pressure Why do the 3 curves all look so different? C30S-1-06 Operationally define vapour pressure in terms of observable and C30S-1-07 measurable properties and operationally define normal boiling point in terms of vapour pressure.
    28. 29. <ul><li>Vapor pressure will indicate the strength of the attractive forces within a liquid. The higher the vapor pressure, the lower the strength of the attractive forces. </li></ul><ul><li>Vapor pressure will determine the rate of evaporation for a liquid. The higher the vapor pressure, the faster the rate of evaporation. </li></ul><ul><li>Vapor pressure will have a direct impact on boiling. The higher the vapor pressure of a liquid, the less the liquid must be heated to match the atmospheric pressure. Therefore, high vapor pressures are associated with substances having low boiling points. </li></ul>Vapour Pressure - Summary C30S-1-06 Operationally define vapour pressure in terms of observable and C30S-1-07 measurable properties and operationally define normal boiling point in terms of vapour pressure.
    29. 30. Determining The Normal Boiling Point of Various Substances C30S-1-07 Operationally define normal boiling point in terms of vapour pressure.
    30. 31. Determining The Normal Boiling Point of Various Substances C30S-1-07 Operationally define normal boiling point in terms of vapour pressure.
    31. 32. <ul><li>What affect would adding a solute have on the boiling point? </li></ul>Boiling Point & Adding A Solute
    32. 33. Boiling Point Elevation When a solute is added to a solvent, the vapor pressure of the solvent (above the resulting solution) is less than the vapor pressure above the pure solvent. The boiling point of a solution, then, will be greater than the boiling point of the pure solvent because the solution (which has a lower vapor pressure) will need to be heated to a higher temperature in order for the vapor pressure to become equal to the external pressure (i.e., the boiling point). In other words from a molecular view we might expect the boiling point to be elevated when solute is increased in a solution.
    33. 34. Heat Effects in Changes of State Heat versus Temperature Heat is the measure of the quantity of energy in a system. Temperature is the measure of the intensity of that energy in the system &quot;Given a bathtub full of water and a sink full of water, both having a temperature of 30°C, which will melt more ice cubes?&quot;
    34. 35. Heat Effects in Changes of State Both have the same intensity of energy, or in other words, the same amount of thermal energy concentrated in each cm 3 of water. The water in the bathtub and sink, therefore, must have the same temperature. It is obvious, however, that more ice cubes would melt in the bathtub than the sink because the water in the bathtub contains a lot more energy or heat than the water in the sink.
    35. 36. Heat Effects in Changes of State Different instruments are needed to measure temperature and heat. A thermometer is used to measure temperature. A calorimeter is used to measure heat.
    36. 37. Heat can only be measured when energy is being transferred from one object to another. Temperature is measured by simply placing a thermometer in a substance and reading the intensity or concentration of the thermal energy in that substance. A calorimeter is used to measure the heat being transferred from one object having more energy (hot source) to an object having less energy (cold source).
    37. 38. Law of Heat Gain Temperature and heat are different, and are measured in different units. Temperature is measured in degrees Celsius (°C). Heat, like other energy forms, is measured in the S.I.. unit joule (J). An older unit of energy is the calorie. Dieticians still use the food Calorie (equal to 1000 calories).
    38. 39. Law of Heat Gain The relation between joules and calories is 1 cal = 4.184 J. 3 mini experiments
    39. 40. Measuring the Temperature of a Mixture of Hot and Cold Water
    40. 41. Law of Conservation of Heat The Law of Conservation of Energy states that in all reactions, energy is neither created nor destroyed. Analyzed in terms of the hot and cold water from the previous example, this means that the energy lost by the hot water was gained by the cold water. In other words, no energy was lost, it was simply transferred from one substance to another.
    41. 42. Predict the Final Temperature When Hot and Cold Water are Mixed <ul><li>Predict the final temperature when: </li></ul><ul><ul><li>60 g of water at room temperature (22°C) are mixed with 60 g of water at 50°C </li></ul></ul><ul><ul><li>30 g of water at room temperature (22°C) are mixed with 60 g of water at 50°C </li></ul></ul><ul><ul><li>30 g of water at 50°C are mixed with 60 g of room temperature [33.2°C] water </li></ul></ul><ul><ul><li>40 g of water at 50°C are mixed with 60 g of room temperature (22°C) water </li></ul></ul>
    42. 43. What do you observe in the picture? Why do firefighters wear protective clothing?
    43. 44. Heat Capacity/Specific Heat Each material is able to &quot;hold&quot; a certain amount of thermal energy at a given temperature, due to what we call its specific heat . We have seen that the mass, the change in temperature, and the heat capacity (or specific heat) are all important in determining the quantity of heat lost or gained by a substance.
    44. 45. <ul><li>The specific heat of any substance is the amount of heat required to raise one gram of that substance one degree Celsius. </li></ul><ul><li>Some objects require more heat than others to raise their temperature. </li></ul>Heat Capacity/Specific Heat
    45. 46. The heat required to raise one gram of a substance by one degree Celsius is called ____. A. joule B. calorie C. specific heat D. energy
    46. 47. Heat Capacity/Specific Heat Mathematically they can be combined into q = m·  T·C p q is the amount of heat lost or gained m is the mass C is the specific heat  T is the change in temperature. Do Questions 4-6 on page 521 in your textbook. .
    47. 48. Calorimetry <ul><li>A calorimeter is an insulated device used for measuring the amount of heat absorbed or released in a chemical reaction or physical process. </li></ul>
    48. 49. Calorimetry
    49. 50. Measuring the Heat Capacity of a Metal Your assignment is to design an experiment and determine the heat capacity of a designated metal. You will be given an unknown metal and you must design an experiment to determine its heat capacity. Once the heat capacity is calculated, you will compare it against known values for certain metals to ascertain what metal it is.
    50. 51. Format for a LAB REPORT
    51. 52. Heat Capacity/Specific Heat Do Questions 12-15 on page 525 in your textbook.
    52. 53. Latent Heat When a substance changes phase, heat can be transferred in or out without any change in temperature. This occurs because of the energy required to change phase. What is happening is that the internal energy of the substance is changing, because the relationship between neighboring atoms and molecules changes.
    53. 54. Latent Heat The change in internal energy associated with a change in phase is known as the latent heat . It is called latent heat because there is no temperature change associated with this energy transfer, there is only a change in phase.
    54. 55. Latent Heat of Fusion & Vaporization For a liquid-solid phase change, it's called the latent heat of fusion . For a liquid-gas phase change, it's called the latent heat of vaporization .
    55. 56. Latent Heat Page 346 Q. 4 - 7
    56. 57. Lab Competition MEASURING THE HEAT OF FUSION OF ICE
    57. 58. ASSESSMENT C30S-1-03 Explain the properties of liquids and solids using the KMT.

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