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DO NOW: Energy Transformations

DO NOW: Energy Transformations. Match the different types of energy transformation in each picture. IRON WINDMILL MIXER SUN a. b. c. d. 1. Electrical to Mechanical ___________

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DO NOW: Energy Transformations

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  1. DO NOW: Energy Transformations Match the different types of energy transformation in each picture. IRON WINDMILL MIXER SUN a. b. c. d. 1. Electrical to Mechanical ___________ 2. Nuclear to Thermal ___________ 3. Mechanical to Electrical ___________ 4. Electrical to Thermal ___________

  2. Temperature and Heat

  3. What is temperature? Temperatureis the measure of the average kinetic energy of the particles of matter. You need a thermometer to measure temperature.

  4. Temperature Scales There are three types of temperature scales: • Fahrenheit(F) • Celsius(C) • Kelvin(K).

  5. Although the Fahrenheit scale is widely used, the Celsius scale is more compatible with temperature measurements used in the metric system. Even though the Fahrenheit and Celsius temperature scales are extremely useful for various applications, the Kelvin scale is used to measure temperature in the International System of Units (SI).

  6. What is absolute zero? The difference between the Kelvin and Celsius scales is the location of the zero point. The zero point of the Kelvin scale (0K), called absolute zero, corresponds to -273C. Absolute zero is the point at which the motion of particles of matter ceases.

  7. Temperature Conversions Conversions between these two scales can be made by using the following formulas: C + 273 = K K – 273 = C.

  8. What is heat? Heat is defined as the transfer of kinetic energy from a hotter object to a colder object. Heat is measured in units of joules or calories.

  9. Example • A hot drink left in a cold place will always lose heat to the surroundings. It will get cooler until eventually it is at the same temperature as its surroundings. But if it is inside a good thermal insulator (such as a thermos flask), it will lose the heat very slowly.

  10. Exothermic Reactions Reactions that release heat to its surroundings are called exothermic reactions. When an exothermic reaction releases heat to its surroundings, the temperature of the surroundings increases.

  11. Endothermic Reactions Reactions that absorb heat are called endothermic reactions. When an endothermic reaction absorbs heat, the temperature of its surroundings decreases.

  12. What is heat capacity? The size of the temperature increase depends on how much heat is released and on the heat capacity of the surroundings. The heat capacityof an object is the amount of heat needed to raise the temperature of the object by 1 Celsius degree. The heat capacity of an object depends on its mass and its composition. A large mass of water can absorb a large quantity of heat with only a small temperature increase.

  13. What is specific heat? The heat capacity of 1 gram of a substance is called its specific heat. The specific heat is a physical property of the substance like its color and melting point. Different substances have different capacities for storing energies.

  14. SPECIFIC HEAT OF SOME SUBSTANCES SubstanceSpecific Heat (J/g C) H2O (l) 4.184 H2O (s) 2.03 Al (s) 0.89 C (s) 0.71 Fe (s) 0.45 Hg (s) 0.14

  15. Heat Calculations The amount of heat given off or absorbed can be calculated by the following formula: (Tf - Ti) Q = m x T x Csp Q = heat (measured in Joules (J) or calories (cal)) m = mass (g) T = change in temperature (T = final temperature (Tf) – initial temperature (Ti)) Csp= specific heat (J/gC or cal/gC)

  16. SAMPLE PROBLEMS: • If the specific heat of water is 4.184 J/gC, how much heat must be added to 5 g of aluminum to raise its temperature by 2 Celsius degrees? Q = m x T x Csp Q = m = T = Csp=

  17. 2. The specific heat of aluminum is 0.89 J/g C. How much heat is required to raise the temperature if 16 grams of aluminum from 25C to 75C? Q = m x T x Csp Q = m = T = Csp=

  18. A sample of KCl dissolves in 75g of H2O. The temperature changes from 21.6°C to 31°C. How much heat was exchanged? (Csp of water = 4.184 J/g°C or 1 cal/g°C) Q = m =  T = Csp=

  19. What is the specific heat of aluminum if the temperature of a 28.4g sample of aluminum is increased by 8.1C when 207 J of heat is added? Q = m x T x Csp Q = m = T = Csp=

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