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The Flow of Energy – Heat

The Flow of Energy – Heat. Chapter 17.1. Warm Up. What happens to the heat from the lava?. Why does lava cool more quickly in water than on land?. Introduction to Thermochemistry.

candace-myers
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The Flow of Energy – Heat

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  1. The Flow of Energy – Heat Chapter 17.1

  2. Warm Up What happens to the heat from the lava? Why does lava cool more quickly in water than on land?

  3. Introduction to Thermochemistry • Thermochemistry (or Thermodynamics) is the study of heat, energy, and temperature changes that occur during chemical reactions (One of the main courses of study in Physical Chemistry) • Law of Conservation of Energy (1st Law of Thermodynamics) – The law of conservation of energy states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant. (Whether a reaction flask or the universe

  4. Temperature vs. Heat • Temperature is the measure of the average kinetic energy of the particles in a substance • Measure using a thermometer • Rises when heat is added • Falls when heat is removed • Heat(q) is the energy that is transferred between two objects • Cannot be measured directly • Can only detect the changes caused by heat HOT COLD

  5. Thermochemical Reactions • System – reactants and products • Surroundings – the reaction container

  6. Exothermic vs. Endothermic Exothermic Endothermic Heat Heat

  7. Measuring Heat • The Joule (J) is the SI unit of heat and energy • The calorie (cal) is also used to measure heat capacity and is defined by the amount of heat needed to raise the temperature of 1g of pure water by 1C • 1 J = 0.2390 cal 1 cal = 4.184 J • NOTE: The energy contained in food is measured in Calories (Cal) = 1000 calories = 1 kcal

  8. Heat Capacity vs Specific Heat • Heat capacity is the amount of heat needed to raise the temperature of a substance by 1C J/C or J/K • Specific heat capacity (C) is the amount of heat needed to raise the temperature of one gram of a substance by 1C J/gC or J/gK

  9. Examples of specific heat capacities

  10. Cool Down Which of these pictures contains more heat? C = q / m xDT q = C x m xDT

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