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Exploring Thermodynamics: Heat Capacity and Calorimetry

Understand thermodynamics by learning about heat capacity, heat change, specific heat, calorimetry, and thermochemical equations. Explore how to calculate heat and energy in various substances. Discover the principles of thermodynamics through practical examples and applications.

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Exploring Thermodynamics: Heat Capacity and Calorimetry

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  1. THERMOCHEMISTRY Chapter 11

  2. The amount of energy needed to to increase the temperature of an object exactly 10C is the heat capacity of that object. (J/0C) The specific heat capacity or simply specific heat of a substance is the amount of heat/ energy needed to raise the temperature of 1g of the substance 10C. (J/g0C) HEAT CAPACITY AND SPECIFIC HEAT

  3. Calculating Heat Capacity • The heat capacity of an object is equal to its specific heat times its mass. • EX. The heat capacity of a 5 gram piece of pure aluminum is equal to: 5g X 0.90J/g0C = 4.50 J/0C

  4. Calculating Specific Heat • C = __q___ = m X ΔT = heat(joules or calories) mass(g) X change in temperature (0C)

  5. Sample Problem • How much heat is required to raise the temperature of 250 g of mercury 52 0C? The specific heat for mercury is: 0.14 J/g0C

  6. SOLVE for q(heat) • C = __q___ m X ΔT • Rearrange the specific heat formula to solve for q. • q = C x m x ΔT NOW PLUG AND CHUG…

  7. ANSWER • q = C x m x ΔT • q = 0.14 J x 250g x 520C = g 0C = 1,800 J or 1.8kJ

  8. CALORIMETRY • Calorimetry is the accurate and precise measurement of heat change for chemical and physical processes. • In calorimetry, the heat released by the system is equal to to the heat absorbed by its surroundings. • What law describes this relationship?

  9. Calorimeter • To measure heat changes accurately and precisely, the process must be carried out in an insulated container. • The insulated device used to measure the absorption or release of heat in chemical or physical processes is called a calorimeter.

  10. Heat of Reaction • A heat of reaction is the heat change for the equation exactly as it is written. • For systems at constant pressure, the heat content is the same as a property called the Enthalpy (H) of the system. (q = ΔH)

  11. Thermochemical Equations • You can treat heat change in a chemical reaction like any other reactant product in a chemical equation. • A chemical equation that includes the heat change is referred to as a thermochemical equation.

  12. ΔH is Positive

  13. ΔH is Negative

  14. Types of Thermochemical Equations Endothermic (ΔH is positive): Na2CO2 + H2O + CO2 + 129kJ NaHCO3 Exothermic (ΔH is negative): CaO + H2O Ca(OH)2 + 65.2KJ

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