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Thermochemistry

Thermochemistry. After reading Section 11.1, you should know:. The relationship between energy and heat The difference between heat capacity and specific heat How to determine whether a reaction is endothermic or exothermic . Energy Transformations. Thermochemistry

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Thermochemistry

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  1. Thermochemistry

  2. After reading Section 11.1, you should know: • The relationship between energy and heat • The difference between heat capacity and specific heat • How to determine whether a reaction is endothermic or exothermic

  3. Energy Transformations • Thermochemistry • the study of heat changes that occur during chemical reactions • Energy • The capacity to do work or produce heat

  4. Types of Energy • Chemical potential energy – energy stored within the structural units of chemical substances. • Kinetic energy – energy an object has because of its motion

  5. Heat vs. Temperature • Heat (q) – a form of energy • flows from a warmer region to a cooler one. • Temperature – a measure of the average kinetic energy of the atoms or molecules in a substance.

  6. In any chemical or physical process, energy is neither created nor destroyed. Law of Conservation of Energy

  7. System vs. Surroundings • system – the part of the universe upon which attention is focused • surroundings – the remainder of the universe that is outside the system

  8. Endothermic vs. Exothermic • endothermic – heat flows into the system; heat is absorbed from the surroundings; surroundings become cold; ∆H > 0 (heat change is positive) • exothermic– heat flows out of the system; heat is released from the system to the surroundings; surroundings become hot; ∆H < 0 (heat change is negative)

  9. Endothermic vs Exothermic • Endothermic • P.E. (products)>P.E. (reactants) • ∆H>0 (positive) • Heat absorbed • Surroundings cold • Heat is a reactant • Energy to break bonds > energy to make bonds • Exothermic • P.E. (products)<P.E. (reactants) • ∆H<0 (negative) • Heat released • Surroundings hot • Heat is a product • Energy to break bonds < energy to make bonds

  10. Heat Capacity • Heat Capacity – amount of heat needed to increase the temperature of an object by 1C. • The greater the mass of the object, the greater the heat capacity.

  11. Specific Heat (Cp) – amount of heat needed to increase the temperature of a substance by 1C. Cp = heat/(mass * ΔTemp) units (J/goC) Water has a high specific heat compared to other substances Specific Heat

  12. After reading Section 11.1, you should know: • The relationship between energy and heat • The difference between heat capacity and specific heat • How to determine whether a reaction is endothermic or exothermic

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