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Energy changes in chemical reactions

Energy changes in chemical reactions. System vs. Surrounding. Thermal energy (a form of kinetic energy from the motion of molecules, that creates heat) Can get transferred from a Chemical system (set of reactants & products in a reaction) To a

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Energy changes in chemical reactions

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  1. Energy changes in chemical reactions

  2. System vs. Surrounding Thermal energy (a form of kinetic energy from the motion of molecules, that creates heat) Can get transferred from a Chemical system (set of reactants & products in a reaction) To a Surrounding (all that is around the chemical reaction) Via two processes known as………

  3. Exothermic & Endothermic Exothermic – heat (measured by temperature) moves from system to surrounding Eg. Heat is released since the surroundings feel warmer Like a bonfire: system = wood pile/flames surrounding = air around fire pit Endothermic – heat moves from surroundingtosystem Eg. Heat is absorbed since the surroundings feel colder Like an ice cube melting in your hand: system = ice cube surrounding = your hand

  4. Graphical Analysis –Exothermic vs. Endothermic

  5. Comparison of Energy in Physical Chemical & Nuclear Reactions

  6. Types of Systems Open system: both matter and energy can enter & leave Closed system: only energy can enter & leave but matter can not Isolated system: ideally neither matter or energy can enter & leave

  7. Calorimetry Process of quantitatively determining the heat changes (q) associated with chemical reactions. A chemical reaction is carried out in a well insulated vessel (called a calorimeter) that represents a closed system. Heat generated from the chemical reaction gets transferred to a liquid inside the calorimeter and temperature changes are recorded.

  8. 1st Law of Thermodynamics States that energy must be conserved in a chemical reaction; heat lost by the system must be gained by the surrounding. Calculate this energy transfer by: q = mcDT Where q is heat transferred in kJ m is mass of substance gaining/losing heat in kg c is heat capacity of substance gaining/losing heat in kJ/kgC DT is temperature change in C *Heat capacity is a unique calculated value for each substance that represents the amount of energy needed to raise the temperature of 1g of a substance 1C Water = 4.18 kJ/kgC Small values heat up quickly and cool down quickly

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