# Kinetic Energy Is the Energy of Motion: KE= Mv2

Tags THERMOCHEMISTRY

• Kinetic energy is the energy of motion: KE= ½ mv2
• Potential energy is the energy an object possesses by virtue of its location. Potential energy can be converted to kinetic energy.
• SI unit is the Joule: 1J= 1kgxm2/s2
• 1 calorie= 4.184 joules
• A system is the part of the universe we are studying. The surroundings are everything else.
• Force is a push or pull on an object.
• Work is the amount of force applied to an object over a distance: w=Fxd
• Heat is the energy transferred from a hotter object to a cooler object.
• Energy is the capacity to do work or transfer heat.
• The first law of thermodynamics states that energy can not be created or destroyed. The total energy of(system+surroundings) is constant.
• The total energy of a system(KE+PE) is called the internal energy.
• E=Efinal – Einitial

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• When a system undergoes a physical or chemical change, the change in internal energy is equal to the heat added to or liberated from the system plus the work done on or by the system: E= q+w
• When heat is transferred from the surroundings to the system q0 ( system is cold to the touch because it is absorbing heat from your hand)
• Work done by the surroundings on the system is positive,w0.
• Endothermic reactions absorb heat from the surroundings. Exothermic reactions liberate heat to the surroundings.
• A state function depends on only the initial and final states of the system. E is a state function. q and w are not.
• A state function does not depend on how the internal energy is used.
• Enthalpy is the heat transferred between a system and the surroundings during a chemical reaction carried out under constant pressure: H
• H= Hfinal-Hinitial = qp
• Endothermic reactions have a positive enthalpy, exothermic reactions have a negative enthalpy.
• Enthalpy of reaction: H= Hproducts- Hreactants
• 2H2 + O22H2O H = -483.6 kJ What does this thermochemical equation tell you?
• Enthalpy is an extensive property. The magnitude is dependent on the amount of reactant. Burning 1 mole of methane produces 890 kJ. Burning 2 moles produces 1780 kJ.
• The sign of H depends on the direction of the reaction. The reverse reaction is equal in magnitude but opposite in sign.
• Calorimetry is the measure of heat flow.
• Heat capacity is the amount of energy required to raise the temperature of an object 1 degree C. Molar heat capacity is the heat capacity of 1 mole of substance. Specific heat is the amount of energy required to raise the temperature of 1 gram of substance 1 degree C.
• q=(specific heat) x (grams of substance) x T
• H= qp
• qsol= ( specific heat of solution)x (grams of solution) x T= -qrxn
• Constant volume calorimetry is carried out in a bomb calorimeter. Typically used for combustion reactions.
• qrxn= - Ccal x T
• Hess’s Law: If a reaction is carried out in steps, H for the reaction is the sum of the H’s for each of the steps.
• Example:CH4(g)+2O2(g)CO2(g)+2H2O(g) H= -802 kJ

2H2o(g) 2H2O(l) H=-88 kJ

CH4(g)+2O2(g)CO2(g)+2H2O(l)H=-890kJ

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