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Energy

Energy. HEAT AND TEMPERATURE. Definitions. Heat – the energy transferred between objects that are at different temperatures Temperature – a measure of how hot or cold something is; a measure of the average kinetic energy of the particles in an object. Enthalpy. The total energy of a system

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Energy

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  1. Energy HEAT AND TEMPERATURE

  2. Definitions • Heat – the energy transferred between objects that are at different temperatures • Temperature – a measure of how hot or cold something is; a measure of the average kinetic energy of the particles in an object

  3. Enthalpy • The total energy of a system • Represented by the symbol “H” • If pressure remains constant, the enthalpy increase of a sample of matter is equal to the energy as heat that is received. • This relationship is true when a chemical reaction or a change of state occurs. • Enthalpy includes the kinetic energy of the particles

  4. Temperature Relationships • T°C = T°K – 273 • T°K = T°C + 273 • Absolute 0 – the temperature on the Kelvin scale at which the minimum average kinetic energies of all particles occur(0.00 K)

  5. Molar Heat Capacity • Involves pure substances • Energy (as heat) that is needed to increase 1 mol of the substance by 1 K. • Represented by the symbol “C” • Units are J/K∙mol

  6. Heat vs. Molar Heat Capacity q = nCΔT • q = heat • n = # moles • C = molar heat capacity • ΔT = change in temperature • Remember that the units for C are J/K∙mol so temp. MUST be in K

  7. More on Molar Heat Capacity • Molar heat capacities of all metals are similar – see table on p. 343 • Molar heat capacity is related to specific heat (the energy as heat that is required to raise the temp. of 1 g of a substance by 1 K) • Molar heat is related to moles, specific heat is related to grams

  8. Molar mass and Specific Heat M x Cp = C • M = molar mass (g/mol) • Cp = specific heat (J/K∙g) • C = molar heat capacity (J/K∙mol)

  9. Heat • Remember – all particles are in motion, and that motion is random • Heat increases the speed of particles, thereby increasing the kinetic energy of the particles • Heat produces “disorderly” motion due to the behavior of the particles

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