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Published byBruno Tucker Modified over 8 years ago
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ENERGY
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Energy Ability to do work Kinetic Energy Energy of motion Potential Energy Stored energy Temperature Measure of the Average Kinetic Energy of the particles of a sample vs. Heat Kinetic energy of the particles (always flows from hot to cold)
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Temperature Scales in Science Celsius : – The lowest point on the scale is -273.15 °C Absolute Zero Kelvin: – The lowest point on the scale is 0K Absolute Zero
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NEVER, EVER USE FAHRENHEIT IN SCIENCE!!!!! IT IS THE “F” WORD!!!
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What is Absolute Zero? The point at which no more heat can be removed from a system Almost no movement of molecules Theoretical temperature
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Temperature Conversions Table T K= °C + 273 °C = K-273 (this is not on the table)
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Energy Changes In a chemical or physical change there may be a transfer of energy (heat) Exothermic process: there is a release of energy (heat) Endothermic process: there is absorption of energy (heat)
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Energy changes Exothermic Reactions will feel “hot” Endothermic Reactions will feel “cold”
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What is heat? Bill Nye The Science Guy on Heat
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Heating and Cooling Curves Shows the heating or the cooling of a specific substance Heat is added at a constant rate When a substance is undergoing a phase change THE TEMPERATURE DOES NOT CHANGE until the phase change is complete
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Phase changes (Vocabulary) Melting (Fusion) Vaporization (l-g) Sublimation (solid gas) Deposition (gas solid) Freezing (fusion) Condensation (g-l)
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Time (minutes) T e m p er at ur e ( ◦ C ) SOLID LIQUID GAS Melting Point Boiling Point Endothermic
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Time (minutes) T e m p e r a t u re ( ◦ C) SOLID LIQUID GAS Freezing Point Condensation Point Exothermic
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Time (minutes) T e m p er at ur e ( ◦ C ) Δ Kinetic Energy Kinetic Energy is constant
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Time (minutes) T e m p er at ur e ( ◦ C ) Δ Potential Energy Potential Energy is constant
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Time (minutes) T e m p er at ur e ( ◦ C ) q = mCΔT q = mH f q = mH v
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Law of Conservation of Energy In any chemical or physical process, energy is neither created nor destroyed, it is merely transferred.
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How is heat measured? Calorimetry – The precise measurement of heat flow into or out of a system. – The heat released by a system is equal to the heat absorbed by its surroundings – The heat absorbed by a system is equal to the heat released by the surroundings – A calorimeter is an insulated device used to measure the absorption or release of heat
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Constant Pressure Calorimeter Most changes in the lab occur at constant pressure The heat of a system is it’s enthalpy (H) The heat released or absorbed by a system at constant pressure is equal to the system’s change in enthalpy (ΔH ) ΔH = q q= mC ΔT mass Specific heat Heat Change in temperature (Final Temperature – Initial Temperature)
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ΔHΔHProcessHeat Positive (Final Temperature is higher than the initial temperature) EndothermicAbsorbed Negative(Final Temperature is lower than the initial temperature) ExothermicReleased
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Calorimetry
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