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Thermochemistry

Thermochemistry. Energy. Energy – the ability to do _________ or produce _________ Exists in 2 forms: Kinetic energy – energy of _________ Potential energy – energy at _________ or energy of _________ . Energy. Kinetic energy – in a chemical reaction _________ is the determining factor

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Thermochemistry

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  1. Thermochemistry

  2. Energy • Energy – the ability to do _________ or produce _________ • Exists in 2 forms: • Kinetic energy – energy of _________ • Potential energy – energy at _________ or energy of _________

  3. Energy • Kinetic energy – in a chemical reaction _________ is the determining factor • The higher the temperature…the _________ the particles move…the _________ the kinetic energy • Potential energy – in a chemical reaction deals with the types of atoms & what bonds the form

  4. Law of Conservation of Energy • Law of Conservation of Energy – Energy is neither _________ nor _________

  5. Heat (q) • Heat or energy can be in joules, calories, kilocalories, or kilojoules • The SI unit is the _________ • 1 cal = 1000 Cal • 1 cal = 4.18 J

  6. Specific Heat • _____________(c) – the amount of heat required to raise 1 gram of a substance by 1C • Specific heat is an _________ property • Every substance has its own specific heat

  7. Specific Heat • q = mcT • q = heat (J) • m = mass (g) • c = specific heat (j/gC) • T = change in temperature = Tf-Ti (C)

  8. Specific Heat • A 10.0 g sample of iron changes temperature from 25.0C to 50.4 C while releasing 114 joules of heat. Calculate the specific heat of iron.

  9. Another example • If the temperature of 34.4 g of ethanol increases from 25.0 C to 78.8 C how much heat will be absorbed if the specific heat of the ethanol is 2.44 J/g C

  10. Yet another example • 4.50 g of a gold nugget absorbs 276 J of heat. What is the final temperature of the gold if the initial temperature was 25.0 C & the specific heat of the gold is 0.129J/g C

  11. Endothermic & Exothermic Reactions • Endothermic reactions – chemical reaction that requires energy to break existing bonds • Heat goes _________ the reaction from the surroundings • Exothermic reactions – chemical reaction in which energy is released • Heat goes _________ of the reaction into the surroundings

  12. Endothermic & Exothermic Reactions • Endothermic reactions – since heat goes from the surroundings into your system, it will feel _________ • Temperature of endothermic reactions goes _________ • The sign for the heat change will be _________ • Exothermic reactions – since heat goes from the system to the surroundings, it will feel _________ • Temperature of exothermic reactions goes _________ • The sign for the heat change will be _________

  13. Endothermic & Exothermic Reactions

  14. Endothermic & Exothermic Reactions

  15. Endothermic & Exothermic Reactions • Are the following reactions endothermic or exothermic? • CO + 3H2 CH4 + H2O H= -206kJ • I add magnesium metal to some hydrochloric acid. The temperature goes from 23C to 27 C • I mix together some vinegar & baking soda. The temperature goes from 28C to 23C

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