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Heat Calculations with Specific Heat

Heat Calculations with Specific Heat. What is heat? What is energy? How are they both measured?. What is heat?. (q) – transfer of energy from one object to another because of temperature difference between objects form of energy flows from warmer to cooler object measured in joules.

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Heat Calculations with Specific Heat

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  1. Heat Calculations with Specific Heat What is heat? What is energy? How are they both measured?

  2. What is heat? • (q) – transfer of energy from one object to another because of temperature difference between objects • form of energy • flows from warmer to cooler object • measured in joules

  3. What is energy? • (E) – ability or capacity to do work • measured in joules • detected by effects

  4. What is temperature? • (T) – NOT a form of energy • thought of as intensity of heat • measured in C, F, or K • amount of heat per unit of substance

  5. What is a Joule? • (J) – amount of energy produced when a force of 1 Newton acts over a distance of 1 meter • small amount of energy • 1 Newton ~ amount of force 40 pennies exerts on the palm of your hand • striking a match releases 1050 J

  6. What is thermodynamics? • THERMODYNAMICS deals with energy changes (∆ E) that accompany chemical and physical properties • TELL US whether a reaction is possible depending on: - whether reaction occurs by itself (spontaneously) OR - if reaction needs outside source of energy to proceed

  7. Laws of Thermodynamics

  8. What is heat capacity? • energy required to raise temperature of substance by 1 °C • Every pure substance has unique heat capacity • Expressed as Joules • 1 Calorie = 4.184 Joule

  9. What is specific heat? • (Cp) energy required to raise temperature of substance by 1 °C • Specific Heat varies depending on: • Type of substance • State of matter of substance (s, l, g) • Temperature of the reaction • S.H. of ICE = 2060 J/kg°C • S.H. of liquid water = 4180 J/kg°C

  10. How do you measure heat? 1. Mathematically using HEAT EQUATION • q = m x Cp x ∆T • How much energy would be needed to heat .450 kg of Copper metal from a temperature of 25 °C to 75 °C? • Specific Heat of Copper at 25 °C = 385 J/kg °C • q = m (Cp) ∆T PLUG AND CHUG!

  11. What is a Calorimeter?

  12. You are boiling water to make spaghetti. When the water boils, does it all instantly vaporize? Why not, after all – it’s reached the boiling point? • Video Animation

  13. Heating Curve in Motion

  14. EX. How much heat is necessary to totally melt 5 g of ice at 0 C to liquid water at 0 C? • EX. How much heat is necessary to change 5 g of water at 100 C to steam at 100 C? • HEAT CALCULATIONS  • q = m Cp△T for substance WITHOUT a phase change • q = m △Hfuswhen a substances freezes/melts • q = m △Hvapwhen a substance evaporates/condenses • If a substances undergoes a phase change and changes temperature, you must add all the heats together.

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