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Section One Energy

Section One Energy Energy : is the capacity to do some kind of work, such as moving an object. Examples: No matter how energy is defined, it is always involved when there is a change in matter. (Kinetic Energy: energy of motion) (Potential Energy: stored energy)

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Section One Energy

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  1. Section One Energy Energy: is the capacity to do some kind of work, such as moving an object. Examples: No matter how energy is defined, it is always involved when there is a change in matter. (Kinetic Energy: energy of motion) (Potential Energy: stored energy) (Joule :unit of energy see Reference Tables) Ex:8kJ= ?J 1kJ=1000J

  2. Changes in matter can be physical or chemical Every change in matter involves a change in energy The melting of ice and the boiling of water are 2 ex of phy changes that are endothermic process. Some chemical changes are also endo. Endothermic: a process in which heat is always absorb; cooler to touch ** word heat/energy/#’s on reactant side of equation H2O(s) + heat  H2O(l) H2O(l) + energy  H2O(g)

  3. Any change in matter when heat is released is exothermic, get hotter ** heat/energy/#’s on product side Energy is either absorbed or given off during a phy or chem change A + B  C +energy A + B+ energy  C Exo endo

  4. Lavoisier worked on the Law of Conservation of Energy. Defined: Energy cannot be created nor destroyed it’s rearranged. Heat is the energy transferred between objects that are at different temperatures. Heat is transferred (flows) from a higher temperature object to a lower temperature until thermal equilibrium s reached. Temperature: measures the average Kinetic Energy of the random motion of particles in a substance.

  5. Temperature scales based on marking a thermometer would need: a boiling point, freezing point, find the difference between the two temperatures, and make a range to space out even. Temperature scales: Celsius scale 0 c (fpt/mpt of water) to 100c (bpt of water) Kelvin Scale 273K (fpt/mpt of water) to 373K (bpt of water)

  6. Converting Table T K= C + 273 C= K -273 Range on both scales is 100 Ex:1 if temp changes 25c, how much will it change on the Kelvin scale? 25K Ex 2: 47K=?C 52C=?K -226c 325K Absolute zero: coldest possible temperature all motion stops. 0K -273C

  7. Terms • Melting: sl endo Heat of Fusion • Freezing: ls exo Heat of Crystallization • Boiling lg endo • Condensation: gl exo • Sublimation: sg no l phase endo H2O(s) H2O(g) CO2(s) CO2(g) I2(s) I2(g)

  8. Specific Heat Table T q=mc T Table B Specific Heat Capacity of Water 4.18 J/g*K(c) Ex#1 a 2,000g sample of water is heated to 3c. How much heat is produced?

  9. Ex#2 A 500. g sample of water had a temperature change from 10.c to 15c. How much heat was produced?

  10. q=mc^T 40.0g x 4.18J/gc x 20.0c = 3,344J~3,340J 2. q=mc^T 65.6gx 4.18J/gc x 16.2c= 4,442J ~4,440J 3. q=mc^T 275g x 4.18J/gc x 88.0c= 101,156J~101,000J 4. q=mc^T 25g X 4.18J/gc X 45.0c= 4,703J~4,700J

  11. 5. q=mc^T 135.6g x 4.18J/gc x 74.2c= 42,057J~42,100J Back 1. q=mc^T 2,000.gx 4.18 x 3.0 =25,080~25,000J 5. q=mc^T q=100.g x .129J/gC X 14C=181J~180J

  12. 6. q=mc^T Q=250.g x 4.18J/gC x 60.C= 62,700J~63,000J 7. q=mc^T 5,000.g x 4.18J/gC x 60.C=1,254,000J~1,300,000J

  13. Ex#3 A sample is heated from 20C to 100c as 70,000j of heat is released. How many grams of water were heated? Ex#4 A 2,000g sample of water whose temperature was 50C lost 33,600J of heat over a ten minute period. What was the temperature of the water at the end?

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