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Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
Energy & Reactions
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Energy & Reactions

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A set of slides created to teach Energy & Reactions to learners at Bishops Diocesan College in Cape Town.

A set of slides created to teach Energy & Reactions to learners at Bishops Diocesan College in Cape Town.

Published in: Education, Technology, Business
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  • 1. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Bonding & Energy K Warne
  • 2. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Bonding O H2O O H2O O O Two hydrogen molecules and one oxygen molecule react to form two water molecules. Two H-H single bonds One O=O double bond Four H-O single bonds BONDS BROKEN 2x H-H single bonds 1x O=O double bond BONDS FORMED 4x O-H single bonds 2 H2 + O2  2 H2O +
  • 3. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY e- Bonding Theory Why do atoms join together? e- e- ? e- The nucleus of one atom attracts the electrons from the other atom.
  • 4. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Bonding Theory e- e- e- e- • Atoms are attracted to each other as the protons from one atom attract the electrons from another atom. • As two atoms approach each other the energy of the system drops. • When the atoms get close enough for the nuclei to begin repelling the energy begins to increase. • If the atoms were forced closer the energy of the system would rise sharply. e-e-
  • 5. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY 74 100 200 H-H bond length pm (x10-12 m) 0 -100- -200- -300- -400- -432- -500-  Bond Energy & Length 1. Atoms are attracted to each other as the protons from one atom attract the electrons from another atom. 2. As two atoms approach each other the energy of the system drops. 3. When the atoms get close enough for the nuclei to begin repelling the energy begins to increase. 4. If the atoms were forced closer the energy of the system would rise sharply. The bond is stable when the minimum energy system is reached.
  • 6. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Bond Enthalpies + Whenever a bond is formed ENERGY ____________. Whenever a bond is BROKEN ENERGY is _________. Bond FORMING – _______________. Bond BREAKING – ________________. Bond Energy: The energy __________ to break a bond. (kJ.mol-1) Stronger bonds _______________ bond energy.
  • 7. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Exothermic Reactions Reaction gives off energy to the surroundings – surroundings get HOT!
  • 8. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Exothermic Reactions Reaction ________________ the surroundings – _____________________!
  • 9. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Exothermic Reactions Reaction gives off energy to the surroundings – surroundings get HOT! 540 kJ Energy 140 kJ Energy released = 140 – 540 = -400 kJ Energy of REACTION = ENERGY OF PRODUCTS– ENERGY OF REACTANTS ΔHr = ΔHP - ΔHR ΔHr for EXOTHERMIC is ALWAYS NEGATIVE!
  • 10. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Exothermic Reactions Reaction gives off energy to the surroundings – surroundings get HOT! Energy needed to ................... all bonds. Energy released when ............... bonds ................... ΔHreaction = E............................ – E................................. ΔHreaction ....... 0 (i.e. ...................) ΔHreaction H = internal Heat Energy or ENTHALPY E = ................ ENERGY ΔHr= Ebreaking – E forming = ........– ........= ......... kJ 100kJ 640kJ
  • 11. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY (a) Energy needed to ................ all bonds. Endothermic Reactions Reaction takes energy from the surroundings – surroundings get cold! Reactants Products Activated Complex (b) Energy released when .................................. (c) (a) (b) ΔHreaction = Eproducts– Ereactants = .........– .........= .......kJ ΔHreaction .... 0 (i.e. ...............) ΔHreaction 140kJ 540kJ ΔHreaction = Ebreaking– Eforming = ......– ........= ..........kJ ΔHreaction ...... 0 (i.e. ...............) 600kJ Activation energy 200kJ 400 kJ Or ΔHr ....... 0 Overall ........... energy taken in than given out!
  • 12. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Bond Length (pm) Energy (kJ/mol) Bond Length (pm) Energy (kJ/mol) H--H 74 436 H-C 109 413 C-C 154 348 H-N 101 391 N-N 145 170 H-O 96 463 O-O 148 145 H-F 92 568 F-F 142 158 H-Cl 127 432 Cl-Cl 199 243 H-Br 141 366 Br-Br 228 193 H-I 161 298 I-I 267 151 C-C 154 348 C-C 154 348 C=C 134 614 C-N 147 308 CC 120 839 C-O 143 360 O-O 148 145 C-S 182 272 O=O 121 498 C-F 135 488 N-N 145 170 C-Cl 177 330 C=O 120 799 C-Br 194 288 Can you identify any TRENDS or PATTERNS in this data?
  • 13. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Bond Energy & Length Bond FORMING – EXOTHERMIC. Bond BREAKING – ENDOTHERMIC. Bond Energy: E (kJmol-1) • The amount of energy ____________ ______________________________ • Given out when a bond is _________. • Taken in when bond is ___________. PotentialEnergy Distance between nuclei Bond Length: d (nm) • The distance between ___________ _____________________________. • _________ when bonds STRONGER. • ___________ when bonds WEAKER. e- e- e- e-
  • 14. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Energy Changes During Reactions ΔHr = Hprod – HReact = Ebreaking– Eforming PotentialEnergy PotentialEnergy H prod Hreact H prod H react You can determine ΔHr in TWO different ways. The equation you use depends on the information you are given. ΔHr > 0 ΔHr < 0 Hbreaking Hforming Hbreaking Hforming Given ENTHALPYS given BOND ENERGIES
  • 15. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Bond Energy Calculations H2 + Cl2  2H-Cl H H Cl Cl H H Cl Cl H H Cl Cl Activated complex Bonds Breaking/Forming ΔHreaction = Ebreaking– Eforming = = …… – ……. = …….kJ ΔHreaction > …… (i.e. ………….) Look up the required bond energies: E (H-H) = E (Cl-Cl) = E (H-Cl) =
  • 16. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Bond Energy Examples Use data from the bond energy table to calculate the enthalpy of reaction for the following reactions: (per mol of the first element in each reaction) 1. O2 + 2 H2  2H2O (no 4 TT) 2. CH4 + O2  CO2 + H2O 3. CH3CH2OH + O2  CO2 + H2O OC C H H H H H H C H H H H
  • 17. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Calculate H r
  • 18. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Born Haber Cycle A large amount of energy (lattice) is released when the gaseous ions bond together into the ionic crystal lattice. Ionic compounds are therefore very stable and require large amounts of energy to break the bonding. Ionic compounds have HIGH MELTING POINTS we say they are thermally stable. Na(s) + 1/2 Cl2(g) NaCl(s) Na(g) + 1/2 Cl2(g) Na(g) + Cl(g) Na+ (g) + e- + Cl(g) Na+ (g) + Cl- (g) Ionisation Energy Dissociation Energy Sublimation Energy Electron Affinity Lattice Energy
  • 19. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY Hi - This is a SAMPLE presentation only. My FULL presentations, which contain a lot more more slides and other resources, are freely available on my resource sharing website: www.warnescience.net (click on link or logo) Have a look and enjoy! WarneScience

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