Energy forms and Chemical Reactions

1. Energy forms and Chemical Reactions

2. What is energy? • Why study energy when dealing with chemistry? • virtually every physical and chemical change involves some kind of energy change

3. What is energy? 1. What is energy? • the ability to do work 2. When is work done on an object? • when you push or pull it(when you apply a force) thereby moving it some distance when the force is applied to it

5. Examples of Energy • car moving • writing • radios • eating • batting a baseball • throwing a basketball

6. 3. What are the 7 major forms of energy? Electromagnetic Electrostatic Chemical Heat Electrical Magnetic Sound

7. 4. What is the relationship between them? • They are constantly being converted from one form to another 5. Which forms will we deal with most often in chemistry? • Chemical, Heat, Electrostatic, and Electromagnetic

8. 6. Briefly describe these 4 forms and give examples of each.

9. Chemical Energy • Energy trapped in the bonds that hold molecules together • when bonds are broken in chemical reactions-energy is liberated • Examples: methane reaction with oxygen match striking dynamite exploding

10. Heat • Energy that atoms contain. The more energy they contain, the faster they can move, the more force they can exert • Examples: steam powered plants hot air balloons gun shots

11. Electromagnetic Energy • Energy given off and absorbed by the electrons of atoms • some of this energy is visible, most is not • traveling at the speed of light • Examples: Radio waves Television waves visible light xrays

12. Electrostatic • attraction between positive and negative particles • Examples: getting shocked on a cold dry day water rising up a tube(capillary action) explains why substances evaporate at different rates

13. Chemical Energy • Energy trapped in the bonds that hold molecules together • when bonds are broken in chemical reactions-energy is liberated • Examples: methane reaction with oxygen match striking dynamite exploding

14. Forms of Energy • both forms of energy can do work, they can push or pull matter a certain distance • SI unit of energy is the Joule(J) named after the British scientist James Joule who devoted his life to studying forms of energy

15. Energy Unit Conversions

16. James Joule(1818-1889) • student of John Dalton • son of a wealthy brewing family • disproved the idea that heat was a massless fluid • proved that heat was a type of energy that could be used to perform mechanical work

18. The Law of Conservation of Energy 8. What is the Law of Conservation of Energy? • Energy cannot destroyed or created but can be made to change from one form to another

19. Law of Conservation of Energy • scientists have found out that no matter what conversion takes place, the total amount of energy remains the same during the change

20. Albert Einstein’s Contribution • Albert Einstein’s famous Theory of Relativity gave a mathematical relationship between Matter and Energy • E=mc2 where energy is equal to mass traveling at the speed of light squared • in essence if you were to travel at the speed of light you would turn into energy

21. Albert Einstein’s Contribution • Einstein's theory predicted that matter and energy differed in only the speed in which it was traveling • This led to a better understanding of nuclear chemistry, where it was becoming evident that matter could be destroyed • the Laws of Conservation of Matter and Energy were united into one Law

22. Energy & Chemical Reactions 9. What happens during chemical reactions? • one or more substances will be changed into one or more new substances

23. Energy & Chemical Reactions • In the case of the gummie bears, the bears which are mostly made of sugar burns in an oxygen rich compound known as potassium chlorate(KClO3) to produce Carbon dioxide, water, and potassium chloride • C6H12O6 + KClO3--> reactants

24. Energy & Chemical Reactions • In the case of the gummie bears, the bears which are mostly made of sugar burns in an oxygen rich compound known as potassium chlorate(KClO3) to produce Carbon dioxide, water, and potassium chloride • C6H12O6 + KClO3-->CO2 + H2O + KCl • reactantsproducts

25. Energy & Chemical Reactions • in the case of the gummie bears, energy is released by the reaction 10. What do we call a reaction where energy is released? • exothermic

28. Energy & Chemical Reactions • What happened to the Carbon dioxide. • It went from solid phase to gas phase

29. Energy & Chemical Reactions • at the microscopic level it is obvious that in the Carbon dioxide is gaining energy. From where? • Energy is flowing in from the environment.

31. Energy & Chemical Reactions • sometimes energy must be added(continuously) in order for a reaction to occur • when you stop adding energy, the reaction stops proceeding. 11. What do we call a reaction that requires a constant input of energy for it work? • endothermic reaction.

32. 12. Draw Energy diagrams for endothermic and exothermic reactions.

33. Exothermic v Endothermic rxns Reactants Energy Which one has more potential energy: reactants or products? Energy Products Time

34. Exothermic v Endothermic rxns Reactants Energy Reactants! Some of the Energy the reactants had was freed! Energy Products Time Exothermic reaction

35. Exothermic v Endothermic rxns Products Energy Which one has more potential energy: reactants or products? Energy Reactants Time

36. Exothermic v Endothermic rxns Products Energy Products, since the reaction requires energy to be added in order to occur. Energy Reactants Time Endothermic reaction

37. Exothermic v Endothermic rxns Endothermic Exothermic

38. Exothermic v Endothermic rxns Endothermic Exothermic

39. Exothermic v Endothermic rxns Endothermic Exothermic

40. Exothermic v Endothermic rxns Endothermic Exothermic

41. Activation Energy 13. What do we call the energy required to get a reaction started? • this energy is called activation energy 14. Give some examples of activation energy?

42. Activation Energy Examples • scratching a match in order to light it • the use of spark plugs in order to ignite the fuel in your engine cylinders • lighting a piece of paper on fire

44. Heat Measurement and Calorimetry

45. What is the relationship between Heat Energy and Temperature? 15. What is the difference between hot tea and iced tea in terms of energy? • Hot tea has more energy than iced tea?

46. What is the relationship between Heat Energy and Temperature? • 16. In which direction does heat energy always flow? • 17. What do you think will stop heat from flowing? • 18. What happens to an object when heat leaves it? • 19. What happens to an object when heat enters it?

47. What is the relationship between Heat Energy and Temperature? 20. What do thermometer measure? • the heat flow in an object

48. What is the relationship between Heat Energy and Temperature? • Remember: Energy is never lost, it is transferred from one place to another.

49. What is the relationship between Heat Energy and Temperature?

50. Calorimetry 21. What do we call the part of chemistry concerned with the study of the heat flow that occurs during chemical reactions? • Calorimetry