1. Chemical Reactions POPS Chemistry Unit 4 What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

2. What is a chemical Reaction? What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

3. Chemical Reactions Occur when bonds are formed and broken causing substances to recombine into different substances ◦ Reactants = starting substances ◦ Products = ending substances ◦ Arrow always points to the products  Ex: H 2 + O 2 2H 2 O Some Reactions in Progress!

4. Example of Chemical Reactions Zn + 2 HCl → ZnCl 2 + H 2 What are the reactants? Zn and HCl What are the products? ZnCl 2 and H 2

5. How do you know when a chemical reaction takes place? Color Change Precipitate Formation

6. A chemical change: any change in which a new substance is formed. Evidence of a Chemical Change:  Release of energy as heat  Release of energy as light  Change in color  Formation of a gas  Change in odor…

7. Meanings of some symbols

8. What is a chemical Reaction? What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

10. Type of Reaction Definition  Equation Synthesis Decomposition Single Replacement Double Replacement Watch the movie and then complete the chart. A = Red B = Blue C = Green D = Yellow A + B → AB AB → A + B AB + C → AC + B AB + CD → AC + BD Two or more elements or compounds combine to make a more complex substance Compounds break down into simpler substances Occurs when one element replaces another one in a compound Occurs when different atoms in two different compounds trade places

11. Identifying Chemical Reactions ____ P + O 2 → P 4 O 10 ____ Mg + O 2 → MgO ____ HgO → Hg + O 2 ____ Al 2 O 3 → Al + O 2 ____ Cl 2 + NaBr → NaCl + Br 2 ____ H 2 + N 2 → NH 3 2. Use colored pencils to circle the common atoms or compounds in each equation to help you determine the type of reaction it illustrates. Use the code below to classify each reaction. S = Synthesis D = Decomposition SR = Single Replacement DR = Double Replacement

12. ____ Na + Br 2 → NaBr ____ CuCl 2 + H 2 S → CuS + HCl ____ HgO + Cl 2 → HgCl + O 2 ____ C + H 2 → CH 4 ____ KClO 3 → KCl + O 2 ____ S 8 + F 2 → SF 6 ____ BaCl 2 + Na 2 SO 4 → NaCl + BaSO 4

13. What is a combustion A combustion reaction is a type of reaction in which a combustible material combines and generates heat (exothermic reaction).exothermic reaction The reactants are almost always a hydrocarbon and oxygen and the products are almost always carbon dioxide and water General Form of a Combustion Reaction hydrocarbon + oxygen → carbon dioxide + water Example C 10 H 8 + 12 O 2 → 10 CO 2 + 4 H 2 O

14. You Try 1. methane (CH 4 ) + oxygen  2. ethane (C 2 H 6 ) + oxygen  3. propane (C 3 H 8 ) + oxygen  4. butane (C 4 H 10 ) + oxygen 

15. Chemical Reactions What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

16. Law of conservation of Matter States the matter cannot be created nor destroyed. This means that the number of atoms of each type must be the same in the products and the reactants. This means that chemical equations must be balanced.

17. Balancing Equations i.Subscript: # of atoms in that molecule (small #) – cannot change to balance equation ii.Coefficient: # of molecules you have (large #) 1.Ex: 2H 2 + O 2  2H 2 O Subscript Coefficient So there are 2 molecules of 2 hydrogens reacting with 1 molecule of two oxygen to form 2 molecules of water. -Notice that the atoms and the number of atoms are the exact same on both sides.

18. Steps to Balancing an Equation 1. Write all reactants on the left and all products on the right side of the equation arrow. Make sure you write the correct formula for each element. 2. Make a list below both the reactants and the products and list all of the atoms in each element in the equation. Determine if the equation is balanced or not. If it is a balanced equation, it has the same number of atoms of each element on both sides of the arrow. If the equation does not have the same number of atoms of element on both sides of the arrow, then it is not balanced. 3. Use coefficients in front of each formula to balance the number of atoms on each side. Be sure to change the number of atoms in the list below. 4. Multiply the coefficient of each element by the subscript of the element to count the atoms. Then list the number of atoms of each element on each side. 5. It is often easiest to start balancing with an element that appears only once on each side of the arrow. These elements must have the same coefficient. Next balance elements that appear only once on each side but have different numbers of atoms. Finally balance elements that are in two formulas in the same side.

19. Example of how to balance an equation Start with an equation. Mg + O 2  MgO Then all you do is list the atoms that are involved on each side of the arrow Mg + O 2  MgO Mg O Mg O

20. [1] Just count up the atoms on each side Then start balancing: Mg + O 2  MgO Mg O 1 1 1 2 [2] The numbers aren’t balanced so then add “BIG” numbers to make up for any shortages And adjust totals Mg + O 2  MgO Mg O 1 1 1 2 2 2 2

21. Mg + O 2  MgO Mg O 1 2 2 2 2 But the numbers still aren’t equal, so add another “BIG” number 2 And adjust totals again NOW BOTH SIDES HAVE EQUAL NUMBERS OF ATOMS WE SAY THAT THE EQUATION IS BALANCED!! 2

22. Try to balance these equations using the same method: [1] Na + Cl 2  NaCl [2] CH 4 + O 2  CO 2 + H 2 O [4] Al + O 2  Al 2 O 3 [3] Li + HNO 3  LiNO 3 + H 2

23. How did you get on?? [1] 2 Na + Cl 2  2 NaCl [2] CH 4 + 2 O 2  CO 2 + 2 H 2 O [4] 4 Al + 3 O 2  2 Al 2 O 3 [3] 2 Li + 2 HNO 3  2 LiNO 3 + H 2 Here are the answers:

24. Chemical Reactions What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

25. 25 Oxidation reactions are always accompanied by a reduction reaction Oxidation - originally meant combining with oxygen - iron rusting (iron + oxygen) Reduction - originally meant the loss of oxygen from a compound removing iron from iron ore ( iron II oxide)

26. 26 20.2 Electron Transfer in Redox Reactions Today OXIDATION means: - a complete or partial LOSS of ELECTRONS REDUCTION means: - a complete or partial GAIN of ELECTRONS Memory Device : LEO the lion says GER or OIL RIG

27. 27 The substance that donates electrons in a redox reaction is the REDUCING AGENT The substance that takes electrons in a redox reaction is the OXIDIZING AGENT

28. 28 Oxidation is… –the loss of electrons –an increase in oxidation state –the addition of oxygen –the loss of hydrogen 2 Mg + O 2  2 MgO notice the magnesium is losing electrons Reduction is… –the gain of electrons –a decrease in oxidation state –the loss of oxygen –the addition of hydrogen MgO + H 2  Mg + H 2 O notice the Mg 2+ in MgO is gaining electrons

29. 1)2 Na + FeCl 2  2 NaCl + Fe 2)2 C 2 H 2 + 5 O 2  4 CO 2 + 2 H 2 O 3)2 PbS + 3 O 2  2 SO 2 + 2 PbO Let’s Practice

30. How did you do? 1)2 Na + FeCl 2  2 NaCl + Fe Sodium is oxidized, going from a 0 to +1 oxidation state. Iron is reduced, going from a +2 to 0 oxidation state. 2)2 C 2 H 2 + 5 O 2  4 CO 2 + 2 H 2 O Carbon is oxidized, going from a –1 to +4 oxidation state. Oxygen is reduced, going from a 0 to –2 oxidation state. 3)2 PbS + 3 O 2  2 SO 2 + 2 PbO Sulfur is oxidized, going from a –2 to +4 oxidation state. Oxygen is reduced, going from a 0 to –2 oxidation state.

31. Chemical Reactions What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

32. What is an acid? An acid is a solution that has an excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour". The more H + ions, the more acidic the solution.

33. Properties of an Acid Tastes Sour Conduct Electricity Corrosive, which means they break down certain substances. Many acids can corrode fabric, skin, and paper Some acids react strongly with metals Turns blue litmus paper red Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml

34. Uses of Acids Acetic Acid = Vinegar Citric Acid = lemons, limes, & oranges. It is in many sour candies such as lemonhead & sour patch. Ascorbic acid = Vitamin C which your body needs to function. Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. Car batteries

35. What is a base? A base is a solution that has an excess of OH- ions. Another word for base is alkali. Bases are substances that can accept hydrogen ions

36. Properties of a Base Feel Slippery Taste Bitter Corrosive Can conduct electricity. (Think alkaline batteries.) Do not react with metals. Turns red litmus paper blue.

37. Uses of Bases Bases give soaps, ammonia, and many other cleaning products some of their useful properties. The OH- ions interact strongly with certain substances, such as dirt and grease. Chalk and oven cleaner are examples of familiar products that contain bases. Your blood is a basic solution.

38. pH Scale pH is a measure of how acidic or basic a solution is. The pH scale ranges from 0 to 14. Acidic solutions have pH values below 7 A solution with a pH of 0 is very acidic. A solution with a pH of 7 is neutral. Pure water has a pH of 7. Basic solutions have pH values above 7.

39. pH Scale A change of 1 pH unit represents a tenfold change in the acidity of the solution. For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second— it is ten times more acidic.

40. Acid – Base Reactions A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.

41. Neutralization Reactions An acid base reaction often produces water and salt. The general form of a acid base reaction is Acid + Base Salt +water Example HCl + NaOH NaCl + H 2 0 Each salt listed in this table can be formed by the reaction between an acid and a base. Can you guess which acids and bases were the reactants?

42. Chemical Reactions What is a chemical reaction What are the different types chemical reactions How to balance a chemical reaction Oxidation/ Reduction Reactions Acid and bases reactions Applications

43. Some Important Equations To Know Equation for Photosynthesis 6CO 2 + 6H 2 O Light Chlorophyll C 6 H 12 O 6 +6O 2 Equation for Cell Respiration C 6 H 12 O 6 +6O 2 6CO 2 + 6H 2 O +Energy +Heat

44. Chemical reactions happen when a car is started tarnish is removed from silver fertilizer is added to help plants grow food is digested electricity is produced from burning natural gas rust is formed on iron nails

45. Everything in our lives from materials to life involve chemistry glass (SiO 2 ) n metal alloys chemically treated water plastics and polymers baking soda, NaHCO 3 foods fertilizers and pesticides living beings

46. Chemicals in Toothpaste

47. Chemistry is Cool!