1.  Update your Table of Contents  Write your homework – leave it to be stamped  Get your Adopt-An-Element Baby Book AND get ready to grade it!  We will grade your tests next class! WARM – UP: A-day DateSession # ActivityPage # 10/10- 10/11 17 Balancing Act Note Guide 27 Practice Equations – (hand copy into your notebook from the slides!) 28

2.  Update your Table of Contents  Write your homework – leave it to be stamped  Get something to grade your test! WARM – UP: B-day DateSession # ActivityPage # 10/10- 10/11 17 Balancing Act Note Guide 27 Practice Equations – (hand copy into your notebook from the slides!) 28

3. Physical & chemical changes can change matter, BUT…THE BIG QUESTION Is: During those changes, is any matter created or destroyed?

4. Law of Conservation of Mass (Matter) Law of Conservation of Mass (Matter)- Matter cannot be created or destroyed, it can only change form So where does the wood go?

5. NaF NaF In other words, what goes in, must come out!

6. Chemical Reactions Reactants – Elements present at the beginning of a chemical reaction Product – Compounds formed by a chemical reaction

7. REACTANTSREACTANTS PRODUCTPRODUCT

8. NaF NaF The arrow indicates that a chemical reaction has occurred

9. Balancing Chemical Equations  Since matter can neither be created or destroyed, the mass/amount of reactants must always equal the mass/amount of products

10. Balancing Chemical Equations  Before (Reactants)  After (Product) Na F = 1 NaF Na = 1 F F = 1

11.  STOP, THINK, DISCUSS…  If you weigh your reactants before a chemical reaction, and the products afterwards and they DO NOT have the same mass before and after what likely happened during the chemical reaction? (Hint: Think about the wood burning in the fireplace) But What If It Doesn’t?

12.  As you watch the dry ice demo write ANY observations! (5 senses)  Explain how this demonstrates The Law of Conservation of Mass! Dry Ice Demo

13.  Freezing Point of Carbon Dioxide = -108.4 o F or -78 o C  Boiling Point of Carbon Dioxide = -76 o F or -57 o C  Formula: CO 2 (s) CO 2 (g) Dry Ice Demo Dry Ice = Solid Carbon Dioxide

14. Law of Conservation of Mass (Matter) Lab Investigation Roles  Group Leader – Responsible for reading and making sure the group is following directions accurately and completing all parts of the lab  Supply Manager – gets and returns supplies and makes sure they are clean -assists measurement technician in calibrating the scale  Measurement Technician – gets and returns the scale balance and is responsible for accurate mass measurements  Data Discussion Technician – makes sure the group records the mass data before and after the experiment, AND has an explanation for BOTH THE TEACHER DEMO AND STUDENT LAB

15. Law of Conservation of Mass (Matter) Lab Investigation  Send your supply manager to get the lab kit from the front counter and measurement technician to get the scale balance from the back counter  Group leader, read the directions carefully each step of the way!! ◦ WARNING: YOUR BALLOON IS ALREADY FULL OF BAKING SODA, DO NOT TIP IT INTO THE GRADUATED CYLINDER ACCIDENTALLY!

16. Law of Conservation of Mass (Matter) Lab Investigation Clean-Up  Balloons in the garbage  Rinse graduated cylinder thoroughly  Wipe up any spills  Put all items back into your lab kit & put them on the front counter  Put scale balance back onto the back counter  Make sure every group member has measurements and an explanation for BOTH THE STUDENT LAB AND THE TEACHER DEMO – WORK ON THE COMPARE & CONTRAST TOGETHER!

17.  Again, the explanation should state how this experiment demonstrated the Law of Conservation of Mass…BUT,  What were the similarities and differences between the teacher demo and the student mini lab? Compare & Contrast

18. 2H 2 + O 2 2H 2 O  (Reactants)(Products) Chemical formulas for elements Chemical formula for new compound Subscripts Coefficient Subscript

19. What is that little number? Subscript – ◦ Shows how many atoms of an element are in a compound. ◦ When there is NO subscript there is only 1 atom of that element. O2O2 NH 4 NaClK5N4C2K5N4C2

20. What is that big number in front? Coefficient – ◦ The number of molecules (compounds) involved in a chemical reaction H2H2 H2H2 O2O2 H2H2 O2O2 H2OH2O 2 2

21. So the coefficient tells you the number of molecules, but what about each atom?  You must multiply…it is like the distributive property in math! 2NH 4 5H 2 O 2Li 3 F 2 4NaCl2K 5 N 4 C 2 3O 2

22. Rules for Balancing Chemical Equations 1. You CANNOT change subscripts, you can ONLY change coefficients H 2 + O 2 2H 2 O 2. It does NOT have to look the same on both sides, it only has to be balanced 3. You CANNOT split compounds to write in a coefficient: HCl 2

23. Rules to Balancing Chemical Equations 4. Only multiply through when it is a compound because they have already bonded 2H + Cl 2HCl NOYES 5. If it is a capital letter, they are each a separate element: H, C, O If it is a capital letter followed by a lower case letter, it is all one element: Cl, Li, Si

24. Steps for Balancing Chemical Equations  1. Divide the reactants from the products with a line.  2. Write down the chemical symbol of each of the elements on each side of the equation 2 H 2 + O 2 2H 2 O H = O = H = O =

25. Steps to Balancing Chemical Equations  3. Using the coefficients and subscripts write down the number of each element  4. If they are not balanced change the coefficients using trial and error. You will have to go back and forth between each side! 2 H 2 + O 2 2H 2 O H = 4 O = 2 H = 4 O = 2

26. Lets Practice P + O 2 P4O6P4O6

27. Lets Practice Na + O 2 Na 2 O

28. Lets Practice Al 2 O 3 Al + O 2

29. Lets Practice Cl 2 + KIKCl + I 2

30.  Update your Table of Contents  Write your homework – leave it to be stamped  Get something to grade your test with! WARM – UP: A-Day DateSession # ActivityPage # 10/14 - 10/15 18 Law of Conservation of Mass Note Guide 29 Balancing Equations Practice 30

31.  Update your Table of Contents  Write your homework – leave it to be stamped  Get your “Baby” out and we will grade your Baby Book using the rubric on your desk! WARM – UP: B-Day DateSession # ActivityPage # 10/14 - 10/15 18 Law of Conservation of Mass Note Guide 29 Balancing Equations Practice 30

32.  Complete the Warm- Up/Review section at the top of your note guide. Warm-Up Review

33. REVIEW  LAW OF CONSERVATION OF MASS (MATTER)

34. Law of Conservation of Mass (Matter) Law of Conservation of Mass (Matter)- Matter cannot be created or destroyed, it can only change form In other words… What goes in, must come out!

35. Law of Conservation of Mass (Matter) Analyzing Reactions  Some chemical reactions are ENDOTHERMIC = take “in” or absorb energy  Some chemical reactions are EXOTHERMIC = give “out” or produce energy How would you tell the difference?

36. Endothermic Reactions  An endothermic reaction takes “in” or absorbs energy  Causes temperature around it to cool (will feel cold)  They are forming a chemical bond which requires energy to occur  EXAMPLE: Photosynthesis (needs energy from the sun)

37.  An exothermic reaction gives “out” or produces energy (heat, light or sound)  Causes temperature around it to rise (feels warm/hot)  They are breaking a chemical bond which releases energy  EXAMPLE: cellular respiration (gives energy to your cells) Exothermic Reactions

38. Endo & Exo Lab Investigation Roles  Group Leader – Responsible for reading and making sure the group is following directions accurately and completing all parts of the lab  Supply Manager – gets and returns supplies and makes sure they are clean  Data Discussion Technician – makes sure the group records all observations and has an explanation for BOTH investigations!  Speaker – Group member that must share your explanation/conclusion with the class.

39. REVIEW  BALANCING EQUATIONS…Please get your Rules & Steps for balancing equations out!

40. Rules for Balancing Chemical Equations 1. You CANNOT change subscripts, ONLY coefficients H 2 + O 2 2H 2 O 2. It does NOT have to look the same on both sides, it only has to be balanced 3. You CANNOT split compounds to write in a coefficient: HCl 2

41. Rules to Balancing Chemical Equations 4. Only multiply through when it is a compound because they have already bonded 2H + Cl 2HCl NOYES 5. If it is a capital letter, they are each a separate element: H, C, O If it is a capital letter followed by a lower case letter, it is all one element: Cl, Li, Si

42. Steps for Balancing Chemical Equations  1. Divide the reactants from the products with a line.  2. Write down the chemical symbol of each of the elements on each side of the equation 2 H 2 + O 2 2H 2 O H = O = H = O =

43. Steps to Balancing Chemical Equations  3. Using the coefficients and subscripts write down the number of each element  4. If they are not balanced change the coefficients using trial and error. You will have to go back and forth between each side! 2 H 2 + O 2 2H 2 O H = 4 O = 2 H = 4 O = 2

44. Back to Page 28: Lets Do a Few Together… Cl 2 + KIKCl + I 2

45. Lets Do a Few Together… CH 4 + O 2 CO 2 + H 2 O

46. Lets Do a Few Together… Li + H 2 OLiOH + H 2

47.  Complete the Practice Worksheet

48. Copy these 3 questions, and then answer them in complete sentences for 5 points extra credit! 1. What does the Law of Conservation of Mass (Matter) state, and what does that really mean? 2. Explain how either the dry ice demo or the balloon experiment from last class demonstrated the Law of Conservation of Mass (Matter)? 3. How is the Law of Conservation of Mass (Matter) the key to balancing chemical equations? Extra Credit: Sum It Up!