WARM – UP: A-day

1. WARM – UP: A-day • 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!

2. WARM – UP: B-day • Update your Table of Contents • Write your homework – leave it to be stamped • Get something to grade your test!

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. Law of Conservation of Mass is the KEY to Balancing Equations! NaF Na F In other words, what goes in, must come out!

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

7. REACTANTS PRODUCT

8. What are the Reactants?What are the Products? NaF Na F 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. Before (Reactants) After (Product) Balancing Chemical Equations NaF Na F Na = 1 Na = 1 F = 1 F = 1

11. But What If It Doesn’t? • 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)

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

13. Dry Ice Demo Dry Ice = Solid Carbon Dioxide • Freezing Point of Carbon Dioxide = -108.4oF or -78oC • Boiling Point of Carbon Dioxide = -76oF or -57oC • Formula: CO2(s) CO2(g)

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. Compare & Contrast • 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?

18. Components of a Chemical Equation(Label your diagram) Chemical formula for new compound Chemical formulas for elements  2H2 + O2 2H2O Coefficient Subscript Coefficient Subscripts (Reactants) (Products)

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. O2 NaCl NH4 K5N4C2

20. What is that big number in front? Coefficient – • The number of molecules (compounds) involved in a chemical reaction H2 O2 H2 H2O 2 2 H2 O2

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! 2NH4 5H2O 3O2 2Li3F2 4NaCl 2K5N4C2

22. Rules for Balancing Chemical Equations 1. You CANNOTchange subscripts, you can ONLY change coefficients H2 + O2 2H2O 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 NO YES 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 H2 + O 2 2H2O 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 H2 + O 2 2H2O H = 4 O = 2 H = 4 O = 2

26. P + O2 P4O6 Lets Practice

27. Na + O2 Na2O Lets Practice

28. Al2O3 Al + O2 Lets Practice

29. Cl2 + KI KCl + I2 Lets Practice

30. WARM – UP: A-Day • Update your Table of Contents • Write your homework – leave it to be stamped • Get something to grade your test with!

31. WARM – UP: B-Day • 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!

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

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. Exothermic Reactions • 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)

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 H2 + O2 2H2O 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 NO YES 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 H2 + O 2 2H2O 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 H2 + O 2 2H2O H = 4 O = 2 H = 4 O = 2

44. Cl2 + KI KCl + I2 Back to Page 28:Lets Do a Few Together…

45. CH4 + O2 CO2 + H2O Lets Do a Few Together…

46. Li + H2O LiOH + H2 Lets Do a Few Together…

47. Complete the Practice Worksheet

48. Extra Credit: Sum It Up! 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?