1. After The Test
For Extra Credit Write 10 Compound Formulas Using Only Your Periodic Table and Write The Correct Name For Each Of Them

2. Chemical Reactions

3. Today MIXTURE LAB IS DUE
Physical Chemical Changes Lab (Done In Class Today):
REMEMBER ONE SET OF CUPPLIES FOR EACH TABLE
For step 1.b) use on splint
For step 2.e) put the waste into the beaker in the fume hood
For step 2. f) do not do the second heating
For step 3. f) put the waste into the beaker in the fume hood
For step 4 (all) do this part fast so the reactions work. BE PREPARED READ THE WHOLE part 4 BEFORE YOU BEGIN
For step 4.c) put the waste into the beaker in the fume hood
DENSITY LAB : Due to lack of chrome book contracts complete the density lab up until the “Observations and Data Part 2” this will be due Friday (10/30/15).

4. DO NOW
In your lab you mixed solid zinc with hydrochloric acid to produce hydrogen gas and aqueous zinc chloride. Write the formulas for all of the chemicals listed in the reaction and arrange them in a way that makes sense to you.

6. Chemical Reactions A chemical change is really a chemical reaction.
Four signs a chemical change has occurred:
color change
formation of a precipitant
evolution of a gas
spontaneous change in temperature

7. Color Change

8. Formation of a Precipitant

9. Formation of a Gas

10. Spontaneous Temperature Change

11. Chemical reaction
Chemical reaction- bonds (attraction between atoms) are broken, atoms are rearranged and new bonds form
Chemical equation- used to represent a chemical reaction
Reactants- substances present before a reaction
Products- substances present after a reaction

12. Example

13. Steps for Writing Chemical Equations
Ex. Hydrogen gas reacts with oxygen gas to produce liquid water
Identify reactants and products
Ex. Reactants: hydrogen and oxygen
Products: water

14. Steps for Writing Chemical Equations
Write the chemical formulas
Watch for the seven diatomic elements
Remember the three “common names” we discussed
Elements in their natural state have no charge
Do NOT carry subscripts from one side of the equation to the other side. Each formula is what it is due to the “zeroing” out of its ionic charges or its appropriate molecular formula.
Ex. Reactants: H2 and O2
Products: H2O

15. Steps for Writing Chemical Equations
Write reactants on the left (order does not matter), followed by an arrow pointing to the products on the right (order does not matter).
Ex. H2 + O2 → H2O

16. Steps for Writing Chemical Equations
Add the physical state symbols next to each substance (you will do this ONLY in lab after this chapter)(one symbol per substance)
(s) = solid
(l) = liquid
(g) = gas
(aq) = aqueous solution (means dissolved in water)
Ex. H2 (g) + O2 (g) → H2O (l)

17. Another Example
Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor.
Identify reactants and products
Reactants: Methane gas and oxygen gas
Products: carbon dioxide gas and water vapor

18. Another Example
Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor.
Write the chemical formulas
Reactants: CH4 + O2
Products: CO2 + H2O

19. Another Example
Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor.
Write reactants on the left, followed by an arrow pointing to the products on the right
CH O2  CO H2O

20. Another Example
Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor.
Add the physical state symbols next to each substance
CH4(g) O2(g)  CO2(g) H2O(g)

21. Law of Conservation of Matter
Law of Conservation of Mass/Matter- in a chemical reaction, atoms are neither created nor destroyed
Must be the same number of atoms of each element on the product side as on the reactant side 

22. Practice
Example: Potassium metal dissolves in liquid water to form hydrogen gas and aqueous potassium hydroxide. Reactants: K + H2O Products: H2 + KOH K(s) + H2O(l)  H2(g) + KOH(aq)

23. Practice
Example: Aqueous potassium iodide and aqueous lead (II) nitrate reacts to form aqueous potassium nitrate and a precipitate of lead (II) iodide.
Reactants: KI + Pb(NO3)2
Products: KNO PbI2
KI(aq) + Pb(NO3)2(aq)  KNO3(aq) + PbI2(s)
1-2A

24. DO NOW:
Solid zinc is added to aqueous hydrochloric acid which produces hydrogen gas and zinc chloride that remains dissolved in the water. Write the equation, balance it and indicate the phases.
Zn(s) HCl(aq)  H2(g) + ZnCl2(aq)

25. Writing Chemical Equations- cont’d
The Law of Conservation of Matter states that the number of atoms of each element must be the same on the reactant and product side. Therefore, we have to balance the equation.
Balance the equation
Never change the chemical formula (including subscripts)
If you need more atoms of an element, you can add more of the substance containing that element (sometimes it’s balanced as is).

26. Balance the equation
Hydrogen gas reacts with oxygen gas to produce liquid water
H2 + O2 → H2O
(We worked with this equation yesterday)
2 H; 2 O H; 1 O
Oxygen atoms are not balanced!

27. Balance the equation
If we add another water, that will give us two oxygen atoms on the product side. However, the number of hydrogen atoms will also change.
H2 + O2 → H2O + H2O
2 H; 2 O 4 H; 2 O
Hydrogen atoms are not balanced!

28. Balance the equation
If we add another hydrogen gas, the number of hydrogen atoms will be equal on both sides of the equation.
H2 + H2 + O2 → H2O + H2O Everything is balanced!
4 H; 2 O H; 2 O

29. Balance the equation
Writing chemical formulas multiple times is tedious. Therefore, we use a coefficient (a whole number placed in front of a formula) to indicate how many molecules of a substance is needed.
Balance the equation by using a coefficient to indicate the number of each molecule. Use the lowest whole number possible (make sure to double-check the entire equation).
2H2 (g) + O2 (g) → 2H2O (l)

30. Practice Writing and Balancing Chemical Equations
Methane gas reacts with oxygen gas to produce carbon dioxide gas and water vapor
CH O2 → CO H2O
Balance the equation by using a coefficient to indicate the number of each molecule.
CH4(g) O2(g)  CO2(g) H2O(g)

31. Helpful Hints
“Skeleton Equation” - an equation that has the reactant and product formulas already written for you.
Sometimes you will be given an equation where Steps 1-3 are already done for you. This makes your life a little easier.

32. Helpful Hints Sometimes the physical states will also be given to you.
It is probably easier to omit the physical states as you try to balance the equations. Your paper will be too cluttered and it will be hard to recognize the proper coefficients.
If needed (usually for word problems and lab problems) you can add the physical states back into the balanced equation when you’re finished.   

33. Example
Solid zinc is added to aqueous hydrochloric acid which produces hydrogen gas and zinc (II) chloride that remains dissolved in the water.
Zn HCl → H ZnCl2
Balance the equation by using a coefficient to indicate the number of each molecule.
Zn(s) HCl(aq)  H2(g) + ZnCl2(aq)

34. Another Example
HELPFUL HINT: If the problem has an atom that is even on one side and odd on the other side, double what is “odd” to help you balance the equation.
Ammonia gas reacts with oxygen gas to yield nitrogen monoxide gas and gaseous water
4 NH3(g) O2(g) → 4 NO(g) H2O(g)

35. DO NOW
Write the skeleton (unbalanced) equation for the following reaction  
HINT: zinc is a transition metal that always has a +2 charge so we do not write “zinc (II)”.
Solid zinc is added to aqueous nitric acid (HNO3) which produces hydrogen gas and zinc nitrate that remains dissolved in the water.
Zn(s) + HNO3(aq)  H2(g) + Zn(NO3)2(aq)

36. Writing Chemical Equations
When polyatomic ions are involved, balancing an equation can be a little trickier.
Let’s look at some polyatomic ions and correctly written compounds containing polyatomic ions and count how many atoms of each element are represented.
Or… count how many polyatomics there are if they do not change during the reacion.

37. Example
Ex. (from “DO NOW”) Solid zinc is added to aqueous nitric acid (HNO3) which produces hydrogen gas and zinc nitrate that remains dissolved in the water
Before we balance the equation, let’s look at the zinc nitrate product and count how many atoms of each element are represented.
Zn(s) + HNO3(aq)  H2(g) + Zn(NO3)2(aq)

38. Example Never change the chemical formula (including subscripts)
If you need more atoms of a element, you can add more of the substance containing that element
Zn HNO → H Zn(NO3)2
1 Zn H; 1N; 3 O H Zn; 2 N; 6 O
Hydrogen atoms are not balanced!
Nitrogen atoms are not balanced!
Oxygen atoms are not balanced!

39. Example
If we add another molecule of nitric acid, that will give us twice as many atoms of H and N and O. This will balance the equation.
Zn HNO HNO3 → H Zn(NO3)2
1 Zn H; 1N; 3 O 1H; 1N; 3 O H Zn; 2 N; 6 O
You should learn to write this with a coefficient.
Zn (s) HNO3 (aq) → H2 (g) + Zn(NO3)2 (aq)
1 Zn H; 2N; 6 O H Zn; 2 N; 6 O balanced!!

40. Example
Ex: Aqueous potassium iodide and aqueous lead (II) nitrate reacts to form aqueous potassium nitrate and a precipitate of lead (II) iodide.
Reactants: KI + Pb(NO3)2
Products: KNO3 + PbI2
2 KI (aq) Pb(NO3)2 (aq)  2 KNO3 (aq) PbI2 (s)

41. REMINDER:
If the problem has an atom that is even on one side and odd on the other side, double what is odd to help you balance the equation. 

42. Now you try a problem like that described above from start to finish:
Ex: Liquid ethanol (C2H5OH) reacts with oxygen gas to form carbon dioxide and water vapor.
Answer: C2H5OH(l) O2(g)  2CO2 (g) H2O(g)

44. DO NOW:
Solid zinc is added to aqueous hydrochloric acid which produces hydrogen gas and zinc chloride that remains dissolved in the water. Write the equation, balance it and indicate the phases.
Zn(s) HCl(aq)  H2(g) + ZnCl2(aq)

45. Shall We Dance? POGIL
Synthesis: element or less complex compounds come together to form a single more complex compound
Decomposition: a compound breaks apart into either elements or less complex compounds
Single Replacement: a single element replaces another one in a compound
Double Replacement: ions in a compound switch places with ions in another compound to form two new compounds

47. Classifying Reactions
Directions: Predict the products and then balance the following equations. You do not need to include the physical states.
Synthesis (direct combination or composition)- a compound is formed from simpler substances
Ex. 2Na + Cl2 → 2NaCl
A + B  AB

48. Classifying Reactions
Decomposition- a compound is broken down into simpler substances Ex. 2H2O → 2H2 + O2 AB  A + B

49. Classifying Reactions
Single replacement (displacement)- cations or anions are exchanged Ex. Mg + CuSO4 → MgSO4 + Cu (Mg and Cu+2 switch) (metal replaces a metal) A + BC  AC + B SHOULD - Need to check the reactivity series for metals to see if a single metal replacement reaction occurs.

51. Classifying Reactions
Double replacement reaction- reaction in which cations and anions are exchanged (like replaces like)
Ex. CaCO3 + 2HCl → CaCl2 + H2CO3
AB + CD  AD + CB

52. Classifying Reactions
Combustion- a rapid reaction involving oxygen that produces heat (flame)
Hint: Sometimes these are difficult to balance!
Ex. CH4 + 2O2 → CO2 + 2H2O
(products are always the same)
  CxHx + O2 → CO2 + H2O
CH4 is a hydrocarbon – a compound containing hydrogen and carbon

53. HINTS: Combustion Reactions often need two hints:
Again, if the problem has an atom that is even on one side and odd on the other side, double what is odd to help you balance the equation.
We have seen that often our coefficients are “2”s and “3”s. Since combustion often takes a LOT of oxygen to occur, the coefficients are often large numbers!

54. Classifying Reactions
Acid/Base Neutralization Reaction:  is a chemical reaction in which an acid and a base react with each other. Usually produces water and a salt.
Hint: Sometimes these are difficult to balance!
Ex. KOH + HCl → KCl + H2O
(Salt – any ironically bound material)
Mg(OH)2 + 2HNO3 → Mg(NO3)2 + 2H2O

55. ____ NaBr + ____ H3PO4  ____ Na3PO4 + ____ HBr Type of reaction: ____________________ ____ Ca(OH)2 + ____ Al2(SO4)3  ____ CaSO4 + ____ Al(OH)3 ____ Mg + ____ Fe2O3  ____ Fe + ____ MgO

56. Ethene gas (C2H4) is burned in oxygen gas to produce carbon dioxide gas and water vapor.

57. Solid lead(II) sulfate is heated to produce solid lead(II)sulfite and oxygen gas.

58. Liquid water is added to gaseous sulfur trioxide to produce aqueous sulfuric acid.

59. Aqueous sulfuric acid is added to solid ammonium hydroxide to produce liquid water and aqueous ammonium sulfate.

60. ____ NaBr + ____ Ca(OH)2  ___ CaBr2 + ____ NaOH Reaction Type : ______________ ____ NH3+ ____ H2SO4  ____ (NH4)2SO4 ____ C5H9O + ____ O2  ____ CO2 + ____ H2O

61. Solid lead is mixed with aqueous phosphoric acid (H3PO4) to produce hydrogen gas and aqueous lead (II) phosphate.

62. Solid lithium nitride is added to aqueous ammonium nitrate to produce aqueous lithium nitrate and aqueous ammonium nitride.

63. Aqueous hydrochloric acid is mixed with solid aluminum hydroxide to produce liquid water and aqueous aluminum bromide.