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RRHS Science 10 Chemistry Slide #1 What is a Chemical Reaction? Two atoms can be mixed together to create a new compound (sodium & chlorine) Can also mix.

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Presentation on theme: "RRHS Science 10 Chemistry Slide #1 What is a Chemical Reaction? Two atoms can be mixed together to create a new compound (sodium & chlorine) Can also mix."— Presentation transcript:

1 RRHS Science 10 Chemistry Slide #1 What is a Chemical Reaction? Two atoms can be mixed together to create a new compound (sodium & chlorine) Can also mix two compounds to create new compounds (baking soda & vinegar) New substances are produced in each case with properties different from the original substances.

2 RRHS Science 10 Chemistry Slide #2 Dalton’s Atomic Theory All matter is made up of small particles called atoms Atoms cannot be created, destroyed, or divided into smaller particles All atoms of the same element are identical in mass and size, but different in mass and size from atoms of other elements John Dalton

3 RRHS Science 10 Chemistry Slide #3 Conservation of Mass Law of conservation of mass states: –The total mass of the reacting substances (the reactants) is always equal to the total mass of the resulting substances (the products). Matter is neither created or destroyed in a chemical reaction. Atoms in the reactants are present in the products.

4 RRHS Science 10 Chemistry Slide #4 Writing Chemical Equations Lets look at how water is formed. First we can look at the word equation. Hydrogen + Oxygen  Water Reactants on the left side of the arrow Products on the right side of the arrow Plus sign means “reacts with” Arrow means “produce”

5 RRHS Science 10 Chemistry Slide #5 The Hindenburg Zeppelin Video on File Hydrogen + Oxygen  Water

6 RRHS Science 10 Chemistry Slide #6 Atoms can share electrons with the same atom. These molecules have two of the same atoms joined by a covalent bond. Since there are two of the same atoms the word diatomic is used. (“di” meaning two) Seven elements are diatomic: Hydrogen - H 2 Chlorine - Cl 2 Oxygen - O 2 Bromine - Br 2 Nitrogen - N 2 Iodine - I 2 Fluorine - F 2

7 RRHS Science 10 Chemistry Slide #7 Skeleton Equations For water the skeleton equation is: H 2 + O 2  H 2 O According to Conservation of Mass the reactants and products must have the same number of atoms. We must balance the chemical equation. This is done by adding coefficients in front of the compounds.

8 RRHS Science 10 Chemistry Slide #8 Balancing the Reaction Important: Subscripts CANNOT be changed!!!!!! Hydrogen is balanced so you must balance the oxygen by adding another water molecule H 2 + O 2  2H 2 O Now hydrogen is not balanced so we must add another hydrogen molecule 2H 2 + O 2  2H 2 O

9 RRHS Science 10 Chemistry Slide #9 Check The Atoms Add up all the atoms of both reactants and products to make sure the amounts are the same. Reactants 2 H 2 Molecules 4 H atoms 1 O 2 Molecule 2 O atoms Products 2 H 2 O molecules 4 H atoms 2 O atoms 2H 2 + O 2  2H 2 O

10 RRHS Science 10 Chemistry Slide #10 Tips for Balancing 1.Adjust co-efficients, not chemical formulas (subscripts). 2.Balance metals first 3.Add co-efficients to individual elements last 4.If a polyatomic ion appears in in both reactant and product, treat it as a single unit. 5.Balance oxygen and hydrogen last. 6.Don’t forget diatomic molecules. 7.Count your atoms as a check

11 RRHS Science 10 Chemistry Slide #11 Let’s Try Some Together Mg + O 2  MgO AgI + Na 2 S  Ag 2 S + NaI NaOH + H 2 SO 4  Na 2 SO 4 + H 2 O CaCl 2 + Na 3 PO 4  Ca 3 (PO 4 ) 2 + NaCl FeS + O 2  Fe 2 O 3 + SO 2

12 RRHS Science 10 Chemistry Slide #12 Your Turn 1. H 2 + O 2  H 2 O 2. S 8 + O 2  SO 3 3. HgO  Hg + O 2 4. Zn + HCl  ZnCl 2 + H 2 5. Na + H 2 O  NaOH + H 2

13 RRHS Science 10 Chemistry Slide #13 Chemical States The state of the chemicals is important to the chemical reaction. State can be added by putting an abbreviation in parentheses after each chemical. StateAbbreviationExample Solid(s)NaCl(s) Liquid (l)(l)H 2 O( l ) Gas(g)H 2 (g), O 2 (g) Aqueous(aq)NaCl(aq) (in water)

14 RRHS Science 10 Chemistry Slide #14 Water: Final Balanced Equation Hydrogen and Oxygen are both gases Water is a liquid Final balanced equation with the states of all components is: 2H 2 (g) + O 2 (g)  2H 2 O( l ) You will not be required to give the states for an equation

15 RRHS Science 10 Chemistry Slide #15 Resources - Links Khan Academy Balancing Equations pHET Balancing Applet Balancing Complex Equations with the Table Method VideoBalancing Complex Equations with the Table Method Video

16 RRHS Science 10 Chemistry Slide #16 Resources – Table Example Step 1: Start with an unbalanced equation

17 RRHS Science 10 Chemistry Slide #17 Resources – Table Example Step 2: Draw boxes around all the chemical formulas

18 RRHS Science 10 Chemistry Slide #18 Resources – Table Example Before = Reactant After = Product Step 3: Make an element inventory

19 RRHS Science 10 Chemistry Slide #19 Resources – Table Example Before = Reactant After = Product Step 4a: Balance the Equation and the Inventory

20 RRHS Science 10 Chemistry Slide #20 Resources – Table Example Before = Reactant After = Product Step 4b: Final Steps…

21 RRHS Science 10 Chemistry Slide #21 Resources – Extra Practice The following are Word Based Balancing Problems Page 137: Q14 Page139: Q22, Q23, Q26

22 RRHS Science 10 Chemistry Slide #22 Answers - Let’s Try Some Together 2Mg + O 2  2MgO 2AgI + Na 2 S  Ag 2 S + 2NaI 2NaOH + H 2 SO 4  Na 2 SO 4 + 2H 2 O 3CaCl 2 + 2Na 3 PO 4  Ca 3 (PO 4 ) 2 + 6NaCl 4FeS + 7O 2  2Fe 2 O 3 + 4SO 2

23 RRHS Science 10 Chemistry Slide #23 Answers - Your Turn 1. 2H 2 + O 2  2H 2 O 2. S O 2  8SO HgO  2Hg + O 2 4. Zn + 2HCl  ZnCl 2 + H Na + 2H 2 O  2NaOH + H 2


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