Today’s Agenda

1. Today’s Agenda • (1) Expressing chemical reactions • (2)Balancing chemical reactions • (3) Chapter 5 work section 3 and 4 • **Test on Thursday: you can use your notes

2. Warm Up • What is the difference between naming Covalent compounds and Ionic compounds?

3. Naming Ionic Compound • Write the full name of the cation and use the root of the anion with “ide”. • Naming Covalent Compound • Use the full name of the more metallic • Followed by the root of the less metallic • Add “ide” to the root • Use the numeric prefixes to show how many

4. Expressing Chemical Reactions

5. I. Review • Remember that a chemical reaction is a reaction between two or more substances that causes chemical bonds to break and then be reformed as new products are formed. • A sign that a chemical reaction has taken place is heat, light, bubbling, burning, smoke and vapor, or an explosion.

6. I. Review C. If a new molecule or molecules have formed after a reaction, then it was a chemical reaction.

7. I. Review D. A chemical reaction is indicated by an arrow. On the left side of the arrow are the things that go into a chemical reaction and react together, called reactants. And on the right side of the arrow are the things that are produced, called products. Reactants Products

8. Chemical equation - uses chemical formulas and symbols to describe a chemical reaction and the product it produces (see below)

9. II. Reactants and Products • So reactants react together, have a chemical reaction, and products are produced. • The reactants are the substances that change and the products are the substances formed.

10. II. Reactants and Products C. Some examples of chemical reactions: Methane + Oxygen Carbon Dioxide + Water CH4 + O2 CO2 + H2O Reactants Products

11. II. Reactants and Products Iron + Oxygen Iron(III) Oxide Fe + O Fe3O2 Reactants Products

12. III. Law of Conservation of Mass • In the 1700’s, chemical reactions were still a bit of a mystery. A French scientist, Antoine Lavoisier, established an important principle based on his experiments with chemical reactions. • He stated that the total mass of the of the products of a reaction is equal to the total mass of the reactants.

13. III. Law of Conservation of Mass C. The law of conservation of mass states that the total mass of the products equals the total mass of the reactants. D. That means, for example, if you perform a chemical reaction and burn something, the mass of what ever you are burning will equal the mass of the ashes and the gas given off by the reaction.

14. Coefficients • #’s which represents the number of units of each substance in a rxn 4Al (s) + 3O2 (g)2Al2O3 Subscripts • #’s which represent the number of atoms in a molecule of a particular element

15. III. Law of Conservation of Mass E. Because conservation of mass takes place in a chemical equation, it is necessary to balance a chemical equation to show this.

16. Balancing Chemical Equations

17. I. Review A. Remember that a chemical reaction is indicated by an arrow, and that the reactants are on the left and the products are on the right. Reactants Products

18. I. Review B. The Law of Conservation of Mass states that the total mass of the products of a reaction is equal to the total mass of the reactants. C. Because conservation of mass takes place in a chemical reaction, it is necessary to balance a chemical equation to show conservation of mass.

19. II. Numbers in Chemical Equations • There are two types of numbers in chemical equations, and they mean two different things. • The two different types of numbers are 1. Subscript numbers 2. Coefficient numbers

20. II. Numbers in Chemical Equations C. A subscript number is used to show the number of atoms in a compound. When we wrote compounds correctly, we used subscript numbers. • H2O - The 2 is the subscript number • NH3 - The 3 is the subscript number • Li2SO4 - The 2 and 4 are subscript numbers

21. II. Numbers in Chemical Equations G. Subscript numbers are used to correctly write individual molecules. H. Coefficient numbers are used to correctly balance chemical equations. I. Coefficient numbers are big numbers to the LEFT of an atom or molecule that indicate how many atoms or molecules are needed to balance an equation.

22. II. Numbers in Chemical Equations J. 3H2O - The 3 is the coefficient number K. 4NH3 - The 4 is the coefficient number L. 2 NaCl – The 2 is the coefficient number

23. III. Balancing Chemical Equations A. The key to balancing equations is to make sure that you have the same number of each atom on the left and the right side of a chemical equation.

24. III. Balancing Chemical Equations B. The three steps to balancing chemical equations are as follows: • Write your chemical equation • Check and see how many atoms of each element are on each side of the equation • Write coefficients in front of any atoms or molecules to make the equation balanced.

25. III. Balancing Chemical Equations Practice 1. CH4 + O2 CO2 + H2O 2. C: 1 C: 1 H: 4 H: 2 O : 2 O: 1 3. To balance the equation, you need 2 more H’s and 1 more O on the left side. Add a coefficient 2 in front of the H2O CH4 + O2 CO2 + 2H2O

26. III. Balancing Chemical Equations • HCl + CaCO3 CaCl2 + CO2 +H2O • H: 1 H:2 Cl: 1 Cl:2 Ca: 1 Ca:1 C: 1 C:1 O: 3 O:3 3. Add a 2 coefficient in front of the HCl 2HCl + CaCO3 CaCl2 + CO2 + H2O

27. Quiz • Please take out a sheet of paper • Number from 1-10 • You can use your notes • Please turn your quiz over when you are done • You can listen to music or rest after quiz

28. 10 Minutes

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30. 6 Minutes

31. 5 Minutes

32. 4 Minutes

33. 3 Minutes

34. 2 Minutes

35. 1 Minute Left

36. 30 Seconds

37. Please pass your quiz answer sheet to the front • Make sure your name is on it