1. Notes Tennessee SPI Objective: Recognize that in a chemical reaction the mass of the reactants is equal to the mass of the products (Law of Conservation of Mass) Science SPI 0807.9.11 Law of Conservation of Mass  No atoms are created or destroyed during chemical reactions So no mass is created or destroyed Instructions 1) First click on "View" from the top-menu bar. 2) Then click on "Slide Show" from the drop-down menu. 3) Then use the right-arrow button on your keyboard to advance through this presentation.

2. 2 parts of chemical equations Reactants: chemicals you start with in a reaction Products: chemicals you end up with in a reaction Example: 2H 2 + O 2 2H 2 O SPI 0807.9.11 Law of Conservation of Mass Reactants (Hydrogen & Oxygen) Product (water) (1) reactants (2) products Notes Science

3. 3 key symbols in chemical equations Subscript: small number below & to the right of a chemical symbol  reveals the number of atoms Coefficient: big number in front of a chemical symbol or formula  (tells you to multiply) Yields Arrow: always points towards the products Example: 2H 2 + O 2 2H 2 O (1) Subscript (2) Coefficient (3) Yields Arrow SPI 0807.9.11 Law of Conservation of Mass Notes Science

4. H 2 + O 2 H 2 O  Atoms are never created or destroyed in a chemical reaction … they are just rearranged. 2 & 1 2 & 2 Four is not equal to three! SPI 0807.9.11 Law of Conservation of Mass Notes Science …Law of Conservation of Mass All chemical reactions always obey the… Wrong Example: Look at the unbalanced equation shown below. Notice that it is written incorrectly. Therefore it is impossible for this reaction to occur like this. (count the atoms on each side of the equation) It DOES NOT obey this law.

5. Balancing Equations: Note: You will learn about this in more detail in High School. 2H 2 + O 2 2H 2 O Notes SPI 0807.9.11 Law of Conservation of Mass 4 & 2 Six is equal to Six! This demonstrates the law of conservation of mass. Science Example: Here is the same equation from the previous slide, but now I have balanced it by placing coefficients Task: Make the amount of reactants equal the amount of products. We use coefficients to do this. (count the atoms on each side of the equation)

6. Na + Cl 2 2NaCl How many sodium (Na) reactants? How many sodium (Na) products? How many chlorine (Cl) reactants? How many chlorine (Cl) products? Does this demonstrate the law of conservation of mass? Two Quick Review Two No it does not! SPI 0807.9.11 Law of Conservation of Mass (count the atoms on each side) One Why? Look at the sodium atoms on each side

7. 2N 2 + O 2 2N 2 O How many nitrogen (N) reactants? How many nitrogen (N) products? How many oxygen (O) reactants? How many oxygen (O) products? Does this demonstrate the law of conservation of mass? Four Quick Review Two Yes it does! SPI 0807.9.11 Law of Conservation of Mass (count the atoms on each side) Four Why? Same number of atoms on each side

8. Here is a question you might see on a quiz or test. Questions Science Sample: SPI 0807.9.11 Law of Conservation of Mass Hint: Count the atoms on each side of the arrow

9. Here is a question you might see on a quiz or test. Questions Science Sample: SPI 0807.9.11 Law of Conservation of Mass Hint: Count the atoms on each side of the arrow

10. Here is a question you might see on a quiz or test. Questions Science Sample: SPI 0807.9.11 Law of Conservation of Mass Hint: Count the amounts of reactants and products

11. Here is a question you might see on a quiz or test. Questions Science Sample: SPI 0807.9.11 Law of Conservation of Mass Hint: Use substitution: K= 39 grams, O= 32 grams …so 39 + 32 ???

12. Here is a question you might see on a quiz or test. Questions Science Sample: SPI 0807.9.11 Law of Conservation of Mass Hint: Count the amounts of reactants and products.