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: LOCOM) Science Check for Understanding Model how to count the numbers of atoms on each side of chemical reactions to confirm the Law of Conservation of Mass. Essential Question(s) How do I determine the number and type of atoms on each side of a chemical equation to confirm the LOCOM? SPI 0807.9.11 Law of Conservation of Mass Instructions for Students 1) Make sure you view this presentation in slideshow mode. 2) You can find instructions about how to do this by doing a Google search or by searching YouTube. 3) After you have it in slideshow mode, press the right-arrow keyboard button to advance through the presentation. 4) If you need help, please communicate with your teacher.

2. 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: LOCOM) 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 LOCOM

3. 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 2 parts of chemical equations

4. Subscript: small number below & to the right of a chem 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 3 key symbols in chemical equations

5. 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! …Law of Conservation of Mass All chemical reactions always obey the… Wrong Example: Look at the unbalanced equation shown below. 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.

6. F.Y.I. Balancing Equations: Note: You will learn about this in more detail in High School. 2H 2 + O 2 2H 2 O 4 & 2 Six is equal to Six! Now it demonstrates the law of conservation of mass. Example: Here is the same equation from the previous slide, but now I have balanced it by placing coefficients. You 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)

7. 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 Science

8. 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 it 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 Science

9. SPI 0807.9.11 Law of Conservation of Mass Hint: Count the atoms on each side of the arrow Review

10. Science SPI 0807.9.11 Law of Conservation of Mass Hint: Count the atoms on each side of the arrow Review

11. Science SPI 0807.9.11 Law of Conservation of Mass Hint: Count the amounts of reactants and products Review

12. Science SPI 0807.9.11 Law of Conservation of Mass Hint: Use substitution: K= 39 grams, O= 32 grams …so 39 + 32 ??? Review

13. Science SPI 0807.9.11 Law of Conservation of Mass Hint: Count the amounts of reactants and products.