1. Law of Conservation of Mass
SWBAT: Apply the law of conservation of mass to chemical equations.
When is the law of conservation of mass true?
What happens to the mass of substances when they undergo a chemical reaction?

2. SWBAT: Apply the law of conservation of mass to chemical equations.
Why it matters in LIFE: The application of laws and theories is a skill that you will use for the rest of your life. It is important to not only understand laws but be able to apply them.
Why it matters in THIS CLASS: This law will help you understand how to represent chemical equations accurately.

3. Chemistry in a bag:
E.Q. How do we know that a chemical reaction occurred?
Chemistry in a bag -
If I were to put my reactants and products on the balance or scale, how much would they weigh?
Copy the next two slides on to your note sheet in the column next to the arrow.

4. Law of Conservation of Mass
WHAT GOES IN MUST COME OUT!!!!!
Matter can neither be created nor destroyed
in a chemical reaction.

5. In other words
The  (Yields or produces) Separates the reactants from the products
EVERYTHING ON THE LEFT OF THE ARROW IS A REACTANT
EVERYTHING ON THE RIGHT OF THE ARROW IS A PRODUCT
The mass of the reactants ( ALWAYS) must equal the mass of the products ( Substance a reaction ends with)

6. Law of Conservation of Mass

7. Think back to the demo
If I left the balloon off the flask would mass have been conserved…
YESSSSS! I just would not have had the ability to measure it!

8. Big hints about chemical equations
Coefficient
State of matter (s) (l) (g) (aq)
Subscript

9. Open vs. Closed Systems
Open System: reaction taking place in an open system can exchange matter with its surroundings. We, therefore, have no way to measure the matter.
Closed System: reaction taking place in a closed system cannot exchange matter with its surroundings, and we can measure the matter.

10. How do we represent the law within a chemical equation?
MAKE SURE THE NUMBER OF PRODUCTS IS EQUAL TO THE NUMBER OF REACTANTS NaCl + H2O  NaOH + Cl2 Balanced not balanced HCl + NaOH NaCl+ H2O Balanced not balanced N2 + O2  N2O Balanced Not Balanced H2 + O  H2O Balanced Not Balanced

12. Guided practice Think pair share
Rolando is doing an experiment he mixes hydrochloric acid with aluminum in an open test tube. Before the reaction he takes the mass of the system it has a mass of 12g. The reaction produces hydrogen gas. Rolando weighs the system after the reaction it now has a mass of 8g. Explain why the reaction system does not have the same mass before and after the reaction.