1. UNIT 1 Matter Day 34 October 17, 2017
Law of Conservation of Mass
8th Grade Science

2. 6th Period – come in and sit down.

3. Turn in your homework. (“Find the Image”)
Pick up a copy of the Lab – Law of Conservation of Mass/Matter.
Take out your “Messing with Mixtures” station lab sheet and wait for directions.
Take out your notes on Law of Conservation of Mass.

4. Plan for today:
Inquiry Lab on the Law of Conservation of Mass
Lesson on Law of Conservation of Mass- balancing chemical equations:
*notes/discussion
*video
*practice

5. Homework:
Finish the lab sheet.

6. E.Q. –What is the Law of Conservation of Matter/Mass?

7. Inquiry lab - “law of conservation of mass/matter”
This is a lab that is easy to mess up if you do not read and follow the directions very carefully.
Therefore, we will do each step of this lab TOGETHER.
DO NOT get ahead of me.

8. Take out your notes called “Law of Conservation of Mass” and let’s fill in some information.

9. Law of Conservation of matter (Mass)
Def. This law states that matter (mass/atoms) CANNOT be created or destroyed in ordinary physical or chemical changes.
A.D. The total mass of the reactants equals the total mass of the products.
A.D. This can be proven in a closed system… one in which nothing enters or leaves the system.
10g
20g
30g

10. Conservation of Mass in a closed system

11. Was the chemical reaction you observed today inside a closed system or was it an open system?

12. Law of Conservation of Mass
Def. This law states that ______________ CANNOT be _____________ or _____________ in ordinary ______________or ________________ ________________.
The total __________________________________________
______________________________________________________.
This can be proven in a __________ ___________…one in which nothing enters or leaves the system.

13. Let’s look at the Law of Conservation of Mass and Chemical Equations presented Brainpop’s way.
Brainpop - Law of Conservation of Matter

14. Now let’s learn how to balance chemical equations.
A Quick Review
elements
Chemical symbols represent __________.
compounds
Chemical formulas represent __________.
Chemical equations represent __________.
chemical reactions.
Now let’s learn how to balance chemical equations.

15. Now let’s learn how to balance chemical equations.
A Quick Review
Chemical symbols represent __________.
Chemical formulas represent __________.
Chemical equations represent __________.
Now let’s learn how to balance chemical equations.

16. In a chemical reaction, no atoms are gained or lost
In a chemical reaction, no atoms are gained or lost. They just get rearranged.
Because this Law of Conservation of Matter (Mass) has been proven, chemical equations (which represent a chemical reaction) MUST be balanced (same number of atoms on both sides).
mass of the reactants=mass of the products.

17. *Coefficient: a number that is placed in front of a chemical symbol or formula in order to balance a chemical equation. Subscripts (the little numbers) CANNOT be changed to balance an equation. Why?
H2O 2H20 -2 molecules of water
CO2 4CO2 – 4 molecules of carbon dioxide
C6H12O6

18. *Coefficient: a number that is placed ____________ a chemical _________ or _________ in order to __________ a chemical ___________. Subscripts __________ be _________ to balance an equation. Why?
H2O 2H20 -2 molecules of water
CO2 4CO2 – 4 molecules of carbon dioxide
C6H12O6

19. More O2 in the reactants.
Count to be sure the number of atoms of each element is the same in the reactants and products.

20. How to Balance Chemical Equations: 3 Simple Steps
Step 1: Count the number of atoms for each element on both sides of the equation. Look for elements that are not balanced.
Ex. Mg O2 MgO
Mg- Mg-
O- O-
_____ is unbalanced.

21. Step 2: Add a coefficient in front of the formula that contains the unbalanced element(s). The O was unbalanced. Place a coefficient 2 in front of the MgO. ***Note: This may throw off the balance of other elements, so you have to keep working with it.
Ex. Mg O2 __ MgO
This will balance the O, but unbalance the Mg. So…add another coefficient 2 in front of the Mg in the reactant.
Ex. ___Mg O2 2 MgO
*This should balance the Mg but be sure to do Step 3.

22. Step 3: Check the number of atoms on both sides of the equation to be certain they are balanced.
2Mg O 2MgO
Mg- Mg-
O- O-
Is it balanced? If so, you have supported the Law of Conservation of Matter (Mass).

23. How does balancing equations illustrate and support the Law of Conservation of Mass/Matter?
*Because they require that you have the same mass after the reaction as you do before the reaction. This means…
*The # and type of atoms are the same in the reactants and products (just in different combinations)
*Although the state of matter of the products may be different from the reactants, the overall mass doesn’t change.

24. Let’s look at Chemical Equations presented Brainpop’s way.
Brainpop-Chemical Equations

25. Let’s practice balancing some chemical equations
Let’s practice balancing some chemical equations. “Balancing Act” practice sheet.
Use pencil. You may have to change coefficients a few times.

26. Wrap-up:
Any questions?