The document discusses chemical reactions, including identifying reactants and products, applying the law of conservation of matter stating the mass of reactants equals the mass of products, and recognizing that chemical reactions can form gases or precipitates. Reactants in the example reaction are S2O3 and I2, and products are S4O6 and 2I. If reactants are 12g, products are also 12g, and if reactants mass is more, a gas was likely formed. A precipitate is a solid that forms in a solution.

1. 1/31/12 A/B Day
LEQ: What can happen to the reactants in a
chemical reaction?
1. What is the difference between a natural material
and a synthetic one?
2. Is steel natural or synthetic?
3. Is neon natural or synthetic?
4. A scientist is looking for evidence of a chemical
change. What is one thing he should look for?
5. A scientist is looking for evidence of a physical
change. What is one thing she should look for?

2. EOG Question:
Which of the following may happen during a
physical change?
A. New substances are formed
B. Reactants form products
C. A precipitate is formed
D. The temperature may increase

3. Let’s Review:
LAW OF CONSERVATION OF MATTER
Matter can’t be
_________ and it
can’t be
_____________.

4. Today’s LEQ: What can happen to the
reactants in a chemical reaction?
By the end of today, you should be able to…
1. Identify reactants and products
2. Apply the law of conservation of matter to
chemical reactions
3. Identify the creation of gases and precipitates
as a part of a chemical reaction

5. How many words can you make
using ONLY the letters below?
A A S P M E N R
U W T T G O B P

6. A A S P M E N R
U W T T G O B P
• Past • Brat
• West • Want
• Aspen • Poem
• Tram • Rap
• Pan • Part
• We • Sap
• Sat • Spent
• Men • Grant

7. Elements are
like
letters, compo
unds are like

8. FOCUS VOCABULARY:
90. Chemical Reaction
91. Reactant
92. Product
93. Precipitate

9. Elements are like
letters, compounds are like
words.
A CLOSER LOOK AT
CHEMICAL CHANGES!

10. Element + Element Compound
+
Two One Water
Hydrogen Oxygen
Atoms Atom

11. Compounds
Explain subscript numbers

12. DRAW THIS IN YOUR NOTES:
Chemical Reaction: process of forming
new substances (a chemical change!)
2H + O H 2O H O2

13. 2H + O H2O
+
Two One Water
Hydrogen Oxygen
Atoms Atom

14. DRAW THIS IN YOUR NOTES:
Chemical Reaction: process of forming
new substances (a chemical change!)
2H + O H 2O H O 2
1 Oxygen
2 Hydrogens 1 Water

15. EOG QUESTION:
Carbon combines with oxygen to form carbon
dioxide. What is the word equation for this
chemical reaction?
a. carbon dioxide carbon + oxygen
b. carbon  carbon dioxide + oxygen
c. carbon + oxygen  carbon dioxide
d. carbon dioxide + oxygen  carbon

16. DRAW THIS IN YOUR NOTES:
Chemical Reaction: process of forming
new substances (a chemical change!)
Reactants Product
2H + O H 2O H O 2
1 Oxygen
2 Hydrogens 1 Water

17. Big Numbers vs. Little Numbers
H2O 6 H2O
ONE WATER 6 WATER
MOLECULE MOLECULES
-12 hydrogens,
-2 hydrogens
-6 oxygens
-1 oxygen

18. Big Numbers vs. Little Numbers
Reactants Products
6 CO2 + 6 H2O C6H12O6 + 6 O2
6 Carbon 6 Waters 1 Glucose 6 Oxygen
Dioxides particles

19. BrainPop: Chemical Equations

20. In your notes…
1. Reactants:
Products:
2. Reactants:
Products:
3. Reactants:
Products:
4. Reactants:
Products:

21. 1. 2 H₂0₂  2 H₂0 + O ₂
2. C3H8 + 5 O2  4 H2O + 3 CO2
3. 4 Al + 3 O2  2 Al2O3
4. 6 CO₂ + 6 H₂OC₆H₁₂O₆ + 6 O₂

22. Chemical Reactions
Law of Conservation of Matter

23. Law of Conservation of Matter
Mass of reactants ALWAYS
EQUALS the mass of the products!
Example:
Reactants = 12 g
Products = 12 g

24. 2H + O H2O
+
Two One Water
Hydrogen Oxygen
Atoms Atom

25. REACTANTS = PRODUCTS
Reactants Products
6 CO2 + 6 H2O C6H12O6 + 6 O2
6 Carbons 6 Carbons
12 Hydrogens 12 Hydrogens
18 Oxygens 18 Oxygens

26. EOG QUESTION:
If the mass of the reactants in a chemical
reaction is 123.49 grams, what is the mass
of the products?
a. 78.49 grams
b. 123.49 grams
c. 246.98 grams
d. impossible to tell

27. 1. 2 H₂0 ₂  2 H ₂ 0 + O ₂
12 g  _____?_____
2. C3H8 + 5 O2  4 H2O + 3 CO2
4 .5 g + 3.5 g  _______?_______
3. 4 Al + 3 O2  2 Al2O3
10 g + _?_  18 g
4. 6 CO₂ + 6 H₂OC₆H₁₂O₆ + 6 O₂
75g + 45 g  10g + __?__

28. EOG QUESTION:
Chemical X has a mass of 5 grams, and chemical Y has
a mass of 10 grams. If the two chemicals are mixed
and a complete chemical reaction takes place, what is
most likely the mass of the product?
a. 5 grams
b. 10 grams
c. 15 grams
d. 50 grams

29. How is this possible with the law of
conservation of matter?
Reactants Products

30. DEMO: Let’s watch a
chemical reaction!

31. Reactants Products

32. Chemical Reactions
Law of Conservation of Matter
Mass of reactants -chemical
ALWAYS EQUALS reactions
the mass of the can
products! sometimes
Ex: form a
Reactants = 12 g
GAS!
Products = 12 g

33. EOG QUESTION:
After a chemical reaction occurs in an open test
tube, measurements indicate that the mass of the
reactants is greater than the mass of the products
remaining in the test tube. What most likely explains
the measurements?
a. a gas was produced
b. a solid was produced
c. the salinity of the reactants was high
d. the temperature of the reactants was low

34. What in the world is a precipitate?
• http://www.youtube.com/watc
h?v=RE-
dFN7U91M&feature=related
• http://www.youtube.com/watc
h?v=pFovlKpPCbI
• http://www.youtube.com/watc
h?v=Trdyqmzu3JA&feature=rel
ated

35. Chemical Reactions
Law of Conservation of Matter
Mass of reactants -chemical -chemical
ALWAYS EQUALS reactions reactions
the mass of the can can also
products! sometimes form a
Ex: form a PRECIPITATE!
Reactants = 12 g
GAS! (a solid that
Products = 12 g forms in a
solution)

36. Let’s Practice!

37. Summarizer:
Consider the following: 2 S2O3 + I2 → S4O6 + 2I
1.What are the reactants?
2.What are the products?
3.If there are 12 grams of reactants in a chemical
reaction, what is the mass of the products?
4.If you create a chemical reaction in an open test
tube and the mass of the reactants is MORE than
the mass of the products, what happened?!
5.What is a precipitate?