Unit 5: Chemical Reactions
Law of Conservation of Mass
Name _______________________________________________
Date ________________ Period _______ Assignment 2
Notes
Law of Conservation of Mass
 In other words…__________________________________________________________!
BrainPOP
1. In science, a law is:
A. A rule governing what you are permitted to do
B. A generalization about how the physical universe
works
C. A legal document that describes a rule of conduct
D. A statute enacted by a legislative body
6. When sodium and chlorine combine to form sodium
chloride, sodium chloride is the:
A. Originator
B. Reactant
C. Product
D. Produce
2. What is true of a substance with a lot of mass?
A. It contains a lot of matter
B. It has a large volume
C. It has a high density
D. It has a low frequency
7. 4 grams of hydrogen and 32 grams of oxygen will
combine to form:
A. 36 grams of water
B. 28 grams of hydroxide
C. 32 grams of oxygen
D. 36 grams of deuterium
3. The law of conservation of mass says substances
can neither ____ nor ____.
A. Built; torn down
B. Blended together; separated
C. Created; destroyed
D. Condensed; extracted
4. How is weight different from mass?
A. Weight changes depending on gravity; mass
stays constant
B. Weight is measured in grams’ mass is measured
in newtons
C. Weight can be converted to energy; mass cannot
D. Weight is measured with a scale; mass is
measured with a triple-beam balance
5. Sodium and chlorine combine to form sodium
chloride, or table salt. Sodium and chlorine are:
A. Producers
B. Products
C. Reactionaries
D. Reactants
8. In a chemical reaction, 4 grams of sodium must
combine with how many grams of chlorine to produce
10 grams of table salt?
A. 4 grams
B. 6 grams
C. 8 grams
D. 10 grams
9. What was Antoine Lavoisier’s contribution
to the law of conservation of mass?
A. He was the first person to think of it
B. He was the first person to propose it in a
scientific way
C. He came up with a widely-read, precise
description
D. He was the first person to perform a chemical
reaction
10. Which of the following describes a chemical reaction?
A. Oxygen interacts with iron to form rust
B. Ice melts into water
C. Carbon dioxide freezes to make dry ice
D. Rocks split apart over many years due to
weathering
Investigation
Introduction:
The Law of Conservation of Mass states that matter (can / cannot) be created nor destroyed; it can only be transformed from state to
state. The chemical formulas that we will investigate are below. Circle the reactants and underline the products.
Sodium Bicarbonate + Acetic Acid → Sodium Acetate + Carbon Dioxide + Water
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
Question:
__________________________________________________________________________________________________
__________________________________________________________________________________________________
Materials:




Vinegar
2 plastic cups


Baking soda
Dropper
Scale
Plastic bag
Procedure:
 1. Pour the cup of baking soda into the plastic bag.
 2. Put 5 full droppers of vinegar in the second cup.
 3. Place the cup with vinegar in the plastic bag without spilling the vinegar.
 4. Seal the plastic bag completely.
 5. Record the mass of the bag with the reactants (baking soda & vinegar) and cup inside.
 6. Without opening the bag, pour the vinegar out of the cup.
 7. Without opening the bag, record the mass with the products (______________ & ______________) and cup inside.
Observations:
Reactants
1.
(solid / liquid / gas)
2.
Data:
Initial Mass (g)
Products
(solid / liquid / gas)
Final Mass (g)
1.
2.
Change in Mass (g)
[Final Mass – Initial Mass]
Graph:
Instructions: Create a bar graph to show the initial, final, and
in the investigation.
(solid / liquid / gas)
(solid / liquid / gas)
Graph Checklist
 # increments on the x-axis
 Label on the x-axis
 Units on the x-axis
 # increments on the y-axis
 Label on the y-axis
change
observed
 Unitsinonmass
the y-axis
 Title describing the data
Conclusions:
Instructions: Use at least 1 complete sentence to answer the questions below.
1. Describe what happened when the vinegar was poured into the baking soda.
2. Was this a chemical reaction? What evidence do you have to support your answer?
3. How does the mass of the product compare to the mass of the reactant after the chemical reaction occurred?
4. Why was it important to observe this investigation in a completely closed plastic bag?