Law of Conservation of Mass Lab
Purpose:
To discover and write the meaning of the Law of Conservation of Mass by observing
the masses before and after a physical change and chemical change.
Hypothesis:
How do you think mass of paper will change after tearing it? How do you think
the mass of baking soda and vinegar will change after they react without a balloon covering the
reaction? How do you think the mass will change if you cover the reaction with a balloon?
Materials:
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balance
Water Bottle
1 balloon
sheets of paper
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funnel
graduated cylinder
baking soda
vinegar
Introduction:
The word equation for the following reaction is as follows:
vinegar + baking soda ==> sodium acetate + water + carbon dioxide
The chemical equation for the reaction is:
CH3COOH + NaHCO3
==> NaC2H3O2
+ H2O + CO2
Procedure:
Physical Change – Trial 1 Tearing Paper
1. Record the mass of a folded piece of paper on the scale in the table below.
2. Tear the paper into small pieces. Do not lose any pieces. Place them on the scale and
record the mass of the torn paper in the table below.
Chemical Change – Reaction of vinegar and baking soda Trial 1
1. Record the mass of the empty water bottle in the table below. Pour about 25 mL of
vinegar into the water bottle. Record the mass of the water bottle & vinegar in the table
below.
2. Record the Weight of a piece of paper in the table below. Add ~3 g extra of baking soda
onto the piece of paper. Record the exact mass of baking soda and paper used in the table
below.
3. Place the water/vinegar over a sink. Add the baking soda to the bottle. Record the mass
after the baking soda and vinegar have reacted fully as the total mass after reaction.
4. Rinse out the bottle thoroughly
Chemical Change – Reaction of vinegar and baking soda Trial 2
1-2. Complete the same steps as trial 1.
3. Place the water/vinegar on the scale. Add the baking soda to the inside of the balloon.
Attach the balloon to the bottle top and then pour the baking soda in. Hold the balloon to
the top tight. Record the mass after the baking soda and vinegar have reacted fully as the
total mass after reaction.
4. Rinse out the bottle thoroughly.
Figure 1
Figure 2
Figure 3
Data:
Table 1: Physical Change Trial 1 Paper Mass Folded vs Torn
Object
Calculations
Paper Folded
N/A
Paper Torn
N/A
Mass
Table 2: Chemical Change Trial 1 Before and After without Balloon
Object
Calculations
Water Bottle
N/A
Water Bottle + Vinegar
N/A
Vinegar Only
(Mass of Water Bottle + Vinegar) – Water bottle
Mass
Paper
N/A
Paper & Baking Soda
N/A
Baking Soda
(Mass of Paper & Baking Soda) – (Mass of Paper)
Total Mass After Reaction
N/A
Mass of Reactants Before
(Mass of Vinegar) + (Mass of Baking Soda)
Reaction (Initial Mass)
Mass of Products after
(Total Mass of Scale After Reaction) – (Mass of
Reaction (Final Mass)
Water Bottle)
Mass
Table 3: Chemical Change Trial 2 Before and After with Balloon
Object
Calculations
Water Bottle
N/A
Water Bottle + Vinegar
N/A
Vinegar Only
(Mass of Water Bottle + Vinegar) – Water bottle
Mass
Paper
N/A
Paper & Baking Soda
N/A
Baking Soda
(Mass of Paper & Baking Soda) – (Mass of Paper)
Total Mass After Reaction
N/A
Mass of Reactants Before
(Mass of Vinegar) + (Mass of Baking Soda)
Reaction (Initial Mass)
Mass of Products after
(Total Mass of Scale) – (Mass of Water Bottle)
Reaction (Final Mass)
Calculations
Calculate the (1) Change in Mass and (2) Percent Change in Mass for
Equation 1: 𝑪𝒉𝒂𝒏𝒈𝒆 𝒊𝒏 𝑴𝒂𝒔𝒔 = 𝑰𝒏𝒊𝒕𝒊𝒂𝒍 𝑴𝒂𝒔𝒔 − 𝑭𝒊𝒏𝒂𝒍 𝑴𝒂𝒔𝒔
Equation 2: 𝑷𝒆𝒓𝒄𝒆𝒏𝒕 % 𝑪𝒉𝒂𝒏𝒈𝒆 𝒊𝒏 𝑴𝒂𝒔𝒔 =
Physical Change….
Change in Mass
Percent Change in Mass
Chemical Change Trial 1 …
Change in Mass
Percent Change in Mass
Chemical Change Trial 2 …
Change in Mass
Percent Change in Mass
𝑰𝒏𝒊𝒕𝒊𝒂𝒍 𝑴𝒂𝒔𝒔−𝑭𝒊𝒏𝒂𝒍 𝑴𝒂𝒔𝒔
𝑰𝒏𝒊𝒕𝒊𝒂𝒍 𝑴𝒂𝒔𝒔
Mass
Inquiry/Analysis Questions (Refer to Your Notes for this Week for some of the questions):
1. Why was tearing paper a physical change? Why was reacting baking soda and vinegar a chemical change? Explain the difference
between a chemical change and physical change. What evidence was there that a chemical change occurred?
2. What state of matter was present for the paper? What states of matter were the vinegar and baking soda before the reaction?
What states of matter were present after the reaction? What was the purpose of the balloon in trial 2 of the chemical change?
3. How did the final mass after the physical change compare with the initial mass of the system(what was the change in mass and
the % change in mass)? How did the final mass after the chemical change in trial 1 compare with the initial mass of the system
(what was the change in mass and the % change in mass)? How did the final mass after the chemical change in trial 2 compare
with the initial mass of the system(what was the change in mass and the % change in mass)?
4. Was there is a difference between the change in mass chemical change trial 1(without the balloon) vs trial 2(with the balloon)?
If so, why was there a difference? The Law of the Conservation of Mass states what happens to the mass of matter during
physical and chemical changes. Based on what you observed, what happens to the mass of matter during changes?
Conclusion: Based on the difference of mass before and after the physical change and the chemical change, what can you
conclude about changes in mass due to physical and chemical changes? Write a single statement below.