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Conservation of Mass
Rachael Hart
6th period
December 8, 2011
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Introduction
If a chemical reaction takes place, then the law of the conservation of mass applies. The
Law of Conservation of Mass explains that mass can neither be created nor destroyed in a normal
chemical reaction. Although different reactants may change from one state of matter to another
their mass remains the same because of this law. As long as the different reactants are kept
sealed in a container, their mass will remain the same in any normal chemical reaction. This is
true because a reactant may appear lighter when in a liquid form, but the container would
probably be filled with gases, which also hold some mass when sealed up into a container.
Materials and Methods
Materials and Equipment:

Laboratory balance

Erlenmeyer flask

Rubber stopper (for flask)

Graduated cylinder

Test tubes

Corks (to fit test tubes)

Labels

Safety goggles

Lab apron or coat

Sodium Carbonate (Na CO )

Calcium Chloride (CaCl )

Sulfuric Acid (H SO )
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Safety Precautions
When experimenting in the lab and especially when working with acids remember to
wear goggles. When handling acids also remember to wear a lab apron or coat. In this
experiment dilute the solution with water when cleaning the equipment and disposing the
solution.
Procedures
1.) Measure 10 mL of sodium carbonate (Na CO ) solution in a graduated cylinder. Pour the
solution into an Erlenmeyer flask that is both dry and clean and then put a stopper into the flask.
Clean the graduated cylinder.
2.) In the graduated cylinder, measure 3 mL of 1 M calcium chloride (CaCl ) solution and pour
the solution into a clean and dry test tube. Label and cork the test tube. Rinse out and dry the
graduated cylinder.
3.) Use the graduated cylinder to measure 3 mL of sulfuric acid (H SO ) solution and pour the
solution into a clean, dry test tube. Then cork and label the tube. Clean out the graduated
cylinder. Caution: Handle this acid carefully.
4.) Place the test tubes and the flask on a laboratory balance in a way that the equipment is
stable. Make sure the solutions do not touch the corks. Measure the total mass of the containers,
stoppers, and solutions. This will be mass a in the data table.
5.) Take the flask filled with the sodium carbonate solution and the test tube containing calcium
chloride solution off the laboratory balance. Pour the calcium chloride solution into the sodium
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carbonate solution, swirl the flask to thoroughly mix the two solutions together. Record any
observations.
6.) Put the cork and the stopper back in their containers. Measure the total mass of the stoppers,
the containers, and their contents. Record this as mass b in the data table.
7.) Remove the test tube with the sulfuric acid solution and the flask from the laboratory balance.
Carefully pour the sulfuric acid solution into the flask. Swirl the flask WITH THE STOPPER
OFF until all bubbling ceases. Record any observations and give the flask time to cool down to
room temperature.
8.) Place the stopper and the cork back on their original containers. Measure the mass of the
stoppers, containers, and the contents again. Record this number as mass c in the data table.
Data and Results
Mass
Mass (grams)
a
363.46g
b
363.44g
c
363.36g
This table shows the mass of the stoppers, the three containers, and their contents throughout this
experiment measured in grams. Mass a shows the mass before any reactions occur. Mass b is
the mass after mixing the sodium carbonate solution with the calcium chloride solution, and
mass c is the mass after mixing the sulfuric acid solution with the contents in the flask.
In order to find the mass of the contents alone, the mass of the equipment, which is the
flask, the test tubes, and the stoppers, being worked with must be measured when empty. Then
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to know the mass of the contents themselves subtract the mass of the equipment from the total
mass.
Sample calculation: 363.46g – 348.96g = 14.5g
363.46g is mass a; 348.96g is the mass of the equipment; 14.5g is the difference of the two and
is, therefore, the mass of the contents
Discussion
The experiment features aqueous solutions of three different compounds that react
together chemically. The reactions make physical changes apparent. The purpose of this
experiment is to show and provide a better understanding of the Law of Conservation of Mass.
The Law of Conservation of Mass states that in a normal chemical reaction mass is
neither created nor destroyed. Antoine Lavoisier, a French chemist, established this law. The
measurements taken during this experiment should prove out the Law of Conservation of Mass.
In this experiment, different solutions were enclosed in separate containers and then
mixed together. Once the materials are in order, the first step was taken in the mixing process.
The calcium chloride solution was poured into the sodium carbonate solution, swirled, and then
enclosed again with a cork or some kind of stopper. The next chemical reaction that occurred
was when the sulfuric acid solution was mixed to the other solution, swirled, and sealed up
again.
Color changes, temperature changes, a change in smell, and bubbling are some
indications that a chemical reaction is occurring. In the first chemical reaction that took place
the calcium chloride solution started to become thicker and whiter in color when mixed with the
sodium carbonate solution. The two solutions mixed together formed a precipitate, which is
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when a solid forms from a chemical reaction. When a pair of soluble reactants in a solution are
mixed together, the presence of a solid at the bottom shows that a reaction has taken place.
Sometimes cloudy solutions appear because the precipitate particles are too small to settle out.
When a precipitate is formed, a change of state may be all that is apparent, but the chemical
structure of the substance has most likely changed as well. Solid pieces started to appear in the
foggy solution. The second chemical reaction bubbled initially and caused the solution to
become more like a liquid again.
Measurements must be taken throughout the experiment. The measurements should
prove that no matter the state of the solutions their mass remains the same throughout the
ordinary chemical reactions. The measurements should consistently remain the same throughout
the experiment, which models the Law of Conservation of Mass. The measurements taken when
this experiment was conducted were off by tenths and some by hundredths of a gram. This still
proves the Law of Conservation of Mass while also accounting for some possible human errors.
Conclusion
The results of this experiment prove the Law of Conservation of Mass. In this
experiment, solutions were mixed and new ones were formed. The different solutions underwent
a couple of chemical reactions, but the mass of the solutions remained nearly the same. The part
of the procedure that would need improvement would be the part the person conducting the
experiment is accountable for doing. Pouring out the correct amount of each solution and putting
on the stoppers quickly enough are two ways that human error could play a part. This
experiment was able to prove that mass cannot be created nor destroyed in a normal chemical
reaction, which is what the Law of Conservation of Mass states.
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References
The Law of Conservation of Mass. Retrieved December 14, 2011. From
http://www.mi.mun.ca/users/edurnfor/1100/atomic%20structure/tsld004.htm.
Senese, Fred (February 15, 2010). Ten Signs of Chemical Change. Retrieved December 20,
2011. From http://antoine.frostburg.edu/chem/senese/101/reactions/symptoms.shtml.
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