Conservation of Mass in Chemical Reactions Lab
5th Grade PSI Science
Name: __________________
Score: ______________ / 5
Experiment Question:
What happens to the total mass of substances when a chemical reaction occurs?
Hypothesis Starters:
1. Define the term “Conservation of Mass.”
2. Define the term “chemical reaction.”
3. What are some common signs of chemical reactions?
Purpose:
In this experiment, you will explore what happens to the total mass of a solution
when a chemical reaction occurs. During a chemical reaction, starting chemicals come
into contact to form products with different physical properties. They may have a
different color or may change from a liquid to a solid. One technique chemists often use
to help substances react is to dissolve them in water first. This allows the pieces to
move around and react more easily.
Even though new substances are made, Conservation of Mass is still true.
Sometimes this is tricky to show like when you burn a match or a candle. Some of the
products are gases like carbon dioxide which often just float away and mix with the air.
These gases have mass which counts but since they float away, they do not get
measured. This makes Conservation of Mass seem like it isn’t true. Any time it looks
like Conservation of Mass is not true, look at your reaction and try to figure out where
the extra mass came from or where it went.
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Matter and Its Interactions
Safety
Flames will be used during this activity. Never hold a burning object with your
hands. Always use tongs or place it in a fire-safe dish and let it burn there. Goggles and
aprons should be worn at all times.
Materials
The materials and directions for each station are included individually. Complete
each station before moving on to the next station. There are extra station spaces at the
end for you to write in stations that you have created or that your teacher has created
for you in addition to the standard stations.
Station One: Magnesium Ribbon
Materials:
Ceramic dish
2.5cm long piece of magnesium ribbon
Wand style lighter
balance or scale
Directions:
1. Record the starting mass of the ceramic dish and the
magnesium ribbon.
2. Record observations of the magnesium ribbon in its original
state.
3. Ignite the magnesium ribbon with the lighter.
4. DO NOT look directly at the magnesium ribbon while it burns
because it may damage your eyes.
5. Record observations of the magnesium ribbon after it has
reacted.
6. Once the ceramic dish cools to room temperature, record the
ending mass of the ceramic dish and the burned magnesium.
7. Clean up as instructed by your teacher.
Observations Starting Mass
Ending Mass
Starting Observations
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Ending Observations
Matter and Its Interactions
Station Two: Vinegar and Baking Soda Version 1
Materials:
Balance or Scale
Scrap Paper
Vinegar
Baking soda
50mL or 100mL Graduated Cylinder
Directions:
1. Place the scrap paper on the balance.
2. Add about 1.0g of baking soda to the scrap paper
3. Add about 25.0mL of vinegar to the graduated cylinder
4. Place the graduated cylinder on the balance with the scrap
paper and baking soda.
5. Record the starting mass of everything on the balance.
6. Record starting observations of everything on the balance.
7. Pour the baking soda into the graduated cylinder slowly so that it
does not foam over the top.
8. Record observations of what happened during the reaction and
what the chemicals look like after the reaction has stopped.
9. Place the scrap paper on top of the graduated cylinder.
10. Record the ending mass of everything on the balance.
11. Clean up as instructed by your teacher.
Observations Starting Mass
Ending Mass
Starting Observations
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Ending Observations
Matter and Its Interactions
Station Three: Vinegar and Baking Soda Version 2
Materials:
Balance or Scale
Balloon, log and skinny like for balloon
animals
Rubber band
Vinegar
Baking soda
10mL Graduated Cylinder
Directions:
1. Place the empty balloon on the balance.
2. Add about 0.25g of baking soda to the balloon.
3. Shake all of the baking soda to the bottom of the balloon.
4. About 1.0cm above the baking soda in the balloon, twist the
balloon 10 times to close off the baking soda from the rest of the
balloon.
5. Fold the end of the balloon up and use the rubber band to make
sure it does not accidentally unfold.
6. Add about 5.0mL of vinegar to the graduated cylinder
7. Add the vinegar to the balloon and carefully tie the end of the
balloon closed.
8. Place the balloon with the rubber band on the balance.
9. Record the starting mass of everything on the balance.
10. Undo the rubber band.
11. Untwist the balloon so the vinegar and baking soda can react.
12. Once the reaction stops, place the balloon and rubber band on
the balance.
13. Record the ending mass of everything on the balance.
14. Record observations of the reaction.
15. Place the graduated cylinder on the balance with the scrap
paper and baking soda.
16. Record the starting mass of everything on the balance.
17. Record starting observations of everything on the balance.
18. Pour the baking soda into the graduated cylinder slowly so that it
does not foam over the top.
19. Record observations of what happened during the reaction and
what the chemicals look like after the reaction has stopped.
20. Clean up as instructed by your teacher.
Observations Starting Mass
Ending Mass
Starting Observations
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Ending Observations
Matter and Its Interactions
Station Four: Copper (II) Nitrate with Sodium Hydroxide
Balance or Scale
2 Beakers
Test tube with Copper (II) Nitrate solution
Test tube with Sodium Hydroxide solution
Directions:
1. Place one test tube in each beaker so they do not tip over or roll
away.
2. Place everything on the balance.
3. Record the starting mass of everything.
4. Record observations of everything.
5. Take the beakers off of the balance.
6. Take the copper (II) nitrate test tube out of its beaker.
7. Pour the copper (II) nitrate solution into the empty beaker.
8. Place the empty test tube in the other beaker.
9. Pour the sodium hydroxide into the beaker with the copper (II)
nitrate.
10. Place the empty test tube with the other test tube in the beaker.
11. Record observations of what happened when the solutions were
mixed.
12. Place both beakers and their contents on the balance.
13. Record the ending mass of everything.
14. Clean up as instructed by your teacher.
Observations Mass Before
Mass After
Materials:
Observations Before
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Observations After
Matter and Its Interactions
Custom Station
Materials:
Directions:
Observations
Before:
Observations
During:
Observations
After:
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Laboratory Questions:
On a sheet of paper or in your laboratory notebook, answer the following questions for
each station you were able to test.
1. Was conservation of mass true at station one? Explain your thinking.
2. Was conservation of mass true at station two? Explain your thinking.
3. Was conservation of mass true at station three? Explain your thinking.
4. Was conservation of mass true at station four? Explain your thinking.
5. What purpose did the balloon serve at station three? Did it collect anything?
Conclusion:
On a sheet of paper or in your laboratory notebook, write a paragraph or two that
summarizes the experiment results and covers the following key points.
1. How did you know that chemical reactions occurred at each station?
2. Was Conservation of Mass true at each station? If not, why not?
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Matter and Its Interactions
Notes to the Teacher:
Be aware of your school’s policy regarding latex balloons. Some schools do not permit
their use because of latex allergies. Often, you may be granted permission if you
perform it as a demonstration.
This could be set up as a station experiment where the students perform each station or
as a demonstration experiment where the teacher performs each for the class as a
whole. You don’t technically need to do all four stations. One station should illustrate the
point if performed correctly.
Station one can be easily done as a demo if fire safety is a concern. The extra mass
comes from the oxygen in the air. This experiment disproves the idea of “phlogiston.” If
your students are not familiar with phlogiston, you may wish to have them complete a
quick research of it to show how scientific ideas are refined and corrected throughout
history.
Be sure to test the amounts listed in station three to make sure your balloons will not
overinflate and pop. Adjust amounts if needed.
Station four should have color changes and a precipitate that forms.
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5th Grade PSI
Matter and Its Interactions