Is this a Physical or a Chemical Reaction?
Materials for Each Group
 1 Clear plastic soda or water bottle
 50 mL of vinegar
 1 Graduated cylinder
 1 Medium balloon



1 Funnel
2 Teaspoons of baking soda
Balance
Procedures
 Measure 50 ml of vinegar with a graduated cylinder.
 Measure the mass of a plastic bottle using a balance. Record in Table 1.
 Pour the 50 ml of vinegar into the plastic bottle. Calculate the mass of the plastic bottle
plus the vinegar. Then, use the balance to find the actual mass. Record in Table 1.
 Using the information in Table 1, calculate the mass of the vinegar by subtracting the
mass of the bottle from the bottle and vinegar together.
 Measure the mass of an empty balloon. Record in Table 2.
 Using the funnel, carefully pour 2 teaspoons of baking soda into the balloon.
 Predict the mass of the balloon plus baking soda. Then use the balance to find the actual
mass. Record in Table 2.
 Using the information in Table 2, calculate the mass of the baking soda by subtracting the
mass of the balloon from the mass of the balloon with baking soda.
Table 1: Bottle Data
Material
Mass
Plastic bottle
_________g
Plastic bottle with vinegar
_________g
Vinegar
_________g
Table 2: Balloon Data
Material
Mass
Balloon
_________g
Balloon with baking soda
_________g
Baking soda
_________g
 Twist the balloon to keep the baking soda inside the top of the balloon.
 Without spilling any of the baking soda, stretch the mouth of the balloon over the mouth
of the bottle.
 Looking at tables 1 and 2, calculate the total mass of your set-up (bottle + vinegar +
balloon + baking soda). Record in Table 3.
 Verify calculation by measuring the mass of your set-up with a balance. Record in Table
3.
 Have one person hold the bottle as another turns the balloon completely upright, so that
the baking soda inside the balloon pours into the bottle with the vinegar. Observe what
happens and record your observations below:
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Is this a Physical or a Chemical Reaction?
Draw your Set-Up before adding baking soda
Picture should have a deflated balloon
attached to the bottle.
Draw your Set-Up after adding baking soda
Picture should have an inflated balloon
attached to the bottle.
1. What two substances combined in the experiment? _____________________________
The vinegar and baking soda combined._______________________________________
2. Did the baking soda and vinegar make a reaction? How do you know?
Yes, the bubbles and the inflated the balloon are evidence of a chemical reaction.______
_______________________________________________________________________
_______________________________________________________________________
3. Did the reaction form a new solid, liquid, or gas? Explain.
Students should note the formation of gas. They may also report seeing the formation___
of a new solid and a new liquid.______________________________________________
_______________________________________________________________________
4. Did the temperature of the bottle change? Explain.
Students should feel that the bottle feels cooler during the reaction__________________
_______________________________________________________________________
_______________________________________________________________________
5. What evidence is there that a chemical reaction has taken place? __________________
Bubbles indicate that a gas was formed causing the balloon to expand._____________
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Is this a Physical or a Chemical Reaction?
The cooler temperature of the bottle is another indication that a chemical reaction has__
Taken place.___________________________________________________________
 Carefully place the bottle (with the balloon still attached) on the balance. Record this
mass in Table 3.
Table 3: Data of Set-Up
Mass of Set-Up Before
(calculated)
Plastic bottle + Balloon
____________ g
Vinegar + Baking Soda
____________ g
Total
____________ g
Mass of Set-Up After
(measured)
____________ g
6. Compare the total mass of your Set-Up before and after. What do you observe and what
can you explain? _________________________________________________________
Answers will vary but the mass of the products should be approximately the same as___
the mass of the reactants.__________________________________________________
_______________________________________________________________________
_______________________________________________________________________
7. Explain how this experiment shows that the mass of an object is equal to the sum of all
its parts.
The masses of reactants and products should be the same._______________________
_______________________________________________________________________
_______________________________________________________________________
8. Give two reasons why the mass of the reactants in your experiment may not be exactly
equal to the mass of the products.
Answers may include: human error, spilled some of the baking soda, did not read______
balance correctly, balloon was not on tightly so some of the gas escaped.____________
_______________________________________________________________________
_______________________________________________________________________
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Is this a Physical or a Chemical Reaction?
Teacher Notes:
During the exercise, make sure to ask probing questions and find out what students understand
from the process. This experiment is not designed to solve a problem statement, but to use the
Nature of Science process to make observations, gather data, and reflect on the information
collected.
In a chemical reaction, the substances that you start with (the reactants) are different from the
substances you finish with (the products). In this activity, the reactants were the baking soda (a
pure substance) and vinegar (a solution). The products were a mixture of water, carbon dioxide,
and a kind of salt called sodium acetate. Also, you have learned that the sum of the reactants
(the Set-Up Before) was equal to (almost) the sum of the products (the Set-Up After). Some of
the reasons why the two might not have been exactly equal are that (1) some of the carbon
dioxide escaped, (2) the pan balance was not completely accurate, and (3) human error during
the measuring of mass of the substances occurred.
Examples that a chemical reaction is taking place are (1) color change, (2) formation of a gas,
(3) formation of a solid, and (4) changes in temperature as a result of energy exchange.
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