Teacher’s Instructions:
Chemically Inflating a Balloon
Recommended grade levels: 2-6, estimated time 30-40 minutes
Summary:
In this adaptation of a common household science experiment the combination of
baking soda and vinegar are put to new uses to demonstrate states of matter, density, and
conservation of matter within a closed system. Students will conduct four experiments in
two parts. Part 1 focuses on the states of matter of the reactants and products. Through
the use of a balance part 2 demonstrates conservation of matter while incorporating
density and the beginnings of dimensional analysis to compare the expected versus the
experimental final mass.
Teaching Objectives:
 Communication: students will communicate effectively in the applications of science
and technology.
 Scientific reasoning: students will learn to formulate and justify ideas and to make
informed decisions.
 Inquiry and problem solving: Students will apply inquiry and problem-solving
approaches in science and technology by observing and collecting data from their
own experimental design
 Structure of Matter: Students will understand the structure of matter and the
changes it undergoes
 Describe how physical properties of objects change during chemical reactions.
 Explain how matter changes in both chemical and physical ways
Concept Background:
Conservation of matter: in a closed system, matter cannot be created nor destroyed,
it can only change states. For this experiment the sealed plastic bag serves to keep the
system closed to all outside forces. Since the system is closed the initial mass should be the
same as the final mass.
States of matter: the three most common types of matter, and the ones we are
concerned with for this experiment, are solid, liquid, and gas. Solids have a definite shape
and volume. Liquids have a distinct volume but conform to the shape of their container.
Gases have neither a definite shape nor volume; they will expand to fill their containers and
are compressible given enough pressure.
Density is a physical characteristic of a substance defined as the mass of the
substance divided by its volume. Density is most commonly expressed as grams per liter.
For this experiment the density of two liquids are given and students are asked to calculate
the mass of their sample given the density and volume. It is meant a s a simple
multiplication exercise, but it can lead to the greatest experimental error if the students
have not carefully measured 50mL of their liquids.
Materials List:
Who’s Polluting the River?, Ben Bricker, Colby College, January 2012
Acetic Acid
White vinegar is available at most grocery stores with
the condiments.
Alka-seltzer tablets Available at most drug stores in the pharmacy.
Baking Soda
Available at most grocery stores in the baking isle.
Small cups
Dixie cups from a grocery store work well, but any
vessel that freely stands upright that can keep the
alka-seltzer/baking soda from the liquid will work.
Plastic bags
Small sealable plastic bags from the grocery store,
commonly sold as lunch bags.
Weighing balance Scientific weighing balances with a precision of at least
.00 are necessary to demonstrate conservation of
matter.
Graduated Cylinder Available from most scientific supply stores. Can be
substituted with a common cooking measuring cup.
Safety Notice:
All materials listed are safe to flush down the drain at the end of lab.
Excess baking soda and vinegar in too small of a plastic bag may cause the bag to tear,
loudly. In 15 trials three plastic lunch bags tore, but no reactants were forcibly expelled.
Students should still be warned before hand of the possibility of loud bursting.
Experimental Setup:
Lab groups of 2 or 3 work best. Set each group up with four plastic bags, two alkaseltzer tablets (one package), a graduated cylinder (or substituted measuring device), four
plastic cups, and enough worksheets for each student (student worksheets attached). Set
out beakers or large containers with water and vinegar for students to draw from. Two
250mL beakers for each water and vinegar was adequate for a class of 21. Have the
balance also set up with baking soda next to it at the front of the room. Total prep time: 15
minutes for seven lab groups.
Beginning the Experiment:
Instructors should begin by reviewing states of matter with the class. Make sure
students can accurately identify solids, liquids, and gasses as well as explain what makes
them different. Instructors can walk through the first part of the experiment, or simply
explain where the necessary materials have been laid out and encourage students to
practice following a step-by-step written procedure. Students will begin by predicting
which of the four reactions will produce the most gas. After predicting they need to collect
50mL of water, bring it back to their group, and work together to introduce the liquid,
plastic cup, and alka-seltzer tablet to a plastic bag without mixing the reactants. Once the
bag has been sealed students may invert or shake the bag vigorously to begin the reaction.
Have students label this bag once the reaction has consumed the tablet, set to the side, and
move on to the next reaction in which water is replaced by vinegar. It is important that
students remember to still record the state of matter for reactants and products for
reaction two. Frequently students will get very excited to attempt the next gas-producing,
plastic bag-inflating reaction and skip the recording step. A mild reminder usually serves
to refocus even hyperactive groups. For part two students will be using a balance or scale
to collect measurements for the plastic cup and proper amount of baking soda. 3.25g of
Who’s Polluting the River?, Ben Bricker, Colby College, January 2012
baking soda is recommended for reactions three and four to most closely approximate the
mass of a single alka-seltzer tablet. Reaction three, baking soda and water, usually helps to
calm groups after reactions one and two due to the limited reaction of water and baking
soda. Before reaction four students will once again need to use the balance to collect
measurements for their plastic cup and baking soda amount. Reaction four produces the
most gas, and is the most likely to pop a poorly sealed, or weakened plastic bag. If the bag
does pop, it usually pops above the level of the vinegar, so as long as the bag is kept upright,
or placed within another container, spills are easily avoided. After the excitement of
reaction four students move on to a small multiplication exercise where density is
introduced and an example problem serves to illustrate how the mass of a specific volume
of liquid may be determined from its density (volume*density=mass). If students’
experimental values differ greatly (+/- 5 grams) from the expected value having students
theorize on sources of experimental error can be a useful exercise.
References:
Brown, Theodore, Lemay Eugene and Bruce Bursten. Chemistry the Central Science 9th
Edition. Upper Saddle River : Pearson Education, 2003.
Millard, Jullie. "CH151: k-8 Chem Outreach." January 2012. Colby College Department of
Chemistry Course Web Pages. January 2012
<http://www.colby.edu/chemistry/CH151_current/CH151_current.html>.
US Department of Energy. Newton Archives. April 2011. January 2012
<http://www.newton.dep.anl.gov/>.
Name:
Date:
Who’s Polluting the River?, Ben Bricker, Colby College, January 2012
Chemical Inflation
Student Handout
Introduction:
Today you will be investigating important chemical concepts such as the states of
matter, density, and the conservation of matter. Working in groups of three you will
investigate four chemical reactions. These reactions will be conducted within a sealed
plastic bag so that you may see how much gas is produced by each reaction.
Procedure:
Part 1. States of Matter
1. Predict. Which reaction do you believe will produce the most gas? (circle one)
Baking Soda + Water
Alka-Seltzer + Water
Baking Soda + Vinegar
Alka-Seltzer + Vinegar
2. Record. Send one group member to the front table with your graduated cylinder to
collect 50mL of water and 2 Alka-Seltzer tablets. Record the states of matter for
each reactant.
Alka-Seltzer tablets:
Solid
Liquid
Gas
Water:
Solid
Liquid
Gas
3. Experiment. Put the Alka-Seltzer tablet in one of the small cups.
Pour the 50mL of water into a plastic bag.
Put the plastic cup in the bag, but do not let the cup fall.
Seal the bag. Make sure it is airtight.
Shake the bag so that the Alka-Seltzer tablet is exposed to the water
What state of mater is the product of Alka-Seltzer added to water?
Product:
Solid
Liquid
Gas
4. Repeat. Send another group members up to the front table to get 50mL of vinegar.
Repeat step 3 with the vinegar. Record the states of matter for each reactant and
the product.
Alka-Seltzer tablets:
Solid
Liquid
Gas
Vinegar:
Solid
Liquid
Gas
Product:
Solid
Liquid
Gas
Part 2. Conservation of Matter
1. Send two group members to the front; one to collect 50mL of water, the other with a cup
to measure out 3.25g of baking soda.
Who’s Polluting the River?, Ben Bricker, Colby College, January 2012
2. Record the mass of the cup first.
a. Mass of cup:
3. Weigh out roughly 3.25g of baking soda into the cup. Record the final mass.
b. Mass of cup + baking soda:
4. Return to your desk and pour the 50mL of water into a plastic bag.
Put the plastic cup in the bag, but do not let the cup fall.
Seal the bag. Make sure it is airtight.
Shake the bag so that the baking soda is exposed to the water.
5. Bring the inflated bag to the balance and record the final mass.
c. Mass of cup + baking soda + water:
6. Repeat steps 1-5 with 50mL of vinegar instead of water.
d. Mass of cup:
e. Mass of cup + baking soda:
f. Mass of cup + baking soda + Vinegar:
7. Calculate. The density of a substance is a measure of a substances mass divided by its
volume. If you know the density and volume of a substance its mass can thus
be calculated. Example: the density of mercury is 13.53g/mL. 20mL of mercury
thus has a mass of:
13.53g/mL x 20mL = 27.06g
Calculate the mass of water and vinegar used in this experiment.
Water has a density of 1g/mL
Vinegar has a density of 1.01g/mL
g. Water:
h. Vinegar:
Add b. and g. How does this value compare to c.?
Add e. and h. How does this value compare to f.?
Did your experiment show a conservation of matter?
Who’s Polluting the River?, Ben Bricker, Colby College, January 2012