TEKS-Based Activity for Grade 8
It’s in the Bag!
Description:
In this activity, students measure temperature changes in endothermic and
exothermic processes to illustrate interactions between matter and energy.
Time Frame:
2 lessons (45 minutes each)
Correlation to Texas Essential Knowledge and Skills:
During this activity, students will be exposed to the following Texas Essential
Knowledge and Skills:
(8.10) Science concepts. The student knows that complex interactions occur
between matter and energy. The student is expected to:
(C)
identify and demonstrate that loss or gain of heat energy occurs
during exothermic and endothermic chemical reactions.
Note: The TEKS listed here are the main content TEKS for this activity;
however, this activity may also cover additional content and process skills
included in other TEKS.
Materials:
Metric measuring spoons (1 set per student group)
Zipper-type freezer sandwich bag (3 per student group)
Baking soda (15 mL per student group)
Calcium chloride dihydrate powder (15 mL per student group)
Water (15 mL per student group)
Universal indicator with interpretation chart (1 dropper bottle of solution per
class)
Clear plastic cups (3)
Temperature probe (1 per student group)
Marker (1 per student group)
Colored pencils (3 different colors per student group)
Graph paper (1 page per student group)
Safety goggles (1 per student)
Safety aprons (1 per student)
It’s in the Bag! student investigation pages (included at the end of this activity)
Background Information:
In this activity, the temperature change students observe in Bag 1 is an
endothermic process in which heat is absorbed, whereas the temperature change
in Bag 2 is an exothermic process in which heat is released. However, chemical
reactions are not occurring in either Bag 1 or Bag 2, as the substances are simply
being dissolved. The changes in temperature, then, are the result of a physical
change and not a chemical reaction.
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
When the contents of Bag 1 are added to Bag 2, a gas is produced, and the final
substance has new properties. In this case, the temperature change observed
when the contents of the two bags are mixed does result from a chemical
reaction. The result is an exothermic chemical reaction.
Advance Preparation:
1. Place enough baking soda, calcium chloride dihydrate powder, and water in
three appropriately labeled plastic cups so that each student group will have
15 mL of each.
2. Set up a materials distribution center so that students can easily collect all the
materials needed for this activity.
3. Make copies of It’s in the Bag! student investigation pages for each group.
4. Give students an opportunity to practice using the temperature probes before
beginning this learning experience. Temperature probes, rather than
thermometers, should be used for the temperature readings because it allows
for more frequent readings and therefore a better analysis of the resulting
temperature changes. If thermometers are substituted for the probes, readings
should be made at 20-second intervals, and the Temperature Over Time table
should be adjusted accordingly. Nevertheless, more frequent readings made
by the temperature probes are best for analyzing this investigation.
Procedures:
SAFETY: Students should wear eye protection and safety aprons. They should not
taste or smell any of the materials.
1. Talk students through the investigation pages. Be sure that students note they
will be recording temperature over a period of time. Be sure students are
familiar with the use of temperature probes before they begin this activity.
2. Have students work in groups to complete the It’s in the Bag investigation
pages.
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
It’s in the Bag!
Student Investigation Pages
Part A
Materials for Part A:
Metric measuring spoons
1 zipper-type sandwich bag
10 mL baking soda (NaHCO3)
10 mL calcium chloride (CaCl2)
10 mL water
Universal indicator
Safety goggles
Safety apron
Procedures:
SAFETY: Wear eye protection and a safety apron. Do not taste or smell any of the
materials.
In this activity you will combine chemicals to demonstrate how substances may
chemically react to form new substances.
1. Add 10 mL of calcium chloride (CaCl2) and 10 mL of baking soda (NaHCO3) to the
sandwich bag. Seal the bag and mix the two chemicals thoroughly by kneading
the bag. Observe the contents of the bag and record your observations in Data
Table 1.
2. Be ready to make immediate and constant observations during this step. Open
the bag and add 10 mL of water and 4 drops of universal indicator. Quickly seal
the bag and knead the bag to mix the contents thoroughly. Observe the
contents of the bag for 3 minutes. Feel the bag every 10-15 seconds. Does the
temperature of the bag change? Record your observations in Data Table 1.
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
Temperature Based on Touch
Without water or indicator
With water and indicator
Color
Temperature
based on
touch
Other
observations
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
PART B:
Materials for Part B:
Metric measuring spoons
2 zipper-type sandwich bags
5 mL baking soda (NaHCO3)
5 mL calcium chloride (CaCl2)
5 mL water
Universal indicator
Temperature probe
Marker
3 different colors of colored pencils
Graph paper
Safety goggles
Safety apron
Procedures:
SAFETY: Wear eye protection and a safety apron. Do not taste or smell any of the
materials.
In the next part of this investigation, you will further analyze the mixing of
substances to determine if a chemical reaction is occurring. Use this table to help
analyze your results.
Indicators of a Chemical Reaction
Yes
Temperature change with no other changes
No

Temperature change along with other changes

Gas produced along with other changes

Precipitate forms

Color change occurs

As shown in the Indicators of a Chemical Reaction table above, a change in
temperature is not necessarily evidence of a chemical reaction. Dissolving salts in
water can result in a temperature change, but it is not a chemical reaction. Other
factors, such as the production of a gas or the formation of a precipitate, would
need to be present.
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
Remember:
•
An exothermic reaction occurs in a chemical reaction when heat is released
during the mixing of substances—this feels like the substances are getting
warmer.
•
An endothermic reaction occurs when heat is absorbed during the mixing of
substances in a chemical reaction—this feels like the substances are getting
cooler.
1. Label the sandwich bags 1 and 2. Add 5 mL of baking soda (NaHCO3) to Bag 1
and add 5 mL of calcium chloride (CaCl2) to Bag 2.
2. Add 5 mL of water to Bag 1. IMMEDIATELY insert the temperature probe and
measure the temperature. Continue to take temperature readings at 10-second
intervals for 2 minutes. Record the data you collect in the Temperature Over
Time table.
What happened to the temperature?
Was a new product produced or did the original substance simply dissolve in
water?
Based on the information found in the Indicators of a Chemical Reaction table,
was this a physical or a chemical change? Support your conclusion.
3. Add 5 mL water to Bag 2. IMMEDIATELY insert the temperature probe, and
measure the temperature. Continue to take temperature readings at 10-second
intervals for 2 minutes. Record the data you collect in the Temperature Over
Time table.
What happened to the temperature?
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
Was a new product produced or did the original substance simply dissolve in
water?
Based on the information found in the Indicators of a Chemical Reaction table,
was this a physical or a chemical change? Support your conclusion.
4. Add 3–4 drops of universal indicator to Bag 2 and record the pH measurement in
the Temperature Over Time table. Add 3–4 drops of universal indicator to Bag 1
and record the pH measurement in the table. Compare the pH results of the two
bags and describe what you know about their pH readings
5. Take 15 mL of the contents from bag 2 and add it to bag 1. IMMEDIATELY
insert the temperature probe, and measure the temperature. Continue to take
temperature readings at 10-second intervals for 2 minutes. Record this data in
the Temperature Over Time table.
What happened to the temperature?
Was a new product produced or did the two substances dissolve?
Based on the information found in the Indicators of a Chemical Reaction table,
was this a physical or a chemical change? Support your conclusion.
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TEKS-Based Activities
Grade 8—Itʼs in the Bag!
Temperature Over Time
Time
Bag 1
Bag 2
Bag 1 + 2
O seconds
10 seconds
20 seconds
30 seconds
40 seconds
50 seconds
60 seconds
70 seconds
80 seconds
90 seconds
100 seconds
110 seconds
120 seconds
pH
Final color
6. Use graph paper to construct a graph of the temperature changes. Use the
colored pencils to represent the results of Bag 1, Bag 2, and Bag 2 + 1. What can
you conclude about the temperature changes observed in each bag?
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