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CHEMISTRY IN A ZIPLOC BAG
Introduction:
The science of chemistry is based upon observation. In this experiment, you will observe a chemical reaction
and a physical process. An observation is a statement of fact, based on sensory data. For example, “the liquid
is clear and colorless” is an observation. An interpretation is a judgment or opinion about what is being
observed. For example, “the liquid is water” is an interpretation.
You will make observations on the physical properties of some of the chemicals used in the lab. Physical
properties can be intensive or extensive. Extensive physical properties depend on the amount of the substance.
Examples include mass, length and volume. Intensive physical properties do not depend on the amount of
substance present. Examples include density, color and shape.
You will also determine whether certain processes are endothermic or exothermic. Endothermic means that
heat is being taken in. Melting is an example of a physical process that requires heat and therefore is
endothermic. Exothermic means that heat is being released. Freezing is an example of a physical process that
releases heat and is therefore exothermic.
Pupose:
To make observations about a physical process (dissolving) and a chemical reaction.
To distinguish between an exothermic process and an exothermic process.
Safety:
Wear goggles and aprons at all times.
Materials:
2 Ziploc snack-size bag
Small beaker
1 tsp baking soda
1tsp calcium chloride
2 x 10 mL water
1 mL methyl red or phenol red indicator solution
Procedure:
1. Put one teaspoon of baking soda (sodium bicarbonate) into one Ziploc bag. In the data table, record at least
two physical properties of the sodium bicarbonate.
2. Add 10 mL of water to the bag and dissolve the baking soda. Feel the bag and record any temperature
change.
3. Put one teaspoon of calcium chloride into the second Ziploc bag. In the data table, record at least two
physical properties of the calcium chloride.
4. Add 10 mL of water to the second Ziploc bag and dissolve the calcium chloride. Feel the bag and record
any temperature change.
5. Add 1 mL of methyl red or phenol red solution to the baking soda solution. In the data table, make at least
two observations of physical properties about the indicator solution.
6. Squeeze the air out of the bag with the calcium chloride solution, leaving one corner open. Pour the baking
soda/indicator solution into the opening of the bag. Quickly seal the bag shut.
7. Mix the contents by squeezing the bag gently. Record all observations in the data table.
8. Clean up by throwing away your baggie and its contents in the trash. Make sure the lab bench and sink are
perfectly clean.
Chemistry in a Ziploc Bag
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Data:
Example Data
Baking soda
(Sodium bicarbonate)
Formula: NaHCO3
Physical Property #1:
Ex: white
Intensive / Extensive
Physical Property #2:
Ex: solid
Intensive / Extensive
Observation(s):
Beaker feels cold
Formula: CaCl2
Endothermic/Exothermic
Physical Property #1:
Ex: white crystals
Intensive / Extensive
Physical Property #2:
Ex: solid
Intensive / Extensive
Calcium chloride
dissolving in water
Observation(s):
Baggie feels warm
Endothermic/Exothermic
Indicator Solution
Physical Property #1:
Ex: liquid
Intensive / Extensive
Physical Property #2:
Ex: red
Intensive / Extensive
Sodium Bicarbonate
dissolving in water
Calcium chloride
Phenol red
Reaction
Observations:
-The baggie feels cold
-The solution turns red, then yellow, then back to red (usually)
-The bag fills with gas
Questions:
1.
Is solubility (the ability to dissolve in another substance) a chemical property, an intensive physical
property or an extensive physical property? Explain your reasoning.
Intensive physical property; the amount you have doesn’t matter – 1 gram of a substance is
just as (in)soluble as 100 grams of the substance
2.
List at least two observations that indicate that a chemical reaction took place.
-gas was produced; color change in the indicator; change in temperature
3.
Calcium chloride reacted with the sodium bicarbonate to produce sodium chloride, calcium carbonate,
carbon dioxide and water. Write the balanced equation for this reaction.
Chemistry in a Ziploc Bag
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CaCl2 + 2 NaHCO3  2 NaCl + CaCO3 + CO2 + H2O
4.
Classify this reaction as exothermic or endothermic. Explain your reasoning.
Endothermic; the baggie felt cold so heat was absorbed
5.
If you had doubled the ingredients, what would have happened in this experiment?
The amount of gas produced would have increased
Chemistry in a Ziploc Bag
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Ziploc Bag Lab
TEKS:
Scientific Process Skills:
Readiness Standards:
Supporting Standards:
1ABC; 2FI
4A; 7B; 11C
4B; 7D;
Note:
Methyl red: below 4.4, red; above 6.2, yellow; orange in-between
Phenol red: below 6.8, yellow; above 8.4, red; orange in-between
*A funnel may be used to pour the contents of one bag into the contents of another bag.
Clean-up:
The contents of the bags can be filtered to remove the calcium carbonate. The filtrate may
washed down the sink.
Chemistry in a Ziploc Bag
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