Download Lab 5 A bagged chemical reaction

Student
A Bagged Chemical Reaction
NGSSS:
SC.912.P.8.2 Differentiate between physical and chemical properties and physical and chemical
changes of matter.
SC.912.P.8.8 Characterize types of chemical reaction, for example: redox, acid-base, synthesis
and single and double replacement reaction.
Background:
Chemical reactions occur when molecules come together to form new products. In our bodies
and environments, chemical reactions occur continuously to help run our lives. During a
reaction, chemical bonds are broken and remade. Usually, color changes, gases being
released, changes in temperature, and/or formation of solute characterize chemical reactions.
These events describe changes in energy or solubility of the compound, meaning new products
were produced.
Chemical reactions can be defined by a chemical equation in which reactants and products are
characterized by chemical symbols. All chemical reactions are accompanied by a change in
energy. Some reactions release energy to their surroundings (usually in the form of heat) and
are called exothermic. For example, sodium and chlorine react so violently that flames can be
seen as the exothermic reaction gives off heat. On the other hand, some reactions need to
absorb heat from their surroundings to proceed. These reactions are called endothermic. A
good example of an endothermic reaction is that which takes place inside of an instant '"cold
pack." Commercial cold packs usually consist of two compounds - urea and ammonium chloride
in separate containers within a plastic bag. When the bag is bent and the inside containers are
broken, the two compounds mix together and begin to react. Because the reaction is
endothermic, it absorbs heat from the surrounding environment and the bag gets cold.
Purpose of Lab/Activity:
 Observe the changes associated with a chemical reaction including heat changes,
changes in an indicator, bubble of gas released.
 Determine which compounds are reactants and which are products through the use of a
chemical equation.
 Use indicators in order to identify whether a solution is acidic or basic.
Safety:
 Remind students that there is NO eating or drinking during the lab.
 CO2 is produced in the bags. Make sure the area is well-ventilated before releasing all
the gas.
 Do not let students ingest baking soda or calcium chloride. Avoid contact with eyes or
mouth. If ingested in small amounts neither compounds are toxic, but if ingested in larger
amounts give student a full glass of water and contact a medical facility.
 Watch for bags exploding. Ensure the students shake the bag away from their faces and
clothes.
 Once bags get tightly filled with gas, release the CO2. If the bag does explode, all the
products are non-toxic and can be washed off.
 The bags can be disposed of in the trash because all products are non-toxic.
Chemistry HSL
Department of Science
Page 96
Student
Vocabulary: chemical reaction, reactants, products, exothermic, endothermic
Materials (individual or per group):
 Safety goggles & Lab apron
 4 tbsps Calcium chloride pellets (CaCl2)
 2 tbsp Baking soda, sodium bicarbonate
(NaHCO3)
 Phenol red solution
 Measuring cup or graduated cylinder
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2 plastic teaspoons
Plastic cup
4 1-gallon Ziploc-type bag
2 twist ties or rubber bands
Water
Procedures:
1. In a Ziploc type of bag, place 2 tablespoons of sodium bicarbonate (sodium hydrogen
carbonate) and a film-canister or vial (1/3 full of water or 30 ml) with 3 drops of the phenol
red indicator added to the water. Place canister/vial in the bag in the upright position.
Squeeze the excess air and seal the bag. Spill the water into the bag and record
observations. Record observations in Table 1.
2. To a second Ziploc type bag add 1 tablespoon of calcium chloride and add the same
amount of water as in the previous step but without the phenol red indicator. Repeat
procedure in step 1. Record observations in Table 1.
3. To a third Ziploc bag, add 2 tablespoons of calcium chloride into one corner of the bag,
twist off the corner to separate chemical from the rest of the bag and tie with a rubber
band or twist tie.
4. Into the opposite corner of the third bag, add 2 tablespoons of sodium bicarbonate and
twist off the corner to separate from the rest of the bag and tie with a rubber band or twist
tie.
5. Place the canister/vial with 30 ml of water in the middle of the bag in the upright position.
6. Squeeze the excess air and seal the bag.
7. Carefully untwist the 2 corners (if using rubber bands, use scissors to cut them careful
not to cut the bag) while the partner holds both corners apart.
8. Release both corners and allow all three chemicals to mix. Quickly observe any
immediate changes in the corners. Record all your observations in Table 1.
9. In a fourth bag repeat steps #3-8 but this time with 3 drops of the phenol red indicator to
the water. Record all your observations in Table 1.
Chemistry HSL
Department of Science
Page 97
Student
Observations/Data
Table 1- Physical and Chemical Changes
Physical or
Production Of
Chemical
Color change
gas
change
Temperature
change
NaHCO3 in
water + indicator
CaCl2 in water
NaHCO3 +
CaCl2 in water
NaHCO3 +
CaCl2 with water
+ indicator
solution
Observation/Data Analysis:
1. Which steps could be characterized as physical or chemical change? Justify your
reasoning
2. What observations confirm the presence of a chemical change?
3. Which process(es) would you characterize as exothermic? Explain.
4. Which process(es) would you characterize as endothermic? Explain.
Conclusion:
1. What was the function of the phenol red in the experiment?
2. During this reaction, baking soda (NaHCO3) is combined with calcium chloride (CaCl2) in
water. Write the balanced chemical equation for the reaction that occurred.
3. Give the names of all the compounds present in the chemical reaction you observed.
4. What type of gas is in your bags? How can you verify?
5. Propose an explanation for where the energy change originated.
6. Which general chemical principles or laws can you confirm in this investigation?
Chemistry HSL
Department of Science
Page 98