Reaction in a Bag Directions
Investigating Endothermic and Exothermic Reactions
Read through these two experiments. Then respond to the safety questions. Have your teacher
check your answers BEFORE beginning the experiments.
Experiment 1
This first experiment is not a chemical reaction, but merely the physical act of dissolving a solute in a
solvent. When ammonium nitrate is dissolved in water, heat is required to break apart the forces
holding the ammonium nitrate together as a crystal.
Materials
•
Ammonium nitrate (NH4NO3)
•
Thermometer
•
Scoopula
•
Small graduated cylinder
•
Tap water
•
Ziplock bag
Safety Precautions
Ammonium nitrate is slightly toxic by ingestion and may be a body tissue irritant. Wear goggles at all
times and wash your hands when finished. If the bag begins to get too cold to handle, put it down
immediately to avoid skin damage.
In other words, do not eat it and do not touch it with your bare skin.
Procedures
1.
Place one scoopful of ammonium nitrate into the zip lock bag provided. Tilt the bag so all the
material falls into one corner of the bag.
2.
Measure 5 mL of water into the graduated cylinder and carefully pour this into the bag with the
ammonium nitrate.
3.
Place the thermometer into the substance and record the temperature.
4.
Close the zip lock bag by sealing it tightly across the top.
5.
Gently squeeze the bag to dissolve all the ammonium nitrate in the water.
6.
Observe what happens when the ammonium nitrate dissolves and record these observations.
7.
Open the bag, place the thermometer into the substance and record the temperature.
8.
Rinse out the bag at the sink and dry the inside of it with a paper towel before proceeding onto
the next experiment.
Experiment 2
Calcium oxide is also known as lime or quicklime and is used to make plaster, mortar, bricks, and
many other construction materials. When calcium oxide is added to water, calcium hydroxide is
produced. Calcium hydroxide is used to treat acidic soils, soften water, and in the preparation of
many building materials.
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Materials
•
Calcium oxide (CaO)
•
Thermometer
•
Scoopula
•
Small graduated cylinder
•
Tap water
•
Ziplock bag
Safety Precautions
Calcium oxide is a corrosive material and severe body tissue irritant. Avoid all contact with calcium
oxide. Reaction of calcium oxide and water will produce large amounts of heat and skin burns are
possible. Do not handle the bag if it becomes too hot and do not remove the product until it has
cooled to room temperature. Do not tightly seal the bag – allow the hot air and water vapor to
escape. Wear goggles at all times and wash your hands when finished.
In other words, do not eat it and do not touch it with your bare skin.
Procedures
1.
Place one or two lumps of calcium oxide into the zip lock bag provided. Tilt the bag so all the
material falls into one corner of the bag.
2.
Measure 5 mL of water into the graduated cylinder and carefully pour this into the bag with the
calcium oxide.
3.
Measure out another 4 mL of water into the graduated cylinder. Set to the side to use in a later
step.
4.
Place the thermometer into the substance and record the temperature.
5.
Do NOT seal the bag. Gently squeeze the bag to break the calcium oxide lump apart. Do not
use anything hard or sharp to break apart the calcium oxide — fingertips work fine.
6.
As soon as the calcium oxide begins to heat up, add the 4 mL of water you set aside in the
graduated cylinder.
7.
Place the thermometer into the substance again and record the temperature.
8.
Loosely close the zip lock bag – do NOT tightly seal the bag.
9.
Keep squeezing the bag to thoroughly mix the water and calcium oxide. The result should be a
white solution of calcium hydroxide.
10.
Observe what happens when the calcium oxide reacts with the water and record these
observations.
11.
Open the bag, place the thermometer into the substance again and record the temperature.
12.
After the reaction has cooled to room temperature, rinse out the bag at the sink and dry the
inside of it with a paper towel.
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Name
Class
Date
Reaction in a Bag
Investigating Endothermic and Exothermic Reactions Student Worksheet
Safety Precautions
Read through these two experiments. Then respond to the safety questions below. Have your
teacher check your answers BEFORE beginning the experiments.
1.
Why should you make sure that you completely close the bag in the first experiment, but leave
it open for the second?
2.
How will you make sure that you DO NOT get any of these chemicals ON or IN you?
Observations
3.
Record your general observations for experiment 1.
4.
Temperature of ammonium nitrate before is
5.
Record your general observations for experiment 2.
6.
Temperature of calcium oxide before is
Afterwards, it is
.
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. Afterwards, it is
.
. During the experiment, it is
.
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Analysis and Conclusion
7.
Draw and label the energy diagrams that correspond with each of the experiments.
Experiment 1
Experiment 2
8.
Was experiment 1 an exothermic or endothermic reaction? Why?
9.
How would the temperature of the bag in experiment 1 be affected if twice as much water were
added? Why?
10.
How should the chemical equation be written for the reaction in experiment 1? Why?
NH4NO3 + heat → NH4NO3
or
NH4NO3 → NH4NO3 + heat
11.
Was experiment 2 an exothermic or endothermic reaction? Why?
12.
How should the chemical equation be written for the reaction in experiment 2? Why?
CaO + H2O + heat → Ca(OH)2
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or
CaO + H2O → Ca(OH)2 + heat
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