Name:__________________________________________ Date:________________________ Class:____________________
What makes a chemical reaction endothermic or exothermic?
This activity was adapted from the lab investigation: Endothermic, Exothermic, & Chemical Change on The American
Chemical Society website: http://highschoolenergy.acs.org/content/hsef/en/how-can-energy-change/exothermic-endothermicchemical-change.html
1.
2.
Define the terms endothermic and exothermic. Be sure to include the term energy in your definition.
a.
Endothermic-
b.
Exothermic-
Data Collection- In the Lab (Wear safety goggles and follow all standard safety procedures)
a.
Reaction 1- Sodium Bicarbonate and Acetic Acid
i. Obtain a 250 mL beaker and add 20 mL of acetic acid (vinegar) to the beaker.
ii. Place the temperature probe in the beaker and allow the temperature to stabilize. Record this
temperature in the data table as the initial temperature.
iii. Leave the temperature probe in the beaker and add 0.5 grams of solid sodium bicarbonate (baking
soda) to the beaker. Monitor the temperature and record the final temperature in the data table once
the temperature stabilizes.
iv. Wash the contents of the beaker down the drain with plenty of water.
b.
Reaction 2- Sodium Bicarbonate Solution and Calcium Chloride
i. Add 50 mL of water to a clean 250 mL beaker and add 1.5 grams of sodium bicarbonate (baking
soda) to make an aqueous sodium bicarbonate solution.
ii. Place the temperature probe in the beaker and allow the temperature to stabilize. Record this
temperature in the data table as the initial temperature.
iii. Leave the temperature probe in the beaker and add 0.5 grams of calcium chloride to the beaker.
Monitor the temperature and record the final temperature in the data table once the temperature
stabilizes.
iv. Wash the contents of the beaker down the drain with plenty of water.
Reactants
Sodium bicarbonate
(solid) + acetic acid
Sodium bicarbonate
(aqueous) + calcium
chloride
Initial Temperature
(Ti)
Final Temperature
(Tf)
Temperature Change
(T)
Endothermic or
Exothermic?
3.
4.
For the reaction of sodium bicarbonate and acetic acid:
a. Write the balanced chemical equation for the reaction: sodium bicarbonate reacts with acetic acid to form
water, carbon dioxide, and sodium acetate.
b.
What evidence is there that a chemical reaction has occurred?
c.
Is this reaction endothermic or exothermic? What evidence do you have to support your claim?
d.
Recall from the video that energy is used to break bonds in the reactants and energy is released when the
bonds of the products form. Based on your answer to part c is more energy required to break the bonds of the
reactants in this reaction or is more energy released from the formation of the products? Explain.
e.
Develop a model to visualize the relative (non-numerical) quantity of the bond energy of the reactants and
the bond energy of the products.
For the reaction of sodium bicarbonate and calcium chloride:
a. Write the balanced chemical equation for the reaction: sodium bicarbonate (aqueous) reacts with calcium
chloride to form carbon dioxide gas, water, sodium chloride and calcium carbonate.
b.
What evidence is there that a chemical reaction has occurred?
c.
Is this reaction endothermic or exothermic? What evidence do you have to support your claim?
d.
Recall from the video that energy is used to break bonds in the reactants and energy is released when the
bonds of the products form. Based on your answer to part c is more energy required to break the bonds of the
reactants in this reaction or is more energy released from the formation of the products? Explain.
e.
Develop a model to visualize the relative (non-numerical) quantity of the bond energy of the reactants and
the bond energy of the products.