Exothermic and Endothermic Reactions
Name______________________________
Date___________________Period_______
Introduction: Temperature change is one of the ways you know that a chemical reaction has
occurred. Chemists use the term exothermic to describe a reaction which gives off heat and
endothermic to describe reactions that take in heat. We are often more familiar with exothermic
reactions. Endothermic reactions are less familiar to us.
● How would a test tube containing an endothermic reaction feel to the touch?
● Why would it?
In this activity you will mix 3 substances in water and measure the temperature.
Materials: 3 test tubes, test tube rack, thermometer, water, sodium hydroxide, ammonium
nitrate, potassium nitrate,
Procedure:
1. Put 10 mL of water into each of the 3 test tubes. Take the temperature of the water in
each test tube and record it in the data table.
2. Add 3 pellets of sodium hydroxide to test tube 1 with forceps (do not touch with your
hands). Place a thermometer in the test tube and stir gently. Record the temperature of
greatest change in the data table.
3. Zero the scale.
4. Place a piece of weighing paper on the scale. Reset the scale to zero again
5. Add enough ammonia nitrate to the paper so that the scale reads about 1.5 grams.
6. Pour the ammonium nitrate into the second test tube.
7. Place the thermometer in the test tube and stir gently. When it has finished changing,
record the temperature in the data table.
8. Repeat the same procedure with potassium nitrate, using a new piece of weighing paper.
Test Tube
Sodium hydroxide
Ammonium nitrate
Potassium nitrate
Temperature of Water
(start)
Temperature of Water
(final)
Analysis:
1. Which reactions were exothermic? How can you tell?
2. Do the chemicals on the reactant side or the chemicals on the product side have more energy
in an exothermic reaction?
3. Does the energy go from the surrounding to the chemicals or from the chemicals to the
surroundings in an exothermic reaction?
4. Which reactions were endothermic? What is your evidence?
5. Define endothermic and exothermic in your own words.
Conclusion
(Summarize what you learned about exothermic and endothermic reactions from this lab.)