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Determining Endothermic and Exothermic Reaction (16 Favorites)

LAB in Classification of Reactions, Heat, Temperature, Exothermic & Endothermic. Last updated May 24, 2017.


Summary

In this lab, students will analyze evidence to determine if a chemical reaction releases energy and can be classified as an exothermic reaction or if it absorbs energy and can be classified as an endothermic reaction.

Grade Level

Middle and High School

Objectives

By the end of this lab, students should be able to

  • Discuss the meaning of both an endothermic reaction and an exothermic reaction.
  • Differentiate between an endothermic reaction and an exothermic reaction.
  • Interpret data to determine if an endothermic reaction or an exothermic reaction has occurred.

Chemistry Topics

This lab supports students’ understanding of

  • Energy & Thermodynamics
  • Endothermic & Exothermic reactions
  • Chemical Reactions

Time

Teacher Preparation: 1 hour

Lesson: 50 minutes – 1 hour

Materials (per group)

  • 2 foam cups
  • Black permanent marker
  • 2 paper towels
  • Citric acid, 25ml
  • Thermometer
  • Hydrogen peroxide, 50 ml
  • Stopwatch
  • Beef Liver, 1 x 1 inch cubes
  • Graduated cylinder
  • Baking soda, 1 tsp.
  • Teaspoon
  • Spoon

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.
  • Food in the lab should be considered a chemical not for consumption.

Teacher Notes

  • Assign students to small groups, approximately 4 students per group. Assign roles according to the attached roles sheets.
  • Prepare material for the groups ahead of time. This will include:
    • Create a tray/bin of materials for each group.
    • Pre-measure the liquids into small cups.
    • Cut the liver into 1 x 1 in. cubes.
    • Print and copy all resources the students will need.
  • Review lab procedures, safety, equipment and behavior.
  • This lab should follow a lesson on endothermic and exothermic reactions. Information from the following website can be helpful to compile notes:
  • Teachers should expect the following results:
    • The temperature of the citric acid solution and the baking soda should drop when the baking soda is added.
    • The temperature of the Hydrogen peroxide should rise when the liver is added.
  • Materials can be ordered from the following:

For the Student

Pre-lab Questions

  1. Define an endothermic reaction:
  2. Define an exothermic reaction:

Problem

How can you determine if a reaction gives off energy or absorbs energy?

Purpose

Some reactions need energy to occur. Other reactions release energy when they occur. In this lab, you will use evidence to determine if a chemical reaction releases energy.

Materials (per group)

  • 2 foam cups
  • Black permanent marker
  • 2 paper towels
  • Citric acid
  • Thermometer
  • Hydrogen peroxide
  • Stopwatch
  • Beef liver
  • Graduated cylinder
  • Baking soda
  • Teaspoon
  • Spoon

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow your teacher’s instructions for clean-up of materials and disposal of any chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.
  • Food in the lab should be considered a chemical not for consumption.

Procedure

  1. Take one foam cup and write the #1 on the outside. Take the other cup and write the #2 on the outside.
  2. Measure 25 mL of citric acid into a foam cup.
  3. Place the thermometer in the citric acid and record the initial temperature (⁰C) in the data table below.
  4. Add a teaspoon of baking soda (sodium bicarbonate) to the cup and stir. The thermometer should still be in the cup.
  5. Use a stopwatch to time 15-second intervals. After each 15 second interval, you should record the temperature of the reaction in the cup in the data table below.
  6. Record the temperature 12 times, every 15 seconds, during a total of 3 minutes.
  7. Take the thermometer out of the cup, rinse it and wipe it dry with a paper towel.
  8. Measure 25 mL of hydrogen peroxide, and add it to the 2nd foam cup.
  9. Place the thermometer in the cup and record the temperature in the data table below.
  10. Place a small piece of liver in the hydrogen peroxide.
  11. Again, use a stopwatch to time 15-second intervals. After each 15 second interval, you should record the temperature of the reaction in the cup in the data table below.
  12. Record the temperature 12 times, every 15 seconds, during a total of 3 minutes.
  13. Take the thermometer out of the cup, rinse it and wipe it dry with a paper towel.

Data

Time

Temperature (°C)

Citric Acid Solution

Hydrogen peroxide

Initial Temperature,

0 seconds

15 seconds

30 seconds

45 seconds

1 minute

1 minute, 15 seconds

1 minute, 30 seconds

1 minute, 45 seconds

2 minutes

2 minutes, 15 seconds

2 minutes, 30 seconds

2 minutes, 45 seconds

3 minutes, seconds

Analysis

  1. What happened to the temperature in cup #1 during the 3 minutes of the reaction?
  2. What type of reaction, endothermic or exothermic, occurred in this cup? How do you know?
  3. What happened to the temperature in cup #2 during the 3 minutes of the reaction?
  4. What type of reaction, endothermic or exothermic, occurred in this cup? How do you know?
  5. How could you explain the changes in the temperatures of cup #1 and cup #2?
  6. If you were to repeat the experiment, do you think you would get the same results?
  7. Why would it be important to repeat the experiment?
  8. What would happen if you used a slice of carrot instead of the liver?
  9. If you added more baking soda to the citric acid, would it cause a greater temperature change?

Conclusion

Now that you have completed the lab, it is good to know how endothermic reactions and exothermic reactions are used in everyday living. The following are some endothermic and exothermic reactions:

Exothermic Reactions:

Endothermic reactions:

Snow clouds forming

Frost melting to water vapor

Rusting Iron

Melting Ice cubes

Freezing ice cubes

Baking bread

Burning sugar

Cooking eggs

Imagine that you are the CEO of a company that sells camping equipment. Why is it important to know about endothermic reactions and exothermic reactions when you are trying to create and sell products to the public?