1. Pour 15 milliliters of distilled water into the Erlenmeyer flask.
2. Record the initial temperature of the water using a thermometer. Make sure the thermometer is fully immersed in the water by holding the flask at an angle if necessary.
3. Measure 1.92 grams of citric acid using a weighing boat and set it aside.
4. Measure 2.52 grams of sodium bicarbonate using another weighing boat.
5. Pour the citric acid into the same weighing boat as the sodium bicarbonate. Use a scoop to thoroughly mix the substances together, being careful not to spill.
6. Transfer the mixture of citric acid and sodium bicarbonate into the Erlenmeyer flask.
7. Stir the mixture with the thermometer.
8. Watch the thermometer for a couple of minutes and record the lowest temperature it reaches. This will be the final temperature of the solution.
9. Calculate the change in temperature by subtracting the initial temperature from the final temperature.
By following these steps and recording your findings in a table, you will be able to observe the temperature change that occurs during the reaction between citric acid and sodium bicarbonate.