This experiment is easily accessible and can be easily scaled for different environments. For younger children, the reaction should act as a demonstration only, performed by the instructor. In this case they can observe the reaction and make note of what they see and feel without having contact with the reactants. In older age ranges, students may be allowed to set up the reaction themselves with the appropriate safety gear included gloves, goggles and an apron/coat to protect clothing. Students should be monitored to prevent prolonged chemical contact or ingestion.
Science Discipline:
Chemistry
Topic:
Exothermic chemical reactions
Materials:
- Calcium chloride, CaCl2, solid, 100 g
- Phenol red solution, 0.02%
- 70 mL Pipet
- Sodium bicarbonate, NaHCO3, solid, 40 g
- Water, distilled or deionized, 70 mL
- Beakers, 50-mL (2)
- Beakers, 100-mL (2)
- Graduated cylinder, 10-mL
- Pen, labeling
- Sealable, zipper-lock plastic bags
- Teaspoon and tablespoon scoops
- Wash bottle filled with distilled or deionized water
Instructions
- Label two 100-mL beakers “calcium chloride” and “sodium bicarbonate,” respectively fill each beaker about one-half full with the appropriate solid
- Obtain both a teaspoon and tablespoon scoop to dispense the sodium bicarbonate and calcium chloride, respectively
- Store the scoops in their respective beakers (Make sure that each scoop is only used with the same chemical it originally contacted)
- Obtain 40 mL each of phenol red and distilled water in separate, labeled, 50-mL beakers
- Use a 10-mL graduated cylinder or pipet to dispense the liquids as needed in the following steps
- Be sure to rinse the cylinder with distilled water after using the phenolphthalein indicator before using it again
- Lay a plastic bad flat on the table
- Place 1 TBSP of calcium chloride, 1 tsp of baking soda and 10mL of phenolphthalein indicator in separate locations inside the bag
- Push out excess air and seal the bag before mixing the contents thoroughly
- Students are now able to observe the reaction and feel the bag as it warms up
- If gas builds up, open the bag slightly away from the faces of anyone nearby
- Rinse with water for cleanup
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Questions
When did a reaction take place and how did you know?
The reaction took place directly after the solids were combined with water, and was confirmed with a change in temperature and color due to the phenol indicator.
Was a gas produced? Why or why not?
Yes, CO2 was produced and can be seen in the form of bubbles and pressure build up in the bag.
Was there a change in the temperature of the bag? Why do you think that is?
There was an increase in temperature, indicating a release in energy from an exothermic reaction. (Releases heat)
What color changes were observed during the reaction?
The color is likely to shift from red to a more yellow color, but only when both solids are present. This is indicative of a change in pH caused by the production of hydrochloric acid.