Reaction in a Bag

A ziplock bag is inflated by mixing three substances in it

Scientific name: Exothermic reaction between calcium chloride and sodium bicarbonate. Color of the indicator changes due to the formation of carbonic acid.


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Wear eye protection goggles. Use gloves.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

CaCl2 + 2 NaHCO3 → CaCO3 + 2 NaCl + CO2 + H2O

Step-by-step instruction

  1. Put 2 teaspoons of calcium chloride in a ziplock bag.
  2. Put one teaspoon of sodium bicarbonate in the other corner of the ziplock bag.
  3. Carefully take the bag and pour 10 ml of phenol red into it so that the components do not mix.
  4. Close the ziplock bag and mix ingredients.
  5. Observe how the bag inflates and the color changes.

Scientific background

Interaction of calcium chloride with sodium bicarbonate leads to the formation of carbon dioxide that fills the bag.

This reaction is exothermic, and therefore, it forms calcium carbonate and carbon dioxide, instead of calcium hydrogen carbonate. The color change of the indicator is caused by changes in the reaction medium due to the formation of carbonic acid.


Published on 15 May 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst