As The Stomach Churns

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In this chemistry activity, learners fill two test tubes with a solution of "artificial stomach fluid," consisting of hydrochloric acid in the same concentration as in human stomachs, some soap to create bubbles, and an acid base indicator. To one tube they add an antacid powder; in the other tube, they add an anti-gas powder. By observing the resulting reactions, learners observe how antacids and antigas medicines work on their stomach fluids. Cost estimates are per 100 learners. For safety reasons, this activity works best as a demonstration for younger audiences.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
5 to 10 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 14 - adult

Resource Types:
Activity, Demonstration, Experiment/Lab Activity, Simulation


Materials List (per group of students)

  • One 25-ml graduated cylinder
  • Two plastic test tubes (about 100-ml) with screw caps
  • Two small (about 4-oz) jars or containers with lids
  • Two 1-ml or ¼-tsp measuring spoons
  • One 250-ml squeeze bottle
  • CaCO3 (calcium carbonate powder) (keep 500 g on hand)
  • 1M HCl (hydrochloric acid) (keep 1 L on hand) — OR — concentrated (12M) HCl (keep 200 ml on hand)
  • Dish-washing soap (keep 8 oz on hand)
  • Bromocresol green solution (keep 50 ml on hand) — OR — bromphenol blue sodium salt (keep 10 g on hand)
  • One 1000-ml glass bottle
  • One large jar (500-ml) with lid
  • One medium to large jar (250-ml or larger) with a lid
  • One 50-ml bottle
  • 30% simethicone emulsion (Dow-Corning® 7-9245, also known as polydimethylsiloxane) (keep 4 oz on hand) OR “SafeStepTM” de-icer (contains mostly KCl)
  • in place of simethicone, potassium chloride (KCl) has been effective


  • Life Sciences
    • Human Body
      • Digestion
      • Health and Nutrition
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
    • States of Matter
      • Gases


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access



Funding Source:

  • National Science Foundation