Natural Buffers

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Learners use a universal indicator to test the amount of sodium hydroxide needed to change the pH of plain water compared with the amount needed to change the pH of gelatin. Learners discover that living systems must maintain a constant pH to survive, and buffers help them maintain a constant pH in the presence of excess acid or base. This activity is currently used in the Biochemistry Unit in OMSI's Chemistry Lab. 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:
Under 5 minutes

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

Age Range:
Ages 14 - adult

Resource Types:
Activity, Demonstration, Experiment/Lab Activity


Materials List (per group of students)

  • Two 50-ml flasks or beakers
  • Two 25-ml graduated cylinders
  • One 60-ml dropper bottle
  • One 30-ml dropper bottle
  • Universal indicator (keep 500 ml on hand)
  • Two 250-ml squirt bottles
  • Experiment copy with the universal indicator chart in color
  • 1M NaOH (sodium hydroxide) (keep 200 ml on hand) —OR— solid NaOH (keep 50 g on hand)
  • Dry gelatin (keep 250 g on hand)
  • 95% C2H5OH (ethyl alcohol or ethanol) (keep 500 ml on hand )
  • 250- to 500-ml plastic storage bottle
  • Small pipettes


  • Life Sciences
    • Cells
    • Human Body
  • Physical Sciences
    • Chemistry
      • Acids and Bases
      • Solutions


To use this activity, learners need to:

  • see
  • see color
  • 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