Rock Bottoms

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Learners add acid rain (nitric acid) to two cups that represent lakes. One cup contains limestone gravel and the other contains granite gravel. Learners also add an indicator to each solution that shows any change in the acidity of the "lakes." The indicator shows that the limestone lake returns to neutral while the gravel lake becomes acidic. This activity is part of the Environmental Chemistry Unit in OMSI's Chemistry Lab. Materials estimates are for 100 uses. For safety reasons, this activity works best as a demonstration for younger audiences.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
5 to 10 minutes

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

Age Range:
Ages 14 - adult

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


Materials List (per group of students)

  • Two large, clear plastic jars (about 1 quart) with screw on lids (old instant coffee jars work well) (keep four on hand) Keep 6 lids on hand
  • 2 cups limestone or marble chips
  • 2 cups granite pebbles or gravel
  • One 10-ml graduated cylinder
  • One 250-ml squeeze bottle
  • One 30-ml dropper bottle
  • Bromcresol green indicator (keep 5 g on hand)
  • 0.03M HNO3 (nitric acid) (keep 2 liters on hand) —OR— concentrated (15.8M) HNO3 (Keep 50 ml on hand)
  • Two 1 L and one 250 ml storage bottles


  • Earth and Space Science
    • Earth Processes
      • Weather and Climate
    • Earth Structure
      • Rocks and Minerals
    • Earth's History
  • Life Sciences
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
      • Solutions
  • The Nature of Science
    • Science and Society

Informal Categories

  • Nature and Environment
  • Science Festivals Activity


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