Inner Space

Source Institutions

Add to list Go to activity
Activity link broken? See if it's at the internet archive
In this activity, learners discover that there is space between molecules even in a cup "full" of water. They first fill a cup with marbles, and then add sand to fill the gaps between the marbles. This serves as a model when they add sand and salt to a full cup of water, discovering that more salt will fit into the tiny spaces between molecules. Provides an opportunity to discuss the use of models in science, and the benefits and limits of marbles as a model for molecules. Extensions include trying different substances, and comparing densities of saltwater and plain water. Part of the "No Hassle Messy Science with a Wow" activity guide by OMSI, where all activities use only household materials.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
10 to 30 minutes

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

Age Range:
Ages 6 - 14

Resource Types:
Activity, Experiment/Lab Activity, Lesson/Lesson Plan, Model

English, Spanish

Materials List (per group of students)

  • 5 plastic cups, 8-oz. or smaller
  • 1 cup water
  • 1 pop-top squeeze bottles (e.g., water or sport drink) 16 oz. or larger
  • 1 cup marbles (or other small, spherical objects)
  • 1 large jar or margarine tub, 2- to 4-cup capacity (multiple groups can share)
  • 1/2 cup salt
  • 1/2 cup sand
  • 2 plastic spoons
  • (optional) measuring spoons
  • 1 cafeteria tray
  • 2 coffee filters
  • 1 strainer (multiple groups can share)
  • 1 bowl (multiple groups can share)


  • Physical Sciences
    • Chemistry
      • Solutions
    • States of Matter
      • Solids
      • Liquids
    • Structure and Properties of Matter
      • Mass and Weight
      • Volume and Density


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Foreign language versions of this resource:

Includes alignment to state and/or national standards:

Access Rights:

  • Free access


  • Oregon Museum of Science and Industry


  • All rights reserved, Oregon Museum of Science and Industry, 2007

Funding Sources:

  • National Science Foundation
  • Camille and Henry Dreyfus Foundation