A Little Drop of Water: Cohesion

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Learners explore water's property of cohesion through two investigations. In Drops on a Penny, they see how many drops of water or other fluids can fit on a penny before the drops run over, and in Filled to the Brim they fill a cup to the brim with water, then slowly add paperclips to observe what happens. In both activities, learners make predictions about what will happen and compare their predictions with observations. Learners also use marshmallows to become familiar with the atomic structure and behavior of water molecules, including the attraction between water molecules known as surface tension. The student journal includes a Science @ Home activity for experiencing how water molecules stick together when flowing from a can with holes.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
1 to 2 hours

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

Age Range:
Ages 8 - 14

Resource Types:
Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Different types of marshmallows: multi-colored or large and small
  • Toothpicks
  • 9 oz cup
  • Eyedropper or straw
  • Paper towel
  • Hundreds of assorted pennies -- new, old, shiny, dirty and discolored
  • Two 1/2 liter water bottles filled with tap water
  • Other liquids to serve as variables: Soapy water, salt water, white vinegar, Karo syrup, baby oil, isopropyl alcohol, seltzer water
  • Waxed paper
  • Paper towel
  • Aluminum foil
  • Wood block or cardboard
  • 1/2 liter water bottle
  • 9 oz clear hard plastic tumbler
  • Boxes of small metal paperclips, 100 - 150
  • Paper towels
  • Sponges for clean-up
  • 12 oz clear plastic cup
  • 3 oz paper cup
  • Boxes of large metal paperclips
  • Boxes of plastic-coated paperclips
  • Bags of marbles
  • student journals and writing tools


  • Earth and Space Science
  • Physical Sciences
    • States of Matter
      • Liquids
    • Structure and Properties of Matter
      • Atomic Structure
  • The Nature of Science
    • The Scientific Process
      • Asking Questions
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

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


Components that are part of this resource:

Includes alignment to state and/or national standards:

This resource is part of:

Access Rights:

  • Free access


Source Collection

  • Science After School Consumer's Guide


  • All rights reserved, State of New Jersey, 2006

Funding Source:

  • No Child Left Behind Act of 2001