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.