Archery Field: Inside Two Ice Packs

A Demonstration at the Equipment Table

At an archery field, equipment helper Tessa prepares a science demonstration about two cooling packs. An adult makes both packs from equal amounts of water, using matching clear, waterproof bags. Pack A contains one large piece of ice. Pack B contains several small pieces of ice. The adult handles the ice and seals the bags. The demonstration happens at the equipment table, away from the practice area. Students observe the packs without opening them.

Tessa changes the size of the visible ice pieces. She keeps the bag type, starting amount of water, and table surface the same. Both packs start at the same freezer temperature. She places them side by side indoors, away from sunlight. She starts a timer and records how long each pack takes to become completely liquid. She checks the seals during the test and finds no leaks. The graph shows her results from this one comparison.

Before much melting occurs, Tessa gently tips each bag. The ice pieces slide, but each piece keeps its own shape. Later, liquid gathers around the shrinking pieces. The liquid moves toward the lower side when she tips a bag. After the ice has melted, she lays each bag flat and then stands it upright with support. The water spreads into a shallow layer in the flat bag and gathers into a deeper pool in the upright bag. The clear water remains visible inside both bags.

The students can see ice pieces, water surfaces, and bag outlines. They cannot see individual water particles with their eyes, even in the clear liquid. Scientists use models to explain matter at this much smaller scale. For their drawings, students will use dots as symbols for water particles. Each dot represents a large group of particles, not one actual particle. The dots are enlarged symbols, not actual-size pictures. A model should include a key and explain both the visible observations and the matter that eyes cannot resolve. The students must decide which proposed drawings fit the evidence.