Energy Clues in the Dairy Cooling Room

Getting the Dairy Room Ready

Before visitors arrived at a dairy farm, Rosa's class explored a clean room where milk containers are cooled. The milk equipment stayed off during the visit. Farm guide Ellis helped the class investigate with a handbell, a window shade, sealed water bottles, and a battery-powered fan. The bottles held water, not milk. An adult handled the cold pack, and the electrical equipment stayed on a separate, dry table.

Ellis rang the handbell behind a tall wooden divider. Rosa stood three meters away. She could not see the bell, but she heard each ring. When Ellis stopped ringing, the ringing sound faded away. Next, Ellis moved the bell beside the divider. Rosa could now see and hear it. Her position and the strength of the bell ringing stayed the same.

Sunlight passed through a clear window onto a white card two meters inside the room. Ellis lowered a thick shade, and the bright patch on the card disappeared. Raising the shade brought the patch back. The window remained closed, and the card stayed in place. During this short test, the sky stayed clear and the room's electric lights stayed off.

For a cooling test, Ellis filled two matching sealed bottles with equal amounts of water at 26°C. He wrapped a cold pack around one bottle and left the other without a pack. Both stood on the same table in 26°C air. The class recorded the water temperatures every five minutes for fifteen minutes. The bottle without a pack stayed at 26°C. The graph shows the bottle with the pack. Ellis checked that the pack stayed below 14°C. No water leaked, and the pack's contents stayed sealed inside it.

On the dry table, a battery stood one meter from a small fan. Wires and a switch connected them. Closing the switch made the fan blades spin. Opening it made the blades slow to a stop. Closing it again restarted the fan. The class kept the battery, fan, and wires in the same positions.