Unlike waves in a string which propagate without spreading, heat flows by diffusion so that a heat pulse will spread rapidly as it travels. Notice which metal conducts more quickly. Place one end of the metal into hot water until the colors have propagated about half way up the liquid crystal. Remove the end from the hot water and place it in the cold water. Notice how the colors allow you to follow the temperature changes in the metal.
Heat flows from the metal into the cold water.
The color bands produced by the hot and cold waters spread and merge. Continue to alternate the end of the metal between hot and cold baths. Notice that the color starts out as pulses which then spread and blends. As you alternate and time progresses, the heat pulse takes longer and longer to travel the same distance. This behavior indicates that heat conducts by diffusion.