Uploaded December 2025 | Updated September 2026, 2 weeks ago
#heattransfer #conduction #energy #ngscience @NGScience
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Watch conduction in action!
Here we have a retort stand with a metal rod attached. Thumb tacks are attached to the rod using a small piece of wax. Three thumb tacks are placed at even intervals along the rod.
At room temperature, the thermal energy of the rod, and therefore its temperature, is evenly spread from one end to the other.
Let's increase the thermal energy of the rod by placing a burner at one end.
The movement of thermal energy is called heat, and heat always moves from hot to cold. As the rod is heated, thermal energy transfers along the metal through a process called conduction.
Here's what happens at the molecular level: the metal atoms near the burner start vibrating more vigorously as they absorb heat energy. These rapidly vibrating atoms bump into their neighboring atoms, transferring some of their kinetic energy. Those atoms then bump into their neighbors, and so on down the line.
This chain reaction of collisions causes thermal energy to spread along the rod from the hot end toward the cold end.
As the heat conducts along the rod, it reaches each piece of wax in sequence. When the wax absorbs enough thermal energy, its temperature rises to its melting point. The wax softens, loses its grip on the rod, and the thumb tack falls away.
The thumb tack closest to the burner falls first, followed by the middle one, and finally the one farthest from the heat source. This demonstrates that heat moves progressively from the hot end to the cold end through the metal rod— proving evidence that thermal energy always flows from regions of higher temperature to regions of lower temperature.
#heattransfer #conduction #energy #ngscience @NGScience
ngscience.com
Watch conduction in action!
Here we have a retort stand with a metal rod attached. Thumb tacks are attached to the rod using a small piece of wax. Three thumb tacks are placed at even intervals along the rod.
At room temperature, the thermal energy of the rod, and therefore its temperature, is evenly spread from one end to the other.
Let's increase the thermal energy of the rod by placing a burner at one end.
The movement of thermal energy is called heat, and heat always moves from hot to cold. As the rod is heated, thermal energy transfers along the metal through a process called conduction.
Here's what happens at the molecular level: the metal atoms near the burner start vibrating more vigorously as they absorb heat energy. These rapidly vibrating atoms bump into their neighboring atoms, transferring some of their kinetic energy. Those atoms then bump into their neighbors, and so on down the line.
This chain reaction of collisions causes thermal energy to spread along the rod from the hot end toward the cold end.
As the heat conducts along the rod, it reaches each piece of wax in sequence. When the wax absorbs enough thermal energy, its temperature rises to its melting point. The wax softens, loses its grip on the rod, and the thumb tack falls away.
The thumb tack closest to the burner falls first, followed by the middle one, and finally the one farthest from the heat source. This demonstrates that heat moves progressively from the hot end to the cold end through the metal rod— proving evidence that thermal energy always flows from regions of higher temperature to regions of lower temperature.
