Rubber hand

An effective way of explaining molecular behaviour to students and the public alike is by

relatability and easily recognizable occurrences. Human body functions are relatable and

accessible.

In the case of rubber band retraction in the presence of increased temperature we have the hand

staying clenched, after being squeezed tightly for a few seconds, you have an example and

relatable occurrence.

By th students squeezing the hand the forearm muscle titin is activated by electrical impulses the

retention of the hand's position is the current line staying open. In an ideal rubber band as an

elastomer ( a bundle of disorganized copolymer fibers until stretched) the relation between

restoring force or retracting (f) , length φ (L), temperature (T) is linear as shown in the follow

equation

f= T φ (L)

Ask the students to squeeze their hands for a few seconds as shown in the picture below

The clenching mimics the the disorder of copolymer fibers in rubber when heated. After a few

seconds ask the students to open their hands as shown below

Their forearm muscles will resists slowly

opening this mimics the cooling and slow return to ambient temperature of rubber.

Recap

• Hand clench is analog for retraction of rubber

• Electrical impulse analog for heat that causes retraction

• Opening of hand analog for rubber's return to ambient temperature