Rubber is entropy-elastic that means its elasticity is driven by entropy. Entropy is a measure for disorder and increases with increasing temperature.[br][br]Rubber consists of long chain molecules that form a network. In its relaxed form a rubber band is in a highly disordered internal state. Upon stretching the long chain molecule of the rubber band are aligned and the disorder decreases. What will happen if a stretched rubber band is heated?

Rubber band, cut open [br]empty plastic bottle or glas bottle with lid[br]water[br]hair dryer[br]door handle/window handle[br]

1 Cut a rubberband to obtain a straight piece of rubber and tie a loop at one end [br][br]2 Fill a plastic bottle/plastic beaker with tap water and clamp the open end of the rubber band under the lid[br][br]3 Slide the rubber loop around a door handle, the water filled bottle/beaker should stretch the rubber band without rupturing.[br][br]HINT: If necessary, adjust the water level in the bottle/beaker to stretch the rubber band under its weight[br][br]4 Place a removable mark at the wall/door to see where the top of the bottle is with the stretched rubber band.[br][br]5 Plug in a hairdryer, turn it on and heat the rubber band by moving the dryer up and down the rubber band.[br][br]What do you observe? Does the rubber band get (1) longer/ (2) shorter? Type the number of the correct answer into the box below.[br][br][br][br]