FILM TITLE:
ACTIVITY TITLE:
Type of Activity:
Age Group Orientation:
Number of
Participants :
Subject:
Discover Science – Entropy Engine
Crane without engine
Experiment
8years and above
2
The effect of temperature on the elasticity of rubber the work
Materials :
Rubber strip – rubber tube - Holder with base and holder – metal pierced ball 50 g
weight - Plastic container (2) - Hair Dryer (issued hot air) - Scissors - ruler - a
thermometer - a solid thread to tie the ball.
Procedure:
1- Is the rubber heated?
Put the rubber near your forehead or lips.
Stretch the rubber and touch it to your forehead immediately
Do you feel temperature change?
Now return the rubber strip to its original shape. Put it near your forehead or lips
directly.
Do you feel temperature change?
(heat can be measured by digital scale – laser technique)
2- the rubber does the work :
 install the holder and the mask on the base.
 Insert almost 10 cm thread through the ball’s hole. Connect it to make a
closed circle.
 Cut a length of elastic band 15 cm.
 Tight the ball with the rubber strip.
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Tight the rubber strip with the holder on a suitable height from the table
surface.
Shed hot air from a hair dryer on the rubber and observe closely what will
happen .
We measure the rubber length.
What do you think will happen? (expectations of the public can be collected
before carrying out the experiment).
Who is doing the work?
Explanation:
When we stretch the rubber (increases in length) its internal fibers will arrange
causing heat emission (low entropy). When the fibers re-interlock (it decreases in
length) Instead of arranging, and the rubber absorbs the heat (it has higher
Entropy).
What happens to a stretched rubber due to the added weight if it is heated? It is
expected that adding heat will help fibers to reconnect more tightly which will
shorten the length of rubber and pull of the weight upwards.
Preparation Time: 10 minutes
Activity Time: 10 minutes
Further Information / Source:
http://scifun.chem.wisc.edu/homeexpts/rubberband.html
http://www.physlink.com/education/askexperts/ae478.cfm
http://dahorner.faculty.noctrl.edu/CHM-PHY340/Lab/rubber_band.pdf
Activity suggested by: Palestinian Development Team - Ramallah - Palestine