Passage II
Seven 4 g mixtures of glycerol and agar were prepared, each having a different percent glycerol by mass. A plastic film was made from each mixture; all the films were rectangular and had the same dimensions.
Each film was clamped and stretched (see Figure 1) at 25°C until it broke.
Three properties of the film were determined:
• Tensile stress, the force applied per unit area of the film as the film broke
• Percent elongation, given by:
• Elastic modulus, a measure of the rigidity of the film
The results for all 7 films are shown in Figures 2 and 3.
Figures adapted from Eugene S. Stevens et al., "Polymer-Plastics Experiments for the Chemistry Curriculum." @2006by Division of Chemical Education, lnc., American Chemical Society.
8. Suppose a film made from a mixture that was 55% glycerol by mass had been tested. Based on Figure 2, the tensile stress of the film would most likely have been:
Your Answer is
Correct Answer is F
Explanation
Find the solid line in figure 2, and according to the trend of changing the line, it can be inferred that when percent glycerol by mass=55, the tensile stress is about 10, less than 13