Surface Area to Volume Ratio Experiment
Introduction: Surface Area to Volume Ratio is important in body
systems, particularly the digestive and respiratory systems. A high
surface area to volume ratio means that substances can diffuse in or
out of a cell quickly. This experiment provides a model for
understanding why the small intestine contains villi or why the alveoli
in lungs are so numerous and tiny. The agar used in this experiment is infused with phenolphthalein
indicator and sodium hydroxide so that it appears pink. As the acid diffuses into the agar, the
indicator changes from pink to clear.
Materials
Agar prisms of the same volume but different dimensions eg 2 x 2 x 2 cm, 2 x 4 x 1 cm
Knife and cutting board
Clear Ruler
200ml beaker
100ml sulfuric acid
Stopwatch
Method
Wearing gloves, cut the cubes to shape
Place them in the acid at the same time
Time how long each piece of agar takes to go completely clear
Analysis of results
Calculate the surface area of your two pieces of agar
Calculate the surface area to volume ratio
Draw a graph comparing surface area to volume ratio and the time taken
Discussion
Provide details of three examples from human body systems where surface area to volume ratio is
important.