Slithering Sweet Science Introduction Molecules tend to move from areas of high concentrations to areas of low concentrations and are always in constant motion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. When water molecules diffuse through a selectively permeable membrane it is known as osmosis. Selectively permeable means that some molecules can transport through the membrane, but others cannot. The molecules move across the membrane until equilibrium is reached and both areas have equal concentration. The candy, Gummi Worms are primarily made up of gelatin, sugar, and starch. The purpose of this experiment is to observe the percent change in mass of gummi worms exposed to various concentrations of sugar water.
Hypothesis
If the concentration of sugar in the surrounding solution is sufficiently increased, the percent change in mass of the gummi worm will be negative, meaning the mass of the gummi worm will decrease. Likewise, if the sugar concentration is sufficiently decreased, the percent change in mass will be positive, meaning the mass of the gummi worm will increase.
Materials: * Four 200 mL beakers * Gummi worms * Sugar * Distilled water * Kitchen scale and weighing trays * Glass stirring rod * Masking tape and marker for labeling * Sieve * Scoopula
Procedure 1. Prepare four 200 mL beakers by labeling them with the masking tape and marker. There should be a beaker labeled for each of the following concentrations: 0%, 5%, 10%, 20%. 2. In the beakers, calculate and mix the respective concentrations of sugar and water mixtures. Do this by multiplying the desired concentration percentage by 200 to find the desired amount of sugar. Using the scoopula, weighing tray, and scale, measure the correct amount of sugar for each beaker. Then, fill the beaker up to 200 mL with water and stir using the glass stirring rod. 3. Find and record the mass of each of five gummi worms, (be sure to zero the scale if using a weighing tray,) place one in each of the beakers, and leave one left out. The gummi worms in the concentrations will act as experimental groups while the gummi worm left out acts as a control group. 4. Leave them to sit overnight. 5. Carefully pour the sugar water out of each of the beakers over a sieve to catch the gummi worm and pat dry with a paper towel. 6. Measure and record the new mass of each of the gummi worms and calculate the percent change in mass using the following calculations:
% Change in mass = (Final mass - Initial mass)/ Initial mass × 100
The concentration of the sugar water acts as the independent variable; while the percent change in mass acts as the dependent variable.
Analysis 1. What happened to the mass of the gummi worms as the concentration of sugar water increased? Using the terms solute and net movement, explain the reasoning behind the percent change in mass. 2. Predict what changes would occur in an 80% concentration of sugar solution given that the concentration of sugar in gummy worms is less than 80%. 3. Provide calculations used in finding the amount of sugar to use in each of the varying concentrations. 4. Provide calculations used in finding the percent change in mass for each of the four concentrations. 5. What was the average percent change in mass of all four experimental groups? Provide calculations to support your answer.
Answers
1. This phenomenon is due to the concentration of solute in the gummi worm compared to the surrounding solution. Due to the laws of osmosis, a higher surrounding concentration caused less net movement of water across the semipermeable membrane before equilibrium was reached. 2. When the concentration of solute in a surrounding solution is greater than that of the gummi worm, water will have a net movement flowing out of the gummi worm rather than in. This will cause a quantitative result of a negative percent change in mass and a qualitative result of visibly decreased size in the gummi worm. 3. Given that 1 mL of H₂O=1 g C₆H₁₂O₆ 0%- 200mL X 0% 200mL X 0.00=0 g C₆H₁₂O₆ 5%- 200mL X 5% 200 mL X 0.05= 10 g C₆H₁₂O₆ 10%- 200 mL X 10% 200 mL X 0.1= 20 g C₆H₁₂O₆ 20%- 200 mL X 20% 200 mL X 0.2= 40 g C₆H₁₂O₆ 4. Given that %ΔMass= (Final mass - Initial mass)/ Initial mass × 100 0% - (28.182g - 7.430g)/ 7.430g × 100= 279.30% 5% - (7.817g - 27.723g)/ 27.723g × 100= 254.65% 10% - (19.776g - 7.894g)/ 7.894g × 100= 150.52% 20% - (18.501g - 7.882g)/ 7.882g × 100= 134.72% 5. Given that Average= (sum of values)/(# of values)
Average=(279.30+254.65+150.52+134.72)/4=204.80%
Conclusion After analyzing the results of this experiment, one can come to the conclusion that as percent concentration increases, percent change in mass decreases. This phenomenon is due to the concentration of solute in the gummi worm compared to the surrounding solution. Due to the laws of osmosis, a higher surrounding concentration caused less net movement of water across the semipermeable membrane before equilibrium was reached. These findings supported the hypothesis even though a negative percent change in mass was never recorded. One can deduce based on the patterns of change that, if the pattern continues, a negative percent change in mass will be reached.
Works Cited
"Diffusion." And Osmosis. Department of Physics and Astronomy. Web. 4 Feb. 2015. <http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html>.
Melgaard, Katie. "Investigating Osmosis Using Water and Gummy Bears." MnSTEP Activity Mini-collection. Hamline University Grad School of Education. Web. 4 Feb. 2015. <http://serc.carleton.edu/sp/mnstep/activities/26990.html>.
"Steps of the Scientific Method." Steps of the Scientific Method. Web. 4 Feb. 2015.
<http://www.sciencebuddies.org/science-fair-projects/project_scientific_method.shtml>.
