Question

Data 1. What color did you get when you mixed iodine and starch? Remember to make your observation fairly quickly since the color will fade if you wait longer than about 5 minutes. 2. Do the experiment at the three different temperatures and record your observations of color change both inside and outside each baggie in the following two tables. Record your data using the following notation. - no color+ very small amount of purple/blue/black++ purple/blue/black spots+++ purple/blue/black throughout Inside the baggie 0 min. 5 min. 10 min. 15 min. 20 min. 25 min. 30 min.Cold Room temp. Warm/hot control Outside the baggie 0 min. 5 min. 10 min. 15 min. 20 min. 25 min. 30 min.Cold Room temp. Warm/hot control C. Questions 1. Why was there a color change when iodine is added to starch? 2. What was the purpose of the control?3. What did you learn/confirm from the color observation outside the baggies? 4. How did you keep the: 2-diffusion, revised 9/16/15 a. hot sample hot?b. cold sample cold? 5. What special conditions (if any) did you use when performing this experiment?6. What molecule is diffusing? What is the physical evidence for your conclusion? 7. Which temperature shows the fastest diffusion rate? Which temperature shows the slowest diffusion rate? Does thismake sense to you based on what you know about the effect of temperature on the movement of molecules? Explain your answer.8. How could this experiment be improved (To make it scientifically better)? Remember that all experiments can beimproved.

Answer 1

1. Why was there a color change when iodine is added to starch?

Answer: Starch consists of two types of molecules, amylose alpha which is a soluble starch and amylopectin. When starch is mixed with iodine in water, an intensely blue colored starch iodine complex is formed. Apparently, the iodine gets stuck in the coils of beta amylose molecules.

2. What was the purpose of the control?

The purpose of a control is to show what would normally happen and compare it with what happens when you change the independent variable. This shows that if the independent variable is really responsible for your observations or not.

3. What did you learn/confirm from the color observation outside the baggies?

We can learn from the color observations outside the baggies that the color intensity of starch-iodine complex decreases with increasing temperature. Thus, at cold temperature, dark blue color can be observed, at room temperature, blue color can be observed and at warm temperature, faint blue color can be observed. As the time increases, the color intensity gets decreased.

4. How did you keep the: 2-diffusion, revised 9/16/15 a. hot sample hot?b. cold sample cold?

For the diffusion of hot sample hot, we should fill the hot sample in a tea bag and keep it in hot water in a beaker whereas to maintain the diffusion of cold sample cold, we should place the cold sample in tea bag and should keep in the cold water or solution in a beaker to maintain required temperatures.

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