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I have to do a chemistry self planned lab, and the theme (topic) is to: "Investigate a...

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idrajit | Student, Grade 12 | (Level 1) Honors

Posted September 4, 2013 at 1:02 PM via web

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I have to do a chemistry self planned lab, and the theme (topic) is to: "Investigate a Factor Affecting Rate."

So basically I would like to know any ideas of chemicals that I could use for my reaction to, say see how a difference in temperature (or concentration, etc.) would change the rate, and how the rate would be measured. If possible, also a list of materials needed and basic procedures would be very helpful.

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ncchemist | eNotes Employee

Posted September 7, 2013 at 1:10 AM (Answer #1)

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I'm not sure exactly what kinds of materials and chemicals you have access to for your lab experiment but one suggestion I have that utilizes very basic chemicals that you could readily purchase would be the reaction of iodine with the fats in different cooking oils. 

The chemical iodine (I2) has a deep purple color and can be purchased as a solution in solvent from any drugstore.  Iodine reacts with the fatty acids in cooking oils.  These fatty acids have mostly carbon carbon single bonds but they also have some carbon carbon double bonds as well depending on the saturation level of the oil (saturated fats, monounsaturated fats, polyunsaturated fats, etc.).  Iodine will reaction with the double bonds in unsaturated fats to produce colorless compounds.  So you can slowly add the purple iodine to the oil and mix it up and the initial color will disappear as the iodine reacts with the oil.  When all of the double bonds have been reacted, the excess iodine will remain and the purple color will stay.

You need to tailor this reaction to factors affecting reaction rate.  Two factors to measure are concentration and temperature.  Select two different oils.  I suggest peanut oil and canola oil.  Peanut oil has more saturated fats than canola oil does.  That means that canola oil has a higher concentration of carbon carbon double bonds than peanut oil does.  So measure out an equal weight of both oils and see which one consumes a few drops of iodine faster (make sure you use an equal number of drops for each oil).  Measure the rate by the time in takes in seconds for the initial color to disappear.  The canola oil has a higher concentration of double bonds so it should have a faster rate of reaction and therefore the color should disappear faster than for peanut oil.

Similarly, you can measure the affect of temperature on the reaction.  Choose one kind of oil and measure out two equal portions of it.  Heat one cup of oil on the stove or microwave and cool the other cup of oil in the refrigerator.  Now add an equal amount of iodine to each cup of oil and see which one takes the longer to lose its color (again, measure the reaction rate by measuring the time in seconds).  The hotter oil should react faster than the colder oil, thereby losing its color faster.

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