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Observation Experiment on Solutions

Lab 1: at lab stations 1 and 2

Determine the relative solubility of the following solvents: water, rubbing alcohol, vegetable oil

Solvents: water, rubbing alcohol, vegetable oil

Solutes: sugar, cornstarch, salt

Other materials: laminated chart, stir rods

1. Place a small amount of each solute in the respective place on the chart.

2. One at a time, place three drops of each solvent in the respective place on the chart.

3. Stir the solute and solvent together

4. Make observations in the chart below. Include the terms: soluble and insoluble, polar and nonpolar.

5. Rinse off and dry chart and stir rods. Return all items to lab bench for next group.

| |Water |Rubbing alcohol |Vegetable oil |

|Sugar | | | |

|Cornstarch | | | |

|salt | | | |

Analysis Questions

1. Based upon the results of the solubility experiment, rank the three liquids from highest solubility to lowest solubility.

2. Based on your results, do you think that rubbing alcohol and cornstarch are polar or nonpolar?

3. How do you think the result would change if different solutes were used? For example, wax, animal fat and

Lab 2: at lab stations 3 and 4

➢ So, how do you get polar and nonpolar molecules to mix together?

1. Combine equal amounts (approximately 10ml) of oil and water in two small jars.

2. To one add one spoon of detergent.

3. Shake the jars and observe.

4. Measure how long it takes the oil and water to separate in each.

5. Observations, be specific

The better the detergent, the longer the oil and water stay as an emulsion.

emulsion: A suspension of small globules of one liquid in a second liquid with which the first will not mix

What happened? Detergents have a hydrophilic (water loving) head and a hydrophobic (oil attracting) tail.

Soap is made up of molecules which act like an oil on one end and like an alcohol on the other, so they are soluble in oils, in water, and in alcohol. 

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➢ CLEAN-UP:

1. Wash out jars, with soap and water, then dry with a clean paper towel.

2. Return all cleaned items to lab bench for next group

Analysis question

1. What might happen to your skin if you washed too often?

Lab 3: at lab stations 5 and 6

Background:

Polystyrene is a polymer ("poly" = many; "mer" = units) of thousands of styrene molecules linked together:

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Polystyrene is a clear, hard plastic. Air (or other “blowing agents”) can be blown through molten polystyrene as it is extruded, producing the light foamy material that we all know as "StyrofoamTM." StyrofoamTM is a very lightweight material because it is mostly air. In addition, the trapped air pockets make it a good heat insulator. Finally, the thin walls of the styrofoam bubbles make the material flexible enough that it is a good packing material. Styrofoam "packing peanuts" and cups are very common. However, they are not biodegradable.

[pic]

In recent years, concern for the environment has led to the development of biodegradable plastics, including biodegradable packing peanuts. These are made primarily of starch, which is a polymer of glucose. Starch packing peanuts are soluble in water (due to all the OH groups) but not soluble in acetone.

[pic]

➢ Test Styrofoam and packing peanuts in water and acetone.

1. Place a piece of Styrofoam and place in water, place another piece in acetone. Record observations.

2. Do the same thing with the degradable packing peanuts. Record observations.

3. Did the Styrofoam and packing peanuts truly dissolve? Explain.

➢ CLEAN-UP:

1. Wash out beakers, with soap and water, then dry with a clean paper towel.

2. Return all cleaned items to lab bench for next group

Analysis question

1. Coffee, tea, and soft-drink stains are generally removed in the wash, while stains from candle wax, salad dressing, and peanut butter require special treatment. EXPLAIN why.

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