Carbon Molecules Lab Activity (Chapter 2.3) clone

By Kathy Egbert

Last updated about 6 years ago

21 Questions

How do we clean up oil spills in the ocean?

Some of the methods used to clean up oil spills are:

An oleophilic surfactant means that it "loves" oil and adheres to it.

Demonstration 1: Polymers - Use in environmental clean-up of oil

When a polymer comes in contact with a liquid hydrocarbon (crude oil, diesel fuel, and gasoline) the free hydrocarbons bond to the polymer forming a solid mass. The hydrophobic properties of the polymer cause it to float on water, but the density of the polymer is great enough to allow it to sink through the hydrocarbon and maximize the bonding potential. There is no need for mixing since the polymer bonds to the free hydrocarbons automatically and encapsulates the liquid hydrocarbons in about five minutes.

After the demonstration, you will have an opportunity to feel the oil-saturated polymer. Describe how the polymer feels? Describe its odor.

Demonstration 2: Polymers - Use in Commercial Processes

<> Notice how the sheets of polymers are stretched as they go over rollers. Using less packaging materials cuts the cost to the manufacturer and increases profits.

Polymers are long chains of molecules. Their natural state is similar to a knotted up string. These polymers can be heated and stretched out to make flat materials used for packaging. The high heat of the process locks the molecules into their “stretched out” state. If heat is used to break these “stretched out” bonds, then the material returns to its original size. Packaging materials are often lined with other materials such as aluminum and paint—these layers are still bound together in the shape of the object. So, although the polymer chains bunch back into their natural shape, the overall shape of the object is maintained.

The original potato chip bag is smooth and forms an even rectangular shape.

After the heat treatment, the potato chip bag is wrinkled, hard and brittle, and less than a fourth of its original size.

The layer of the potato chip bag that has the advertising print on it for the product is still readable after the heat treatment.

Experiment 3: Water Absorbing Polymer Sodium Polyacrylate

Some molecules are very large and others are small. A single molecule is called a monomer – mono means one and mer is the suffix for unit. So, a monomer is a molecule of a single unit. If the prefix poly means many, then a polymer is a large molecule made up of many smaller units, which are joined together. Some polymers are made up of millions of monomers.

What can a polymer do? Polymers play a large role in our everyday lives. Synthetic polymers have a multitude of uses from something as simple as a Styrofoam coffee cups to plastics, adhesives, fabrics, paints, rubber, polyester, gelatin, or even a life-saving artificial heart valve. The world as we know it today could not exist without these long chains of molecules called polymers.

The superabsorbent diaper polymer, sodium polyacrylate, absorbs water by means of osmosis, the movement of water molecules through a semi-permeable membrane. In this instance, the polymer network acts like a semi-permeable membrane, letting only molecules of water pass through the membrane-like structure of the polymer. Larger molecules of other substances are stopped by the semi-permeable membrane. When the polymer comes in contact with water, the water molecules migrate from the outside of the polymer to the inside, causing the polymer to swell.

What causes the water molecules to move inside the polymer? Water will rush into the polymer if the sodium ion concentration is greater inside the polymer than outside in the water. In the process of making the polymer in the laboratory, sodium ions, just like those found in table salt are chemically bonded to part of the polymer molecule. So, in pure water the sodium ion concentration is naturally greater inside the polymer than outside in the water and water rushes in trying to equilibrate the sodium ion concentration inside and outside the polymer. Although the polymer network has an elastic-like quality, it can only stretch so far. The amount of water that the polymer can absorb is determined by the elastic strength of the polymer.

Diaper lining acts like a semi-permeable membrane, so urine is absorbed by the
polymer, keeping the child's skin dry

Instructions (1 out of 5)

1. Pour water into your beaker and measure out 100 ml
2. The next step requires you to work with your partner.

Open the Ziploc bag containing the premeasured polymer and hold it open so your partner can pour the water into the bag.
Be careful not to drop the bag. Reseal the bag.
Massage the bag gently to make sure all the polymer is dissolved.

Which of the following best describes the consistency of the products in the Ziplock bag?

Instructions continued (2 out of 5)

3. Use the beaker to measure out an additional 100 ml of water

Based on what you know about polymers, predict whether the polymer can hold an additional 100 ml of water.

Instructions continued (3 out of 5)

4. Again with the help of your partner, open the Ziplock bag and pour the additional 100 ml of water into the bag.
5. Close the bag and reseal it.
6. Massage the bag again to be sure to mix up the water with the polymer solution.
7. Remember from the background material that salt (sodium ions) is attached to the polymer to help draw the water into the polymer through the membrane on the diaper. This works well so long as the diaper is exposed to regular water.

Using this information about how salt is attached to the polymer, predict what will happen when you add salt to the mixture causing a change in the concentration gradient.

Instructions continued (4 out of 5)

8. With the help of your partner, open the Ziplock bag and add the premeasured salt into the polymer solution.
9. Close the Ziplock bag and massage it.
10. Observe

The polymer mixture changed from its semi-solid state back to a more liquid state.

Instructions continued (5 out of 5) - Clean up

Place the empty salt Ziplock bag in the tub marked for the plastic bags so it can be reused. If you got the salt bag wet, then throw it away in the trash can.
Take the Ziplock bag with the polymer mixture to the tub marked waste. Put the closed Ziplock bag in the tub.
Be sure your table is clean and any spills are wiped up.

After observing what happened when salt was added to the polymer, theorize about what might happen to a urine-filled baby's diaper if left on an ocean beach where it would get wet.

Ocean water is very salty.

When the salt was added and the polymer solution became more runny, chemical bonds must have been broken in the reaction.

Demonstration & Participation 4: Cell membranes are composed of a bi-layer of
phospholipids with a polar head and a non-polar tail

Cell membranes surround a cell and physically separates the inside materials from the outside environment. To do this, the cell membrane has to have unique properties and this occurs because it has a phospholipid bi-layer—one end hydrophobic (not liking water, non-polar) and one end hydrophilic (liking water, polar).

The polymer used in the baby diaper was hydrophilic (attracted to water).
Hydrophobic molecules can also be attached to polymers making them hydrophobic
(repels water).

Instructions
You will be provided with a cup of water which is on top of a cup with some sand
Pour the sand into the cup containing the water
Observe how the sand feels in the water
Now separate the sand from the water by pouring the water off the sand from one cup to the next
Put the two cups back together like you received them: the water cup on top and the sand cup underneath
Return the cups back to the tray so they are ready for the next class

Describe how the sand felt out of the water.

Describe how the sand felt in the water.

Demonstration 5: Properties of Lipids

Lipids are large molecules and have the ability to stretch and change shape.

Using your chromebook and open a stopwatch/timer app (no cell phones today)

Predict how long it will take for the bubble to break.

What was the actual time it took for the bubble to break?

Experiment 6: Properties of Lipids (Fats) and Proteins

Milk is mostly water, but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk).

You are going to observe how the weak bonds that hold proteins in solution are altered; how fats cluster to form micelle causing motion; and how lipids break the cohesive bonds in water that create surface tension.

You are also going to compare this reaction in whole milk (abt 12% fat) and skim milk (abt 0 to 2% fat).

Create a hypothesis before you begin this experiment. If fats break bonds, then ...............fat content will make the reaction occur .........

Instructions

You and your partner need to prepare your plates so that you can run your test at the same time because you will be comparing which plate has the faster reaction and whether the reaction causes more movement or not.

1. There are two plastic plates in your materials tub. Each pair of partners: one will put whole milk on their plate and one will put the skim milk on their plate.

2. Go to the location where the milk is set-up. Use the beakers by the milk to measure out 40 ml

3. Go back to your table and pour your milk onto your plastic plate. Return the beaker to the front so someone else can use it. (Be careful not to mix up the beakers with the other milk product)

4. After you and your partner have your milk on your plates, mentally divide the plate in four quadrants. Take turns using the food coloring to place four drops on your plate (one of each of the four colors) in the four quadrants - leaving the middle of the plate without any food coloring. See picture that follows:

Setting up the Control - we need to know if the reaction is occurring due to the
adhesive properties of water that create surface tension or if the reaction is
caused by the interaction of lipids (fats) and proteins in the milk

Each of you take one dry Q-tip and place one end in the center of your plate. Observe.

There was no significant movement when the dry Q-tip was placed in the center of the plate of milk.

Be sure that you and your partner start the next step at the same time

1. Plan to observe whether you think one plate reacted faster than the other; and also plan to observe if there is more movement in the whole milk verses the skim milk

2. Take the same Q-tip that you used for the control and dip the opposite end in the soap provided in your materials tub. You don't need much but make sure the tip has absorbed some soap.

3. Be sure that you and your partner do the next step together - at the same time each of you place your Q-tip with the soap end into the middle of your plate of milk

4. Observe.

Because we had a control that showed there was no movement when the dry Q-tip broke the surface tension of the milk, we can claim that the movement was caused by the lipids (fats) breaking water and protein bonds in the milk.

Clean-up - No one leaves until everyone in the class room has completed cleaning
up

Pour the contents of your plate (the milk and food coloring) in the appropriate tub marked for disposal
Put your dirty plate in the tub marked for the dirty plates (do not wash them in the wash station or the sink)
Discard the Q-tip in the waste basket
Be sure the dish soap lid is securely placed on the bottle
Wipe down your table and make sure you have cleaned up all spills