Fragile Waters

Time: 45 minutes

Materials (per group):

Newspaper to cover workspace / Small cups for oil and water / Small rocks or seashells / Feathers / Faux fur
Motor oil* / Small brush / Shallow pan / Dawn detergent / Paper towels

*If the teacher is opposed to motor oil, vegetable oil can be used. This must be specified.

Materials (per class):

1 glass jar / Gallon Ziplock for dirty objects / Plastic Pipet / Plastic Spoons / Container for water

Read/paraphrase this:

In the icy, clear Gulf of Alaska waters live 10,000 to 15,000 sea otters. The rocky coast and plentiful shellfish make this an ideal habitat for otters. Thousands of birds, fish, whales, and other marine life also make their home here. Unfortunately, on March 24, 1989, shortly after midnight, an environmental catastrophe occurred. A 306-meter oil tanker, the Exxon Valdez, slammed into a rock reef which ripped open the ship’s steel hull.

The crash released over11 million gallons of crude oil into the Gulf of Alaska in less than 5 hours. The oil poured out so fast and with such force that a wave of oil 1 yard high formed on the surface of the water. In less than two days the spill had spread 30 miles on calm water. On the 4th day, a storm moved in with winds up to 60 miles an hour. The oil continued to spread and by the 19th day it was 250 miles down the coast. By the 56th day the oil had traveled 465 miles southward.

One month later, oil was found all along the beautiful fragile coastline, at distances of more than 1200miles from the original spill. Because sea otters rely on clean and dry fur to keep warm, the oil coating their fur was life-threatening. Scientist estimate 3,000 sea otters died.

Directions:

Part I (Demonstration only)

1.Put equal parts of water and oil in the glass jar (⅓cup each). Where is the oil in relation to the water?

2.Mix carefully (close lid tightly and tilt upside down, then back). Now observe the oil in relation to the water again. Why do you think the oil is sitting on top of the water?

3.Now place a spoon on a folded-over paper towel. Use the pipet to fill the spoon with oil. When it looks full, add more oil one drop at a time. Have the students count how many drops it takes to make the oil spill over.

Part II (Main Activity)

4.Instruct students to form groups of 4. Have one student come up and gather the materials that will be tested: a rock, a sea shell, two feather, some faux fur fabric.

5.Use the shallow pan of water to test each item to see which ones will float. Float only one feather (keep one dry for later). Discuss which items float in water and which items don’t float.

6.Remove all items from water and dry with a paper towel.

7.Discuss with the students which items would be most damaged by oil in the event of an oil spill.

8.Place items on a pile of paper towels. Use brush to apply motor oil from the cup to all items except the dry feather. Did the oil soak into the samples? If so, which ones?

9.Place one oiled feather and one dry feather in the pan of water. Compare how they float. How do the students think an oil spill affects birds?

10.Fill one cup with a Dawn and water mixture and have students try to clean the objects by rubbing them with their hands in the soapy water. The may want to pour the soapy water into the tray.

11.Have the students compare how well they were able to clean the objects. What does this tell us about items in an oil spill?

Have students help clean up at the end of the activity. Water should be poured down the sink. Oil may also be poured down the drain, but make sure to flush it with a bit of Dawn and lots of hot water. Feathers and faux fur should be thrown out, and other test objects, spoons, pipets, etc, need to be sealed into the provided Ziplock bag. Empty the glass jar and make sure its lid is sealed tightly. All plastic cups should be rinsed out and DRIED before being put back in the kit.

Tell students that, just like an oil spill hurts the environment, oil can damage our personal supplies in everyday life.

Discussion:

Q: What do you think should be done to avoid oil spills?

Q: What properties of oil make it hard to clean up? Think of as many words as you can to describe the properties of the oil you tested.

Q: Why don’t water and oil mix?

A: The reason why oil and water don’t mix has to do with the kind of molecules from which each are made. Water molecules are polar; that is, they have a minute negative charge on oxygen part of the molecule and minute positive change on the hydrogen parts of the molecule.

This means that water molecules will cling together, because positive and negative charges attract each other. So weak bonds are formed between water molecules.

Oils, on the other hand, are made up of molecules which are non-polar (They carry no positive or negative charge). They are sometimes called hydrophobic (meaning water hating). This hydrophobic property causes the molecules to clump together into globules when added to water. So the oil will not mix with water.

The reason why oil floats on the surface of the water is to do with its density. A given volume of oil has less mass than the same volume of water. This means it has less density than water and so floats on top. This is Archimedes principle and is expressed by density = mass/ volume. You can find out more about density in your physics and science books.

Q: We have established that oil and water don’t mix. What are the advantages and disadvantages of this in an oil spill?