Find out more about oil spill cleanup with the science experiments in this article!
First, some background info on oil and water…
There have been many oil spills over the years, such as the Gulf oil spill in the U.S. that happened in April 2010, when there was an accident at a drilling rig in the Gulf of Mexico. A spill like this that is close to land causes many problems for the environment and makes it difficult to clean up. As little as three gallons of oil can spread to make a slick mess covering one acre of the ocean’s surface. With the Gulf oil spill, it’s estimated that 200,000 gallons a day have spilled into the ocean as scientists work to stop the leak and clean up.
Oil spills like this are very damaging, but they aren’t the only source of oil that is polluting our waters. Rain washes particles from air pollution into the ocean. Natural seeps from the ocean bottom also occur every year. And one of the biggest sources of oil polluting the ocean is thought to be from the oil people put down their drains every day, as well as the runoff from parking lots. So, cleaning up the ocean is an important issue, not just because of recent oil spills.
Oil and water don’t mix — as you might already know. You also know that oil is sticky and greasy. This makes it hard to clean up. Let’s take a look at the chemical properties of oil and water to see why.
Each water molecule is made of two hydrogen atoms and one oxygen atom — H2O. When the two hydrogen atoms bond with the oxygen, they attach to the top of the molecule rather like Mickey Mouse ears. This molecular structure gives the water molecule polarity, or a lopsided electrical charge that attracts other atoms. The end of the molecule with the two hydrogen atoms is positively charged. The other end, with the oxygen, is negatively charged. Just like in a magnet, where north poles are attracted to south poles (“opposites attract”), the positive end of the water molecule will connect with the negative end of other molecules. Because of their polarity, water molecules are strongly attracted to one another.
What happens when oil and water are put together? The two liquids won’t mix. Oil is non-polar, meaning its molecules are balanced, with equal sharing of electrical particles, rather than one negative and one positive end. No matter how much you stir it, a mix of oil and water won’t come together, because the molecules can’t connect.
Oil is made of more complex molecules, containing carbon and hydrogen. Oil molecules are non-polar, meaning they don’t stick together like water molecules do. Oil is thick and heavy, yet its molecules are spread farther apart, lowering the density. Because it has a lower density, oil floats on water’s surface. Oil is also slippery — it doesn’t stick together like the polar molecules of water.
Experiment 1 – What happens when oil is added to water?
You know that water and oil don’t mix. Take a look at exactly how they react to each other and find out what happens to create an oil slick.
- Fill a clear plastic container a little over halfway up with water.
- Pour a few drops of cooking oil into the water, watching what happens when you start pouring very slowly, then pour quickly.
The oil always floats to the top of the water in the container. Even if you were to release it at the bottom, it would float up. If you pour slowly, the oil will stick together, making a big puddle. If you pour more quickly, the oil breaks into droplets, or smaller puddles. If you look closely, you can see tiny drops or particles of oil that are floating on the surface. All of these traces of oil — big and small — make an oil slick. Sometimes the oil is spread extremely thin, and in other spots there is a messy oil puddle. An oil slick is created when a lot of oil is released, so it floats up to the surface and spreads over a large area. In the ocean, waves and the wind spread the oil around even more.
Experiment 2 – Oil cleanup using absorbents
Reuse the container of water and oil from the last experiment. Find some materials around your house or school that have absorbent properties and could help soak up the oil to clean up the oil slick. Some examples: cotton balls, laundry lint, a paper towel folded into strips, and makeup remover pads or sponges. Make sure you choose something small and light.
- Place one of the absorbent items into the container of water, moving it around to soak up the spill.
- Try containing the oil by blocking off a small area with several pieces of the absorbent material. Can you make a square around the spill, without any oil escaping?
- Try this project again using one of the other absorbents. (You made need to add more oil to the water to create more slicks.)
- Once the majority of oil is soaked up, throw away the absorbent pads and any other materials you tried and then pour the water down the sink.
In real life, floating objects, sort of like a big sock, are carried into the ocean and then pushed off the side of a boat to help soak up oil spills. These socks (called booms) are filled with absorbent material that can soak up a lot, yet are also lightweight. You created a type of mini boom in this experiment. It works to clean up water by soaking up the messy spill once it gets close to a drop of oil. These booms are very effective, but the difficulty is in controlling them so that they go where the oil is. Was it hard to contain the oil to a small area in this experiment? Many small drops escaped, didn’t they? Imagine how difficult blocking off an area with booms would be for a real oil spill in the ocean that has waves and wind. You can expand this science project further by seeing how much oil each absorbent material can contain, or how long they can sit in a container of water before soaking it up and getting wet all the way through. For better results, be consistent with the size of strips you use, and time your experiments using a stopwatch. Record the results of your experimenting by keeping a journal on lined paper or a notebook. You can even draw charts or graphs for your lab journal.