You may have heard the saying “oil and water don’t mix.” It’s true! If you’ve never seen oil and water together in the same container, you will soon! The reason oil and water don’t mix is because they have different densities. Oil is less dense than water, which means that it weighs less. Because water is more dense, it sinks to the bottom of the container. Because oil is less dense, it will always float to the surface of the water.
Test it out!
Fill an empty water bottle about three-fourths full with water. Add about a half-cup of oil to the bottle. What happens? The oil just sits right on the surface. Tip the bottle upside-down. The oil rises to the top and the water sinks to the bottom. What do you think will happen when you shake up the bottle? Try it out! It may look like the oil and water have mixed, but it’s only temporary. You probably see that the bottle looks to be filled with a bunch of bubbles. This is the oil broken up by the vigorous shaking. Eventually, all the oil will rise back to the top.
We took this demonstration a step further a few weeks ago when we made our own lava lamps out of colored water and vegetable oil: http://discoveryexpress.weebly.com/blog/make-your-own-lava-lamp.
You just saw a small example of how oil is insoluble in water. Insoluble means that the oil does not dissolve or mix in with water. Why would this matter in real life? Oil is a commodity that is always being shipped across the ocean to different areas. Sometimes, there are mistakes and oil is spilled into the ocean, possibly because of a leak in an oil tanker. Why would this matter? While oil sits on top of the water because it’s insoluble, it is extremely difficult to remove from the water. That’s what we are going to focus on today!
Check out this link to learn more about oil spills and why they are a BIG DEAL: http://www.kidzworld.com/article/24170-oil-spills-sad-but-true
How do we deal with oil spills? Read this article about how oil is removed from water: http://www.livescience.com/32524-how-are-oil-spills-cleaned.html
The question of the day: What is the most effective way to remove oil from water? In this experiment, you will use different materials to act as surface skimmers, the first of the four oil spill cleanup methods you just read about on livescience.com.
YOU WILL NEED:
- Vegetable oil
- Clear container
- Dry-erase marker
- Tools: Cotton balls, gauze, polypropylene cloth
Here’s what to do!
1. Fill your clear container half full with water.
2. Add vegetable oil to the container of water until you have at least a half-inch layer of oil sitting on the top. This is your oil slick.
3. Use a dry-erase marker to mark the where the surface of the oil is. This is your reference point to see how much oil you can remove with your materials.
4. Make a prediction about which tool will work best for removing the oil from the water. Why do you think this will work the best?
5. Make a chart to record your observations. It may look something like this:
7. Add more oil to the container until the level is the same as it was before you used the cotton balls. Now, test out the polypropylene cloth. How effective is this material? Does it take more or less time to remove the oil? Were you able to remove more oil?
8. Last, try out the gauze. Record your observations as you did with the first two materials.
9. Draw conclusions and record your final thoughts. Which tool worked the best to remove the oil?
Extension: You’ve tried removing oil from water, but sometimes when oil spills occur, the oil that spilled in the ocean makes it to shore and coats the sand. How difficult is it to remove oil from sand? Will the same techniques work? Fill a cup with sand and then dump half a cup of vegetable oil into it. Use a spoon to stir the oil into the sand until its well blended. Now, test all the methods out to see how much oil you can remove. You could even try to use soap! Which method was most effective in removing the oil from the sand?