EXPERIMENT 4.1
POLARITY OF WATER
PURPOSE:
To observe the attraction of polar and nonpolar molecules to a static electrical charge.
MATERIALS:
- A Styrofoam or paper cup
- Glass of water
- Vegetable oil
- Balloon
- Pen
- Eye protection such as goggles or safety glasses
QUESTION:
How will a stream of water (a polar substance) and a stream of vegetable oil (a nonpolar substance) react when a balloon with a static negative charge is brought near?
HYPOTHESIS:
Write your prediction of what a stream of water will do when a charged balloon is brought near.
Write your prediction of what a stream of oil will do when a charged balloon is brought near.
My Hypothesis:
PROCEDURE:
- Use the pen to punch a small hole in the bottom of the cup. The smaller the hole, the better.
- Blow up and tie off the balloon. Set near the sink in easy reach.
- While holding the cup over the sink, fill the cup with water from the glass. Water should start running out of the hole in the bottom of the cup. Make sure that the water is pouring out of the hole in a steady stream, not dripping. If it is dripping, make your hole just a little larger.
- Once the water is pouring out of the cup in a steady stream, pick up the balloon with your other hand and rub it vigorously in your clean, dry hair. This is meant to make the balloon develop an electrical charge. If your hair is wet or oily, this may not work too well. You can also charge the balloon with different fabrics so try using your clothes if your hair isn't working.
- After you have rubbed the balloon in your hair (or clothes) for a few seconds, bring the balloon (the side you were rubbing) near the stream of water. Bring the balloon close but do not actually touch the water stream. Write your observations in your data table.
- Repeat this same experiment using vegetable oil instead of water. You may have to make the hole a little bigger this time, because vegetable oil doesn't flow as easily as water does. You should also catch the oil in a jar to save for the next experiment. Record your observations in your data table.
- Clean up and put everything away.
DATA TABLE:
| Substance | Observation when charged balloon is brought near |
|---|---|
| Water (polar) | |
| Vegetable Oil (nonpolar) |
CONCLUSIONS:
Explain your observations and the difference between the way oil behaves and the way water behaves when both are exposed to an electrically charged balloon. Use the term polarity in your explanation and make connections to the text.
My Conclusion:
VIDEO DEMONSTRATION:
Watch this video demonstration to observe how polar water molecules react to a charged balloon compared to nonpolar oil molecules.
Note: If the video doesn't load, you can watch it directly on YouTube.
What to Observe:
- Water stream: Notice how the water stream bends toward the charged balloon, demonstrating that water is polar.
- Oil stream: Observe that the oil stream falls straight down, unaffected by the charged balloon, showing that oil is nonpolar.
- Scientific explanation: Water molecules have positive and negative ends (polar), so they're attracted to charged objects. Oil molecules don't have distinct charges (nonpolar), so they're unaffected.