Science project
Cleansing Power: How Does Dishwashing Liquid Work?
Have you ever wondered why it takes more than just water to get your clothes and dishes clean? Detergent dissolves in water and attaches to things like dirt and whatever is staining your clothes to help dissolve them into the water to be washed away. But how does dishwashing liquid work, and where does its cleansing power come from?
Most detergents are amphiphilic, which means they are partly hydrophilic and partly hydrophobic. Hydrophilic means a molecule is polar, and thus is attracted to water. Hydrophobic describes to non-polar molecules that don’t like to mix with water.
Objective
Observe how detergent interacts with oil in water.
What will happen when you add detergent to an oil-water mixture?
Materials
- Laundry detergent
- Soap
- Shampoo
- Olive oil
- 4 clear glasses or jars
- Tablespoon
- Water
- Spoon (for stirring)
- Labeling tape
Procedure
- Fill the 4 clear glasses until they are mostly full with water. Make sure each cup has the same amount of water.
- Label the first glass as your control. This glass will contain only clean water so that you can compare it with the other cups.
- In glass 2, add 1 tablespoon of detergent.
- In glass 3, add 1 tablespoon of olive oil.
- In glass 4, add 1 tablespoon of detergent and 1 tablespoon of olive oil.
- Stir each cup vigorously and record your observations.
- Repeat the experiment using different detergents, like shampoo and soap. Record your observations and compare your results.
Results
Cup 2 will be mostly clear with some bubbles produced by the detergent. Cup 3 will have obvious phases, as oil and water do not mix. Cup 4 will be cloudy, as the oil will have bound to the detergent.
Why?
Because detergents are amphiphilic, they help oils become more soluble in water. The hydrophobic (non-polar) parts of the detergent molecules bind to the non-polar oil molecules. Simultaneously, the hydrophilic (polar) parts of the detergent molecules bind with the water so that the entire molecule can dissolve in water. This results in a cloudy solution of water and the molecules formed by detergent and oil.
Education.com provides the Science Fair Project Ideas for informational purposes only. Education.com does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against Education.com that arise thereof. In addition, your access to Education.com's website and Science Fair Project Ideas is covered by Education.com's Privacy Policy and site Terms of Use, which include limitations on Education.com's liability.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.
Related learning resources
