Concept: Density, Polarity, and Solubility. Different liquids have different densities, and according to the density, the liquids will settle in a certain order when mixed. Oil is less dense than water and therefore will settle on top of water. Only polar substances will dissolve polar substances. A non-polar substance will not dissolve in a polar substance. This is the rule of "likes dissolve likes".
* 1,000 mL graduated cylinder
* food coloring about 4 drops
* two - 250 mLbeakers
* vegetable oil
1. Fill the graduated cylinder with 800 mL of water
2. Then add the food coloring. Do not let the water become too dark.
3. Slowly pour about 100 mL of the vegetable oil into the 1,000 mL graduated cylinder. It should make a thick layer on top of the water.
4. Measure 25 grams of salt into a 250 mL beaker
5. Slowly sprinkle the salt into the 1,000 mL graduated cylinder on top of the oil. The salt coats the oil and causes it to fall to the bottom of the graduated cylinder in globs. The oil will gradually return to the top of the graduated cylinder.
I am about to create something very interesting that your parents may have had around the house in the 1960's. Carefully watch the experiment and see if you can guess what it is!
Vegetable oil is less dense than water is, and that is why the vegetable oil settles on top of the water. Then the salt coats the oil, which weighs the oil down, because the salt is more dense than water or vegetable oil. For this reason, the added salt causes the vegetable oil to sink to the bottom of the graduated cylinder. However, then the salt begins to dissolve into the water, and separates from the vegetable oil. Without the salt attached to the vegetable oil, it is again less dense than water and so floats back up on top of the water. The reason why the vegetable oil doesn't dissolve into the water happens because of its difference in polarity. Water and salt are both polar, allowing the salt to be dissolved in the water. Oil is non-polar and that is why it cannot be dissolved in salt or water.
Safety: There are NO hazards.
Disposal: All the materials may be poured down the drain.
Reference Source: Unknown