In spite of the title, this experiment does not deal with cold weather or clothing. Instead, we will look at some of the chemistry of salad dressing. If you look at a bottle of Italian dressing, you will notice that it separates into two layers, the oil on top and the vinegar on the bottom. Why cover those wonderful greens and veggies with two liquids that don't mix?

To find out, you will need:

- small bowls or containers
- water
- cooking oil
- dried oregano and other spices
- salt

Put a little water into one bowl, and a little cooking oil in another. Sprinkle a little salt into each and stir. What happens? In the water, the salt quickly vanishes. It has dissolved in the water. In the cooking oil, it just sits there. Why the difference?

Lets start by picturing a water molecule. Water has the chemical formula H2O, which means that each molecule is made up of two hydrogen atoms and one oxygen atom. The two hydrogen atoms attach to one side of the oxygen. Think about Mickey Mouse, with his head and two big ears, with the oxygen atom being his head and the hydrogen atoms forming the ears. Just as the shape looks off balance, the electrical charges are off balance too. The oxygen atom winds up with a negative charge, and the hydrogen atoms get a positive charge. These charges are at opposite ends of the molecule, just like the poles of a magnet, making this a polar substance.

On the other hand, the cooking oil, like other oils, is not polar. Its protons and electrons are balanced; making it neutrally charged on all sides. With no charge, the oil is not attracted to the water. The water molecules all stick together, keeping the two from mixing.

Table salt has the chemical formula NaCl, telling us it is made up of sodium and chlorine. The sodium and chlorine are held together by charges, with the sodium being positive and the chlorine being negative. As with magnets, opposite charges attract. When you put salt into water, the positive hydrogen atoms in the water pull on the negatively charged chlorine. The negative oxygen atoms in the water pull on the positively charged sodium. The salt comes apart into charged particles known as ions, and dissolves in the water. In oil, nothing is pulling on the sodium and chlorine atoms, so they stay together and do not dissolve.

Things can also work the opposite way. Some substances will dissolve in the nonpolar oil, but not in water. Some of the flavor components in spices are oils, which will not dissolve in water. You can see this by repeating the experiment using oregano instead of salt. After you mix the spice into the oil and the water, let it sit in a warm place for a few hours. Then carefully taste each. Be sure that you don't get any of the actual spice in your taste sample. You just want to taste the oil and the water. I had good luck with a medicine dropper. It helps if you eat a bite of bread or cracker before each tasting, to clear your taste buds.

You should find that both oil and water are flavored, but the flavors will be different. The water will have a much stronger aroma, because water evaporates easily, carrying the smell into the air. It will carry some of the "lighter" flavors and the bitterness. When you taste the oil, you get the richer flavors from the spice. Finally, taste both together, or one right after the other, and you will get the full flavor of oregano. I tried this with chili powder too, with the same results. By the way, the oil also dissolves the oils that give chilis their hot flavor. That is why water does not help when you eat a hot pepper. Milk, with its milk fat, does a much better job of dissolving the hot components of the peppers.

Now, lets get back to the oil and vinegar in salad dressing. The polar vinegar does not blend with the nonpolar oil. Each brings its own flavor, plus the flavors of the spice elements that it can dissolve. When you put them all together, you get a wonderful blend of flavors for your salad.