Why does oil float on top of spaghetti sauce?

Here's why:

* Spaghetti sauce is mostly water-based. It's a mixture of tomatoes, water, herbs, and other ingredients.

* Oil is non-polar and doesn't mix with water. Water molecules are polar (they have a positive and negative end), while oil molecules are non-polar. This difference in polarity means they don't attract each other and tend to separate.

* Density is the key. Density is a measure of how much mass is packed into a given volume. Oil is less dense than water, meaning it has less mass in the same volume.

Therefore, the oil floats on top because it's lighter than the water in the spaghetti sauce.

This is the same reason why oil floats on water in general!