Is a oil-and-vinegar salad dressing homogeneous or heterogeneous substance?

Here's why:

* Heterogeneous mixtures have components that are visibly distinct and can be easily separated.

* Homogeneous mixtures have components that are evenly distributed and appear as one substance.

In an oil-and-vinegar dressing, the oil and vinegar separate into distinct layers. The oil, being less dense, floats on top of the vinegar. This clear separation indicates that the mixture is not uniform throughout and is therefore heterogeneous.