Final answer:
Salad dressings are heterogeneous mixtures that consist of two or more substances that are not evenly distributed throughout.
Step-by-step explanation:
Salad dressings can be classified as heterogeneous mixtures. They consist of two or more substances that are not evenly distributed throughout. In the case of oil and vinegar salad dressing, the oil and vinegar are immiscible liquids that separate into distinct layers when left undisturbed. This lack of uniformity in composition makes it a heterogeneous mixture.