A student makes salad dressing by combining vegetable oil, vinegar, salt, pepper, mustard, and thyme. None of the ingredients are measured.

The next time the student makes salad dressing, basil is used in place of the thyme. Which classification best describes the salad dressing?

A. Element
B. Compound
C. Homogeneous mixture
D. Heterogeneous mixture

The salad dressing with unmeasured amounts of oil, vinegar, and herbs is a heterogeneous mixture due to its variable composition and the fact that it is not uniform throughout.

Explanation:

The salad dressing described by the student, which contains vegetable oil, vinegar, salt, pepper, mustard, basil, or thyme, would be classified as a heterogeneous mixture. In a heterogeneous mixture, the composition is not uniform throughout, which means the ingredients do not blend together completely, leading to parts of the mixture having different concentrations of ingredients.

An example to illustrate this is that one portion of the salad dressing may contain more oil while another may have more vinegar or herbs. This variability in composition is typical for salad dressings where the oil and vinegar separate and the solid ingredients like herbs settle, just as with Italian dressing which is a classic example of a heterogeneous mixture.