Rhetorical Purpose Questions
12th Question
Types of Mixtures
A mixture is composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes, such as evaporation (you will learn more about this later). A mixture with a composition that varies from point to point is called a heterogeneous mixture. Italian dressing is an example of a heterogeneous mixture. Its composition can vary because we can make it from varying amounts of oil, vinegar, and herbs. It is not the same from point to point throughout the mixture—one drop may be mostly vinegar, whereas a different drop may be mostly oil or herbs because the oil and vinegar separate and the herbs settle. Other examples of heterogeneous mixtures are chocolate chip cookies (we can see the separate bits of chocolate, nuts, and cookie dough) and granite (we can see the quartz, mica, feldspar, and more).
A homogeneous mixture, also called a solution, exhibits a uniform composition and appears visually the same throughout. An example of a solution is a sports drink, consisting of water, sugar, coloring, flavoring, and electrolytes mixed together uniformly. Each drop of a sports drink tastes the same because each drop contains the same amounts of water, sugar, and other components. Note that the composition of a sports drink can vary—it could be made with somewhat more or less sugar, flavoring, or other components, and still be a sports drink. Other examples of homogeneous mixtures include air, maple syrup, gasoline, and a solution of salt in water.
Q. Why does the author say “Note that the composition of a sports drink can vary—it could be made with somewhat more or less sugar, flavoring, or other components, and still be a sports drink”?
a. To show that sports drinks can be both homogeneous and heterogeneous mixtures
b. To make it clear that sports drinks are still homogeneous solutions despite the various compositions
c. To introduce other examples of homogeneous mixtures
d. To describe one exception to the sports drink example
B is the correct answer because the author is clarifying the previous statement, “Each drop of a sports drink tastes the same because each drop contains the same amounts of water, sugar, and other components.” The author includes this note to elaborate on why sports drinks are still homogeneous solutions – because they are mixed uniformly – even though the amounts of each ingredient may vary.