Video Transcript
Which the following substances or
phenomenon is an example of an emulsion, which is a liquid dispersed through a
liquid? (A) Milk, (B) air, (C) fog, (D)
whipped cream, or (E) smoke.
Let’s start by narrowing down our
answer choices based on the composition of each type of mixture. Milk is primarily made up of water
and water-soluble components like salt and sugar. Milk also contains other components
that are not water soluble, such as liquid oils and fats. These oils and fats are tiny
droplets that are dispersed throughout the water layer. And since milk is mostly made up of
liquid oils and fats dispersed through water, we can classify this as an
emulsion.
Answer choice (B), air, is a
complex mixture of gases that make up our atmosphere. It’s made up of 78 percent
nitrogen, 20.9 percent oxygen, 0.9 percent argon, 0.03 percent carbon dioxide, and
0.17 percent of other gases. Looking at the chart, you’ll notice
that each of these components is in the gas phase. And since air is a mixture of gases
and not a liquid dispersed through a liquid, we can eliminate answer choice (B).
Answer choice (C), fog, is a very
common mixture throughout nature. It’s composed of lots of tiny water
droplets that are dispersed throughout air, which is a gas. Now even though the water droplets
are incredibly small, they’re still in the liquid phase. And so since liquid water droplets
are dispersed through the gaseous air, we can eliminate answer choice (C).
Whipped cream, like you would find
at the grocery store, is made when heavy whipping cream is stirred vigorously. Like milk, heavy cream is made up
of mostly water and water-soluble components, but it also contains a significant
amount of lipids and fats. When stirred vigorously enough, it
entraps air into the water–lipid mixture, forming a colloid. And so since whipped cream is
colloid composed of a gas dispersed in a liquid, we can eliminate answer choice
(D).
And finally, let’s take a look at
answer choice (E), smoke. Smoke is formed when organic
material like wood is incompletely burned. And this incomplete burning leads
to small solid particulate dispersed in the air. And so because smoke is a solid
dispersed in a gas and neither are liquids, we can eliminate answer choice (E).
And now with this information, we
should be able to answer the question. Which of the following substances
or phenomenon is an example of an emulsion, which is a liquid dispersed through a
liquid? And the correct answer is answer
choice (A) milk.
