Name _____________________________________ Period ____
Why don’t oil and water mix?
http://ed.ted.com/lessons/why-don-t-oil-and-water-mix-john-pollard
1. Energetics deals with ________.
a. The strength of attractive and repulsive forces between the substances
b. The number of ways that a substance can arrange itself and distribute energy
c. Whether or not something dissolves in water
d. Is the only factor that can explain why salt dissolves in water
2. Which statement best describes the “hydrogen bonding network”?
a. Water molecules interacting with each other in constant motion analogous to a square dance
that looks very organized
b. Water molecules interacting locked into position analogous to a large group of people holding
hands and dancing together
c. Water molecules moving around randomly but not interacting with any other water molecules
analogous to people avoiding each other at a dance
d. Water molecules interacting with each other in constant motion analogous to a square dance
that looks very random
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3. When salt dissolves, ________.
a. The chlorine and sodium ions are separated and enter into the hydrogen bonding network
analogous to them leaving their group and joining the waters dance
b. The chlorine and sodium ions stay in a big group analogous to the ions entering the dance
floor all together without separating
c. The chlorine and sodium ions form molecules and stay together analogous to them staying as
partners when they enter the dance
d. The chlorine and sodium molecules are separated and enter into the hydrogen bonding
network analogous to them leaving their group and joining the waters dance
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4. When oil molecules are put into water, they _______.
a. Are more attracted to themselves than the water so they show no interest in “dancing” with the
water molecules
b. Are attracted to the water molecules but disrupt the hydrogen bonding network so are pushed
out. This is analogous to the oil molecules being poor dancers and being kicked off the dance
floor by the water molecules
c. Are attracted to the water molecules but are too small to enter the dance so stay on the side
d. Are really good at doing the “hydrogen bonding network dance”. So good in fact that they
waters become jealous and kick them off the dance floor
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5. Entropy is best described as ________.
a. A measure of the strength of attractive forces between things
b. A measure of how well something dissolves in water
c. A measure of the number of ways that the particles that make up a substance can be arranged
and distribute energy
d. A measure of the weakness of attractive forces between things
6. In the video, “dancing” is used as an analogy to convey the ideas of energetics and entropy.
Can you build an explanation for why salt dissolves and oil doesn’t without using an analogy or
personifying the ions and molecules (referred to as anthropomorphism)? Use only the definitions
of energetics and entropy when building your explanation.
7. There are compounds similar to salt that do not dissolve in water. An example is calcium
carbonate which is comprised of calcium and carbonate ions. Can you build an explanation using
the dance analogy from the video for why this substance does not dissolve in water? (Hint: The
ions are very attracted to water as is the water very attracted to the ions…but the stuff still
doesn’t dissolve.) After you have built your dance analogy explanation, try to build an
explanation that doesn’t not use any analogies or personify the ions and molecules.
8. A surfactant is a molecule that can dissolve in both oil and water and can be added to an oil
spill to help facilitate the mixing of the oil and water (which can make it easier to disperse an oil
spill). Can you build an explanation using the dance analogy for how a surfactant might work on
mixing oil and water? Then try to build an explanation without using analogies or personifying
the molecules. (Remember, by avoiding personification of molecules you cannot say that they
“like” or “want” things. Just focus on energetics and entropy!)
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