Science trivia

[lamminium]

Biology:

In the biology class, you always get to see the typical animal cell. However, the cells in the real organism vary considerably in their structure. Can you suggest a reason (benefit) for this?

Physiology:

Drug addiction is a major problem. Over the years, physiological studies have attempted to explore the underlying mechanism of addiction in order to control it. There are three prevailing theories regarding addiction. The earlier candidate was "hedonic rewards" which relates increased drug use to pleasure seeking. Another is Solomon's Opponent Process theory which relates exaggerated drug use to development of withdrawal symptoms. However, an emerging theory that also has an equally strong footing suggests something rather different. What is the name of this competing theory?

Physics:

Gravity attracts. Electrostatic forces attract or repel. It appears that the known forces are associated with attraction/repulsion. Name one force that does not have these properties.

Chemistry:

You are familiar with the picture of the atom: a nucleus surrounded by electrons which travel in orbits around it, much like the sun and the planets in our solar system. This model is called the Bohr's model of the atom. However, it is an oversimplification of reality. In other words, the model is wrong. According to our current understanding of the atom, what does it actually look like?

Mathematics:

The Roman numeral system is something you did to death in primary school. Our current number system actually comes from another ancient system which replaced the Roman numerals in Europe and ultimately worldwide. What is the name of the numeral system that we currently use? Note: decimal system is not the answer. "Decimal" just refers to the use of ten numbers (0 to 9) as the base of the system.

Edited October 15, 2009 by lamchopz

[vincent]

Physics:

Nuclear force

Chemistry:

electron cloud surrounding the nucleus

[wmoley2k]

I was under the impression the nuclear force does attract and repel. It keeps nuclei together doing so. The weak interaction, also known as the weak force, could be the answer. Maybe?

Edit:

Also, we use Arabic numerals.

[zhangm Supervisor]

In the biology class, you always get to see the typical animal cell. However, the cells in the real organism vary considerably in their structure. Can you suggest a reason (benefit) for this?

Specialization. Form facilitates function, which is why, for example, some neurons are long, and plasma cells are full of ER.

I also don't consider atoms to really look like anything. They're a nucleus surrounded by a probability distribution describing where the electrons are likely to be found.

Here's one that I like.

If you pour oil into water, you'll observe that the two liquids separate into different phases. Does this make sense energetically, and if so, why (yes, you can look it up, but it is interesting to reason it out).

Edited October 15, 2009 by Relativity_17

[lamminium]

I wrote these questions for a guild trivia tournament in an MMO I played. :p

I thought I should share them here as well. As expected, you guys respond very quickly!

Physics:

Nuclear force

Chemistry:

electron cloud surrounding the nucleus

I was under the impression the nuclear force does attract and repel. It keeps nuclei together doing so. The weak interaction, also known as the weak force, could be the answer. Maybe?

Edit:

Also, we use Arabic numerals.

Yes, the weak interaction is the correct answer. Its major role is change one quark to another (which is less massive and/or in lower generation).

Our system is indeed called Hindu-Arabic numeral system.

Specialization. Form facilitates function, which is why, for example, some neurons are long, and plasma cells are full of ER.

I also don't consider atoms to really look like anything. They're a nucleus surrounded by a probability distribution describing where the electrons are likely to be found.

Here's one that I like.

If you pour oil into water, you'll observe that the two liquids separate into different phases. Does this make sense energetically, and if so, why (yes, you can look it up, but it is interesting to reason it out).

Specialisation is a good reason. It allows the cell to direct energy only to the components needed for its function.

Your answer to the anatomy of the atom is what I would like to see because at quantum level, it is all about probabilistic events. Electron cloud surrounding a nucleus is the answer that I originally had in mind (I didn't expect a lot from my guild members in the game since some of them are really young lol)

For the liquid/water phase separation question, it makes sense to me because oil molecules are hydrophobic so it would be more energetically economical to separate them from water.

Now here's what I've been wondering for a while: are you studying/working in science? :p

[vincent]

I was under the impression the nuclear force does attract and repel. It keeps nuclei together doing so. The weak interaction, also known as the weak force, could be the answer. Maybe?

Edit:

Also, we use Arabic numerals.

I was going to edit my post to specify the weak nuclear force lol i knew it was one or the other.

[zhangm Supervisor]

For the liquid/water phase separation question, it makes sense to me because oil molecules are hydrophobic so it would be more energetically economical to separate them from water.

Now here's what I've been wondering for a while: are you studying/working in science? :p

Is the favorability primarily a function of enthalpic or entropic cost (hint: the answer might be counterintuitive if you think of the system on a macroscopic level)?

Yeah, I suppose you could say that I work in science...

[lamminium]

It's not counterintuitive actually. I think of entropy in this form S(universe) = S(system) + S(surrounding) owing to my second year Thermal Physics class. The entropy of our system which consists of water/oil decreases which is perfectly ok because the entropy of the surrounding increases much more rapidly, effectively ensuring the entropy of the universe always increases.

[zhangm Supervisor]

It's not counterintuitive actually. I think of entropy in this form S(universe) = S(system) + S(surrounding) owing to my second year Thermal Physics class. The entropy of our system which consists of water/oil decreases which is perfectly ok because the entropy of the surrounding increases much more rapidly, effectively ensuring the entropy of the universe always increases.

Ok, if we allow that delta S is negative, then return to our equation:

∆G = ∆H - T∆S

We know that ∆G is less than 0 because the observed reaction is spontaneous at room temperature (so T = 298 K). If ∆S is negative, then the term -T∆S must be positive, thus for the process to be spontaneous, ∆H must be negative.

What if you knew that ∆H is positive for this change, and the solubility of oil in water increases with temperature? What conclusions could you draw?

[lamminium]

How do you render the delta symbol? lol

First is dH positive because the internal energy increases in isobaric and isochoric conditions? If so, dT > 0.

G = H - TS -> dG = dH - d(TS) = dH - TdS - SdT

For the process to be spontaneous, dG < 0 implying that |SdT| > |dH|+ |TdS| at a particular T. It seems to explain the solubility of oil molecules with increasing termperature.

I guess the separation of oil/water entails a decrease in temperature?

EDIT: I changed the Physiology question because there is also another theory which was unfortunately not covered in my Neurophysiology course so it slipped my mind when I wrote the question. :p

Edited October 15, 2009 by lamchopz

[lamminium]

^ Screwed up my algebra a bit: meant to be |SdT| + |TdS| > |dH| when T increases and S(system) increases, explaining the hydrophilicity index.

[zhangm Supervisor]

I guess the separation of oil/water entails a decrease in temperature?

There isn't any significant change in the temperature of the solution between mixed and separated states. The point is that the spontaneous separation of oil and water into two phases is primarily driven by entropic favorability - in layman's terms, the final state of a two-phase solution is less ordered than the initial mixture. ∆S is positive, and the -T∆S term is of sufficient magnitude to overwhelm the enthalpy term.

[lamminium]

^ Can you elaborate on why that is?

[zhangm Supervisor]

Water molecules are polar, and aliphatic molecules such as those of many oils, are not. Water molecules can participate in hydrogen-bonding interactions that essentially absorb their partial charges, and this is more favorable than a solution full of like charges crashing into each other. Looking at any single water molecule in solution, it is surrounded on all sides by other water molecules, and thus has a large sphere that potential H-bond partners can occupy. If you then put an aliphatic molecule right up next to that water molecule, you suddenly create this surface that excludes a significant amount of those stabilizing interactions, and now the water molecule has a bit less than one hemisphere that potential H-bond partners can occupy. In essence, the presence of an aliphatic molecule adjacent to water molecules constrains their position in space because there is a smaller set of favorable interactions available to them. What you observe is that the water molecules in "direct contact" with a hydrophobic molecule will adopt a semi-rigid cage called a clathrate. Since typically, a molecule of oil is large and long, it saps conformational freedom from the many water molecules around it, and hence, the entropy of the solution drops as you solvate more and more oil. The energetically favorable solution then is to shove all the oil molecules into one space, and all the water molecules into another to minimize their interaction.

[lamminium]

In other words, separation increases the number of the degrees of freedom?

[lamminium]

While waiting to discuss more about entropy with Relativity_17, I think I should answer this question:

Physiology:

Drug addiction is a major problem. Over the years, physiological studies have attempted to explore the underlying mechanism of addiction in order to control it. There are three prevailing theories regarding addiction. The earlier candidate was "hedonic rewards" which relates increased drug use to pleasure seeking. Another is Solomon's Opponent Process theory which relates exaggerated drug use to development of withdrawal symptoms. However, an emerging theory that also has an equally strong footing suggests something rather different. What is the name of this competing theory?

"Incentive salience" which relates increasing "want" to increased drug use (this came from the observation that euphoria was absent as usage progressed).