The connectivity of Concept

Today, I was mulling over some ideas to write about. I was drawn to the article that I saw in BBC Science about a mountain range in Antarctica that is below the ice cap. It is certainly not the “Mountain of the Blue Moon” from the book Lost Horizon, however, a unexplored mountain is still very intriguing – even if it is under an ice sheet. Here is the address for this article: http://news.bbc.co.uk/2/hi/science/nature/8420837.stm .

I have also been thinking about a short video clip that I saw in my Science methods teaching class. This video showed a kid experimenting with Mentos and diet coke. Here is the link for the Wikipedia page on that experiment: http://en.wikipedia.org/wiki/Diet_Coke_and_Mentos_eruption .

After looking at both, it turns out that I do not have to choose as both ideas have a common theme! What could a kid exploding experiment and a buried mountain chain have in common you wonder? Well, the answer is a concept called nucleation.

Here is the deal on the diet coke / Mentos experiment:

“MythBusters concluded that the caffeine, potassium benzoate, aspartame, and CO2 gas contained in the Diet Coke and the gelatin and gum arabic ingredients of the Mentos all contribute to the jet effect. In addition, the MythBusters theorized that the physical structure of the Mentos is the most significant cause of the eruption due to nucleation”.

And here is the deal on the Antarctic Mountain range:

It led many to speculate that the Gamburtsevs might be old "hot spot" volcanoes that had punched their way through the Earth's crust, much like the Hawaiian Islands have done in the middle of the Pacific.

The range has since become the subject of intense scientific fascination because it was almost certainly a nucleation point some 30 million years ago for the huge ice sheets now covering Antarctica.

So, what exactly is nucleation anyway? Well, here is a brief description:

“Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form via nucleation in liquids are gaseous bubbles, crystals, or glassy regions” Available: http://en.wikipedia.org/wiki/Nucleation .

To me, the most interesting thing is that these two seemingly totally unrelated phenomenons have a common physical theme. In many ways, it showcased a reason for us the study aspects of science that may seem impractical. Most of us will never have to worry too much about the genesis of an Antarctic mountain range and I think that it is safe to say that we will never need to challenge ourselves with erupting soda pop.

It is interesting to note, however, that there are many other instances of nucleation. The following is a list of examples of nucleation:

• Pure water freezes at −42°C rather than at its freezing temperature of 0°C if no crystal nuclei, such as dust particles, are present to form an ice nucleus.

• Presence of cloud condensation nuclei is important in meteorology because they are often in short supply in the upper atmosphere (see cloud seeding). From my recent Meteorolgy class, I would add that the most recent theories suggest that rain cannot fall without a condensation nuclei as condensed liquid water is bouyant in the atmosphere/

• All natural and artificial crystallization process (of formation of solid crystals from a homogeneous solution) starts with a nucleation event.

• Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid. Nucleation often occurs more easily at a pre-existing interface (heterogeneous nucleation), as happens on boiling chips and string used to make rock candy. So-called Diet Coke and Mentos eruptions are a dramatic example (as mentioned above).

• Nucleation in boiling can occur in the bulk liquid if the pressure is reduced so that the liquid becomes superheated with respect to the pressure-dependent boiling point. More often nucleation occurs on the heating surface, at nucleation sites. Typically, nucleation sites are tiny crevices where free gas-liquid surface is maintained or spots on the heating surface with lower wetting properties. Substantial superheating of a liquid can be achieved after the liquid is de-gassed and if the heating surfaces are clean, smooth and made of materials well wetted by the liquid.

• Nucleation is relevant in the process of crystallization of nanometer sized materials,and plays an important role in atmospheric processes.
• Nucleation is a key concept in polymer, alloy, and ceramic systems.

• In chemistry and biophysics, nucleation can also refer to the phaseless formation of multimers which are intermediates in polymerization processes. This sort of process is believed to be the best model for processes such as crystallization and amyloidogenesis.

• In molecular biology, nucleation is used to term the critical stage in the assembly of a polymeric structure, such as a microfilament, at which a small cluster of monomers aggregates in the correct arrangement to initiate rapid polymerization. For instance, two actin molecules bind weakly, but addition of a third stabilizes the complex. This trimer then adds additional molecules and forms a nucleation site. The nucleation site serves the slow, or lag phase of the polymerization process.


That is quite a lot of examples that tie in the Mentos / Coke kid and the submerged mountain range!

As we educate our children in science, it is difficult, sometimes, to see the value in watching of doing experiments like the coke explosion. However, we can see from the list, that if the right connections are made, not only can science be fun; it can also lead to concepts that will enhance our society and also further the development of science and technology in our world.

Sultry World Found Circling the Star GJ 1214 - NYTimes.com

The world of astronomy just keeps getting “curiouser and curiouser”. This is one of what I believe will be a spate of articles published about exo-planets:

Sultry World Found Circling the Star GJ 1214 - NYTimes.com

What is most interesting is the idea that liquid water can exist at 400 degrees F. How can we have a liquid ocean at such a high temperature? Does water not boil at 212 degrees F? What is the reason for this claim in this article?

The answer (or at least what I thought of today) is that water boils as 212 degrees F under normal conditions, but conditions on this world are certainly not normal! Although we cannot go there and make direct observations, we can infer some of the possible conditions on this planet. We can also use some of our engineering and physics knowledge here on Earth to help us get a grip on this concept.

For instance, do we know of conditions where water would not boil at 400 degrees F? The answer is yes. The below link shows us an engineering graph of the boiling point of water based on different pressure conditions:

http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

We can see from this diagram that we can have many conditions where water would be able to be liquid and still be that hot as long as the needed pressure condtions were met. Reading the graph, we see that it is possible for water to be liquid if the pressure is greater than approx 280 psi.

Needless to say, it does not sound like a hospitable world for us, be as we have seen on Earth - life finds a way!

What is in a question?

I have finally returned to adding some new material. As part of my teaching experience, I am currently taking a class in Science teaching methods. My professor has a very interesting method for using multiple choice questions to promote higher order thinking. You can view some of the discussion at the blog:

http://problemfinding.labanca.net/

On one of his other blogs, he gives an example of a multiple choice question that requires quite a bit of thought. Here is the question from my professor:

Q. Insects with wing mutations that prevent flight (e.g., in fruit flies, some flies have crumpled wings throughout their lives) usually can’t survive long in nature. Flightlessness is selected against. But in three of the following environments the trait could actually be selected for. In which environment would useless wings NOT be selected for?

MY professor uses multiple choice questions to stimulate higher order thinking instead of simply testing for recall of knowledge or facts. Here are my thoughts on his different multiple choice options:

a. an island where stiff winds blow some flying insects out to sea, never to return.

I did not think that this was the best because of the fact that only some flying insects were blown out to sea. Fruit flies that had crumpled wings would be less likely to be selected against, yet not all of the un-mutated flies would necessarily be sent out to sea – so who is more likely to survive – a lessened population of un-mutated flies or a mutated crumpled wing fly?

b. a swamp full of frogs that can see and catch flying insects better than crawling insects.

I also did not think that this was the best answer. One reason is that e the entire island is not likely to be covered by one swamp. Therefore, even though the swamp frogs may have a negative effect on the population of fruit flies, this does not mean that fruit flies with wings will be selected over crumpled-winged flies. Rather, winged flies will be under more pressure as they are more likely to be targeted in the swampy area.

Also, this statement does not say that frogs cannot catch crumpled winged flies, only that they can see and catch flying insects better. So, the inference is that they may also be able to catch crumpled-winged flies, but that catching the flying ones is only easier.

c. a forest full of bats that catch and eat insects while in flight.
In my mind, this would be the best answer of where useable wings would be selected against and useless wings would be selected for and not against.

My reasoning for this is that useless wings would NOT be selected because flying bats in a forest would be eating only the fruit flies with usable wings as they, “Catch and east insects while in flight” and only un-mutated fruit flies can fly so only un-mutated fruit flies can be eaten and selected against.

The inference in this answer is that the bats do not eat insects on the ground. Given my knowledge of bats and the way the choice is worded, that should be a fair assumption.

d. a cage with predators, who crawl along the base

This seemed like the “chestnut” – my term for the easy answer. Certainly the crumpled wings would be selected against since flying insects could fly away and crumpled insects would be on the bottom of the cage and more easily caught.

Here is one possible issue with this answer – is a cage an environment? In the most narrow sense certainly, but would this environment really be an element of evolution or just a lab experiment?

With all that said, this would appear to be the clearest negative case of an environment where useless wings would be selected against, not for. So, going back to the wording of this question, “In which environment would useless wings NOT be selected for?” – this choice would best satisfy the task in my mind.

What is the point of all of this? For me, it was the thought provoking aspect of this question. Instead of just recalling a fact or concept, I was forced to apply my knowledge to think about the different responses. This HOTS (Higher Order Thinking Question) helped me to think and write more about the selection mechanism of evolution.

A note on question wording…

I would point out though, one issue that I myself would caution on using a question such as this, and that is that like many people, I have trouble with “NOT” questions. As part of our educational training, we have received instruction on avoiding the negative questions. After carefully re-reading the responses, I still almost went for choice c as this was the clearest case to me of winged flies being selected against.

However, this question asks in which environment “Would useless wings NOT be selected for. Clearly the best answer, in my mind is d. The problem that I had was keeping the “NOT” straight in my mind.

In the end, I had to go back a few times and re-read the question to be sure that I was clear on what was being asked. I think that as a teacher, it is important to help student not only with scientific material, it is also important for teachers to help students with skills.

In questions such as these, you may need to have a quick “mini-lesson” in test taking skills and help students to recognize these questions. One aid might be to train students to underline the word “NOT” in the question. Also you may want to help student organize their thinking and responses. For instance, a very quick “T” chart could be created showing environmental influences that would help winged flies on one side and crumple wings on another side.

Another idea is that students could be taught a very simple skill of writing out something like “Good for crumpled wings”, “Bad for crumpled wings”. This would help them think about the meaning of each choice and then be able to go back and re-read the question and provide the best answer.

A third strategy might be to have students re-write the question or at least re-think it in their own mind. In the specific example, I took the phrase, “In which environment would useless wing NOT be selected for”, and physically re-wrote it as, “In which environment would useless wing be selected against”. By re-writing, or re-thinking the question, I was able to more clearly understand the task at hand and this helped me to better answer the question.

These types of skill can help students to think more about their questions as well as gain more knowledge about their work with the side benefit of helping them achieve more on standardized tests that will inevitably come their way