Mentos and Diet Coke: The Truth Revealed!

The title of this article has probably already made you come to the conclusion that it is going to be like any of those highly sought for forum articles or frequently viewed YouTube videos. Yes, videos and articles which feature “Do It Yourself” formulas of making an exploding mix of Mentos and Diet Coke. But I guarantee that this article discusses something little different though related.

By now, many of you have already come to know about the Mentos-Diet Coke explosion phenomenon. It has been the topic of discussion for quite a long time and the visual splendor of Coke shooting from two liter bottles to extraordinary heights has attracted so much attention in the past few months that the topic even made its way to famous programs like the Mythbusters or Timewarp aired on the Discovery channel.

Each and every video I watched and writing I read about this famous topic emphasized on how an eruption could be made to produce a “Coke Geyser”. Many of you might still have the formula in your mind:

4 Mentos + 2 Liter Diet Coke = Kabooooom!

Typical Coke Geysers

But I was really curious to find out why actually the phenomenon occurred. With a little help from my friends, teachers and the internet, I tried my best to piece together the moments just before an eruption occurs when Mentos is dropped into Diet Coke and this is what this article is all about.
The reaction between Mentos and Diet Coke is more of a physical reaction than chemical. Coke is mainly water with dissolved carbon dioxide, flavorings, and sweeteners. In most liquids, there is some dissolved gas. In high surface tension liquids like water, it is tough for bubbles to form because water molecules tend to be next to each other due to capillary forces. In order to form a new bubble or even to expand a bubble that has already formed, water molecules must be pushed away from each other. It takes extra energy to break this tight mesh of linked water molecules.

Surface Tension Leads To the Formation of Stable Liquid Drops

When Mentos candy is dropped into Diet Coke, the gelatin and Gum Arabic in the coating of the candy act as efficient surfactants. They lower the surface tension of the Coke and reduce the work done to produce bubbles. In Diet Coke, artificial sweeteners instead of sugars are used which are better surfactants. Also, the rate of reaction between Mentos and Coke with artificial sweeteners (i.e. Diet Coke) is very fast than that with conventional Coke.
The surface of Mentos is very rough. When magnified, the surface of Mentos can be seen to have numerous pits. These pits act as nucleation sites encouraging formation of bubbles on them. Though nucleation site theory is not yet clearly understood, but some scientists argue that at the nucleation sites, the curvature of bubbles get reduced and hence the surface energy is also small there. Thus at those sites, bubbles are preferentially formed. Some others argue that at the nucleation sites, the pattern of electrical forces between solvent molecules change which allow solute molecules to break free and escape (in the form of bubbles if the solute is a gas). It is based on this nucleation phenomenon, radiation detectors like Bubble chambers and Cloud chambers work.

Nucleation of carbon dioxide Around a Finger

Mentos candies are relatively heavy and thus they sink to the bottom as soon as they are added to Coke. The sinking Mentos undergoes a rapid physical reaction with the Coke. This coupled with the low surface tension of the Coke and the introduction of numerous nucleation sites leads to the formation of a large number of bubbles in a very short time. These evolving bubbles ascend and push all the liquid Coke above them with great force to cause an impressive eruption. This produces the characteristic “Coke Geyser”.
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By Mahmud Hasan
The Aftermath Publications
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The Aftermath Publications, Issue 2

Stars: Birth to Death

It does not take an expert eye to discover the magnificence of the night sky. It has so much to offer, in the form of its pitch black darkness adorned by equally bright dazzling dots what we more commonly know as stars. Stars are probably the most amazing celestial creations. They embellish the vast emptiness of the sky with their charming hues and brightness so efficiently that they still remain the centers of attraction to astrologers, scientists and philosophers.

Early philosophers believed that stars are gods, who constantly show up in the night skies to impose their presence by brilliance and to inspire people do good deeds for the next day. This is of course not a valid proposition anymore on scientific grounds. So what actually a star is?

Stars Dominate the Night Sky

Astrophysicists use observations to suggest theories of how stars come into being. Interstellar space is not a perfect vacuum as you might expect. Rather it is a low density mixture of atoms, molecules and microscopic specks of dust. In places these form greater concentrations, which appear as large gas clouds.

Interstellar Gas Clouds

A close look at the night sky with a telescope reveals the existence of the gas clouds along with stars and planets. The most available element in these clouds is hydrogen. The most plausible theory is that stars begin as clouds of hydrogen.

Despite the extreme tenuousness of these clouds, gravitational force is predominant force that acts on the particles of the cloud. This pulls the particles together and they accelerate inwards. They collide increasingly frequently sharing their energy. The temperature of the gas thus rises. Therefore gravitational energy is converted to thermal energy. When the gas cloud collapses sufficiently it becomes hot enough to emit infrared radiation. This causes electrons to be stripped off the hydrogen atoms and the atoms eventually become hydrogen nuclei (i.e. protons). This causes the whole mass of the cloud to be converted into a mixture of positive ions and negative electrons called Plasma. At this stage the gas cloud can be called: a Protostar.

Collisions between particles become increasingly energetic as the gravitational contraction continues. If the mass of the cloud is high enough, eventually an ignition temperature of about 10 million Kelvin is reached, which gives the hydrogen nuclei sufficient energy to overcome electrostatic repulsion and join together to start the process of nuclear fusion. This process releases a large amount of energy owing to decrease in potential energy due to strong nuclear force. This maintains or increases the core temperature of the gas clouds so that fusion reactions continue. At the ignition temperature, the hydrogen nuclei fuse to form stable helium. The overall reaction involves four hydrogen nuclei fusing together to form a single helium.
As soon as the nuclear fusion process initiates, the gas cloud can be termed as a star. The core of a star is a fusion reactor. Iron is the largest nucleus that can release energy on formation in this way. When the helium in the core of the stars is used up to form heavier elements, the star collapses on itself to become a white dwarf star. This can be marked as the death of the star.

A White Dwarf (Left)

Stars continue shocking us as we explore and understand more plausible theories that unveil secrets of their origin, evolution and death. Our knowledge of celestial objects is still at its infancy. Until we get the exact and most accurate information that define the existence of all celestial bodies from black holes, planets to stars correctly, I suppose it is safe to sing-

      “Twinkle twinkle little star;
How I wonder what you are?”

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By Mahmud Hasan
Aftermath Publications
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The Aftermath Publications, Issue 2
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How to Get the Perfect Date?

No folks Aftermath hasn’t entered the matchmaking business but remains your ever so humble science e-magazine. This article is actually based on the ingenious method that tells you the age of a host of things from a mummy to a dinosaur bone or perhaps the age of the antique clay pot on your display shelf. This scientific process is known as radiometric / radioactive dating. There are number of types of dating from uranium dating to C-14 dating. They are categorized by the time period to which they can reliably confirm dates of objects, formation of geological features or even bodies of ancient people. The C-14 dating was the first convincing dating procedures that worked on matter which was once living. The method was developed immediately following World War II by Willard F. Libby and coworkers, and has provided age determinations in archaeology, geology, geophysics and other branches of science. Radiocarbon determinations can be obtained on wood; charcoal; marine and fresh-water shell; bone and antler; peat and organic-bearing sediments, carbonate deposits such as tufa, caliche, and marl; and dissolved carbon dioxide and carbonates in ocean, lake and ground-water sources.
C-14 is created when cosmic rays from the far reaches of space strike nuclei to produce neutrons; these in turn bombard nitrogen atoms to produce C-14. This C-14 is radio active in nature and combines with oxygen in the atmosphere to form CO2 and thus enter our living cycle.

Archaeologists and scientists use this radioactive quality to their advantage by measuring the activity from the sample substance and
comparing it to the equilibrium level of living things  they can determine the time that has passed. Since all life on Earth is made of organic molecules that contain carbon atoms derived from the atmosphere, all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues.
Once an organism dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 present in the material decreases, and the ratio of C-14 to other carbon atoms declines. In terms of radio carbon dating the fewer C-14 atoms in the sample the older the sample is. The rate of decay of C-14 is pretty steady.

The half life of C-14 is 5730 years. What this means is that half of the C-14 has decayed after 5730 years. Then half of the remaining C-14 or one fourth of the original amount decays in the next 5730 years. After about 50,000 years the amount of C-14 still present in the sample becomes immeasurable. Carbon-14 decays with a half life of about 5730 years by the emission of an electron of energy 0.016 MeV. This changes the atomic number of the nucleus to 7, producing a nucleus of nitrogen-14. At equilibrium with the atmosphere, a gram of carbon shows an activity of about 15 decays per minute.
The low activity of the carbon-14 limits age determinations to the order of 50,000 years by counting techniques. That can be extended to perhaps 100,000 years by accelerator techniques for counting the carbon-14 concentration.

The accelerator technique works with the help of a cyclotron  accelerator working in unison with mass spectrometers .

While radiocarbon dating is a good method of dating fairly recent prehistoric objects, other techniques must be used to date materials older than 50,000 years. These methods include other absolute dating techniques that are similar to C-14 dating methods. Elements other than C-14 can be used in absolute dating techniques.

In this list of radioactive dating processes are:


Samarium-neodymium dating method
This involves the Alpha-decay of 147Sm to 143Nd with a half life of 1.06 x 10^11 years. Accuracy levels of less than twenty million years in two-and-a-half billion years are achievable.

Potassium-argon dating method
This involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the blocking temperature is fairly low in these materials, about 125°C (mica) to 450°C (hornblende).

Rubidium-strontium dating method
This is based on the beta decay of rubidium-87 to strontium-87, with a half-life of 50 billion years. This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples. Blocking temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample.

Uranium-thorium dating method
A relatively short-range dating technique is based on the decay of uranium-238 into thorium-230, a substance with a half-life of about 80,000 years. It is accompanied by a sister process, in which uranium-235 decays into protactinium-231, which has a half-life of 34,300 years.
While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments, from which their ratios are measured. The scheme has a range of several hundred thousand years.

These dating techniques can’t exactly pinpoint the date an event occurred. But they can give us a close approximation as to when the event might have taken place. So now u too have learnt the way to get the perfect date.
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By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 2
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O Radio, O Radio, What Art Thou?

That’s right this time around I will look into our friend in solitude our life saver in desperate times, the “Radio”. The radio is like the nitro that speeded up the telecommunication industry and allowed us to get rid of those hideous wires.
The story is some what like this, after the discovery of radio waves in 1888 an Italian genius named Marconi got a bright idea. The idea was to use radio waves to communicate .This made Marconi one of the pioneers in wireless radio communications. Marconi was successful in introducing radiotelegraph to the world. The importance of the radiotelegraph became more evident when operators from Marconi’s company were the ones to signal in for help which saved around 700 lives during the Titanic wreck. The radiotelegraph didn’t look anything like the radio sets of today. The telegraph was far away from commercial purpose radios as it was able to only communicate in Morse code.

But soon enough Morse code was replaced by speech and music with the introduction of the crystal radio sets around the early 1900s. The credits for this invention goes to an array of scientists as they combined their magical ideas to give us the first radio sets that were able to receive music and speech. The crystal radio sets didn’t require any kind of power supply the radio waves were enough to power up these babies.

1922 Crystal Radio

The crystal radios contained crystals of galena or pyrites which acted as detectors much like the diodes of today. The crystal radios did give sound but quality of the sound needed some fixing up. That’s when the thermionicvlave entered the picture. The thermionicvalves were also known as vacuum tubes. The valves emitted electron after being heated up. They allowed inventors to switch amplify or modify electrical signal by controlling the electron flow and replaced solid state diodes.

Though the valve radios gave quality sound they didn’t appease the users because of their heavy and ugly looking bodies. It was around 1930s that companies like Marconi-phone started building radios that complemented the furniture. This fashionable trend took off from that time onwards with radios. New models of radios had press buttons to preset channels and wooden or metallic exteriors were replaced by bakelite exterior. No the radio wasn’t ugly any more but had changed into a work of art.

A Two Valve Radio 1924

However, the biggest break through in the industry came with the advent of transistors. Using transistors instead of valves in radios reduced power consumption and allowed the use of lighter batteries. In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much larger than the controlling (input) power, the transistor provides amplification of a signal. The transistor is the fundamental building block of modern electronic devices like the radio. Transistors paved the way for portable radios which hit the market with a bang and the people, well they just fell in love with the cute radio sets.

The first commercially successful transistor radio was the Sony TR-55 (as shown in the picture on the right), introduced in 1955.

The radios after this just kept coming in all different sizes and designs. In 1933 Trevor Baylis was watching a program about AIDS in Africa, and realized that many people in developing countries had no radio (and so had limited access to health information) because they had no mains electricity.

He developed the wind-up radio. Windup radio is a radio that is powered by human muscle power rather than batteries or the electrical grid. In the most common arrangement, an internal electrical generator is run by a mainspring, which is wound by a hand crank on the case. Turning the crank winds the spring, and a full winding will allow several hours of operation. The wind-up radio was succeeded by the digital radio that received signals as digital code ensuring clearer sound Because of the way in which the signal can be compressed, more radio stations can be transmitted using the same range of frequencies (‘bandwidth’).

The digital signal includes information about the channel, making it easier to ‘tune in’ (there is no need to remember the frequency). A display on the radio can show the program, the name of the track currently being played, email addresses, up to the minute sports results or competition details, making it more informative.

The development of IC circuits was like a blessing from GOD as it allowed the development of smaller and cheaper and well designed radios. The ICs of today can hold a number of transistors, resistors capacitors all in a tiny amount of space. Thus people know can enjoy the radio even in the poorest parts of the world. The development of the radio was truly amazing from the huge radiotelegraphs to the modern day handheld digital radios. Thanks to a large number of scientific discoveries and scientists who combined to give us our pal in sunshine or rain the Radio set.
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By By Tahsin Uddin Mullick
North South University, Dhaka, Bangladesh
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The Aftermath Publications, Issue 2
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The Fifth Force

The work of a Hungarian scientist Roland von E'otv'os in the early 20th century involved testing the principle of equivalence, a postulate of Einstein's which stated that gravity affecting an object is independent of their composition. This principal is one of the fundamental assumptions of Einstein's General Theory of Relativity and naturally, could not be wrong, E'otv'os declared a null experiment since he discovered an error in his calculation.

And as almost everything in Physics is discovered from “mistakes”, Dr. Ephraim Fishbach and his fellow Physicists at Purdue University set out to prove the existence of a fifth force, related to hypercharge, opposing the force of gravity. The range of this force, they figure is from a few millimeters to cosmic lengths. Even though it's not infinite as gravity, it's as weak as gravity. And thus it is difficult to experiment with. Nonetheless, working with E'otv'os results and re-performing his “mistaken” experiment Fishbach and friends seek to find the effect of this illusive force. So much so that the Physicists have to perform their experiments a kilometer below the surface to find minimal traces of it.

A solid proof of the this force seems to be nowhere in sight and many predict that the effect of its discovery would not be more than causing publishers to release new editions (which they are always happy to) so that students may learn of a new force along with the existing four and find it harder to tell which is which on tests and exams.

It's also unlikely that this fifth force would disprove General Theory of Relativity because it seems to be so insignificant, but I could not help but hope it does. I mean, have YOU read that theory? It's mind blowing, and I am no Einstein.
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By Kowsheek Mahmood
Ryerson University, Toronto, Canada
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The Aftermath Publications, Issue 2
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