Low surface tension also helps bubbles grow quickly. Measurements showed that the surface tension in water containing the sweetener aspartame is lower than in sugary water, explaining why Diet Coke creates more dramatic fountains than sugary Coke.
Another factor is that the coatings of Mentos contain gum arabic, a surfactant that further reduces surface tension in the liquid. Rough-surfaced mints without the surfactant did not create such large fountains. Mentos are also fairly dense and sink rapidly, quickly creating bubbles that seed further bubbles as they rise.
Crushed Mentos that fell more slowly created puny fountains that only travelled about 30 centimetres. The surfactants in Mentos are found in its ingredients. Primarily, the sugar, aspartame and potassium benzoate included in the candy shell reduce the work it takes to form bubbles in the soda, causing a rapid creation of carbon dioxide bubbles.
These ingredients accelerate the foaming action of the soda very quickly, causing the infamous explosion. Caffeine is also a surfactant, but soda doesn't include enough caffeine for there to be a significant increase in the reaction.
A Mentos candy feels smooth to the touch, but place it under a microscope, and the surface looks rougher than sandpaper. The bumps and cavities on the surface of a Mentos candy increase the surface area that comes in contact with the soda. This causes the candy shell to dissolve faster, distributing more surfactants into the soda, which causes more bubbles.
A string or a stick is immersed into a supersaturated mixture of sugar and water, and crystals of sugar nucleate around the stick.
Without immersing the stick, the crystals will grow eventually, but the stick speeds up the process by providing a surface for nucleation.
This pressure effect of gases and liquids also has a more dangerous aspect as well: when scuba divers go to great depths in the ocean, they are breathing air, or specialized gas mixtures, at four or more times atmospheric pressure. Because of this, nitrogen dissolves into their blood stream in much higher amounts than would happen at the ocean surface. The exploding water in the garbage can demonstrates what happens when a gas, which is confined by pressure, is released suddenly: it expands very rapidly, blowing out everything in its way.
The gas used in this experiment is liquid nitrogen, which was carefully anchored beneath the water. Do not try this at home! Liquid nitrogen should only be handled by experts. Watch the slow-motion video carefully, and observe how the Brute garbage can the blue seamless one deforms during the explosion. At warmer temperature CO2 gas particles and other molecules have more energy. Therefore, the particles move faster and want to escape the liquid they are dissolved in quickly compared to cooler temperatures.
Try cracking open a can of warm fizzy drink and compare it to one just from the fridge! A 2 Litre bottle of coke or lemonade have 8 litres of CO2 dissolved in them. Have you noticed, your fizzy drink has tiny bubbles appearing on the side of the glass at a particular spot? This is because bubbles form on tiny pits on the surface of a container. These imperfections are called nucleation sites.
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