If we try to fill a glass of soda without letting it overflow, we usually notice the bubbles or froth of the drink. As we fill the glass, bubbles form on the surface and these tiny bubbles grow. Reaching a certain size, the bubbles escape from the liquid surface, and vanish into the air. If we put our finger, or a straw into the soda-as most of us did as children- we immediately notice that tiny bubbles of gas form on the object immersed in the glass. Just like in the freezing of water or in the escape of gas from soda, a precise energy exchange occurs at the initial stage of any phase transformation. Completion of any phase transformation - freezing or condensation (clouds transforming to rain)- is impossible without such precise energy exchange. The fact that all these phase transformation occur with precise energy calculations in the best possible temperature ranges to support life is a clear proof that nothing in the universe was created by mere coincidence, and that everything occurs by the command of the Almighty.
We know that everything in the universe obeys the minimum energy principle. If we want to freeze water, all we have to do is to cool it to a temperature below 0°C, and the transition from water to ice begins. Water molecules tend to gather together to form clusters. When five to ten of these molecules bond together, however, a difficulty is encountered. The formation of solid-liquid, solid-gas, or liquid-gas interfaces requires a specific amount of energy. In the beginning, the surfaces of these clusters are quite large as compared to their volumes such that the energy they receive to form an interface is much greater than the energy they release; therefore the state of minimum energy is not reached. To explain this to you in another way: let us assume that we manufacture beads for the production of costume jewelry and garments, and the surface of the beads requires treatment. If the beads we manufacture are smaller than the specific size, they will be more expensive to treat, and therefore will not cover the costs, so only producing beads exceeding the specific size will be profitable to the manufacturer. The main aspect here is actually the size of the beads, so if manufacturing beads which exceed the specific size is simpler and more profitable, rejecting the beads smaller than these specifications would be inevitable.
As in this example, because of their high energy value, the molecular clusters formed initially (embryos) return to a liquid form. Then once again the particles begin to bond, but again the result is the same. An embryo must grow to a certain size for its surface area to decrease in comparison to its volume and thus reduce its energy. This is only feasible when many atoms bond, for only when a sufficient number of atoms join together does the embryo transform into a nucleus, and then begin to crystallize and eventually become solid. Figure 1 shows the transition of homogeneous nucleation. The process called homogeneous nucleation is only possible under certain conditions: the liquid must be at a temperature of around –40 oC for both the transition in the balance of energy, and for the water molecules and atoms to become solid and bond to form a nucleus. If we contain pure water totally motionless in the deepfreeze at approximately –8 oC, we will have supercooled water that has not yet transformed into ice; the temperature between the nucleation and the freezing points, is called supercooling. Supercooling is a metastable condition where liquid or gas remains supercooled without actually becoming frozen, but the slightest intervention or movement can cause the substance to transform into a solid. The tiny bubbles of carbon dioxide in soda is also in a metastable condition, for as soon as the bubbles have the opportunity, they escape from the liquid and vanish into the air. If we immerse a straw or finger into a glass of soda, this forms an added surface, which also facilitates a solid-gas interface, and if we add a teaspoon of sugar to the soda, this induces the drink to froth and bubble at great speed. Water boiled in a saucepan actually nucleates on the wall of the container.
Supercooling is a metastable form of the substance. Every substance or solution has a specific temperature value for cooling. For instance, liquid copper transforms into a solid at 1083 oC. Homogeneous nucleation requires the bonding of 310 atoms, and supercooling to approximately 236 oC.
Under normal conditions, substances which have more than one type of molecule undergo phase transformation known as heterogeneous nucleation. In this case, the atoms form primarily on the walls of a container on particles of impurity, or minute solid particles in the liquid, and this significantly reduces the surface energy barrier for nucleation (Figure 2). So for a moment let us return to the bead example. We have discovered that instead of directly manufacturing smaller beads, it would reduce the costs of decorating the surface of the beads to coat and treat larger beads, so the beads are being produced in this way, thus reducing losses.
Supercooling can occur at temperatures even as high as 2–3 oC, and this is very important. The condensation of water or supercooled water droplets in clouds must reach a specific size and weight in order to fall to the earth as raindrops. Here, the solid microscopic particles combine to form nuclei. Even if the clouds are much lower in temperature, rain cannot form without nuclei. Particles of salt which escape from the sea, sand that rises from the desert, the sulphate released from the ashes of volcanic activity or minute atoms of dimethyl sulphate emitted by certain planktons are driven into the atmosphere by the wind and form nuclei. As the Almighty, the Creator of the universe revealed in Al-Hijr, verse 22 of the Qur’an: “And We send the winds to fertilize, and so We send down water from the sky, and give it to you to drink (and use in other ways)” indicating that one of the duties of the wind is fertilization. Even the particles in smoke released irresponsibly by humans from industrial chimneys, or from car exhausts form nuclei that eventually transform into rain (Figure 3).
During the foundry process, solid substances are added to liquid metals for certain purposes, such as enabling metal to set more rapidly, or increasing the metal’s durability. When liquid metal is cooled, its atoms form nuclei on microscopic solid impurities. These nuclei increase in size and assemble into groups called grains. The irregular zone between these groups is known as the grain boundary. The grain boundary forces the compressed atoms to move and weld, thus increasing the durability of the metal. This method known as infusion or grain contraction ensures an increase in the formation of nuclei, and also in the durability of the metal. Cloud seeding, a topic which mainly comes to light when there is a lack of rain, is actually inducing the clouds to form artificial nuclei that will in turn produce rain.
Some creatures on earth protect themselves with mechanisms bestowed by their Creator, and one of these creatures is the wood frog. As the water in its cells begins to freeze, the antigel protein found in its blood surrounds the formation of nuclei, and prevents the nuclei from increasing in size. The frog remains frozen and motionless until the temperature increases. If we touched a wood frog in this condition, its cells too would freeze suddenly, and the frog would die. It is impossible for a frog to know how to cool to the point of freezing, and nucleate. It is also impossible for a frog to adapt to such a mechanism because this would require practice and experience, which would of course be deadly. Therefore, is the frog’s ability to freeze, and its process of nucleation not a clear indication of the providence and blessing of God the Almighty?
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