Supercooling and instant freezing of purified water

Instant Freeze Water

Instantly Frozen Water Experiment (Poulter, N.d.)

There is a common phenomenon that has been experienced by many people. During the winter, if you leave a bottle of water in a car, garage, or other cold place overnight then something quite interesting can happen -- then the cap is opened, the liquid can freeze instantly. This experiment reproduces this phenomenon using a few simple materials and also explains the science behind what is going on relative to the "instant freeze water." "

The materials needed for the experiment include (Wells, 2013):

Seltzer water -- flavored or plain in plastic bottles. Do not use glass bottles as the liquid may accidentally freeze in the bottle, causing it to explode.

Large bucket

Ice

Rock salt

Thermometer

Explanation

Everyone knows that water freezes at 0 °C - or does it? When water freezes, it needs a nucleus in order for the solid crystals to form and become ice and water is typically full of particles and impurities which have no problem kicking off the crystallization process; however, purified water by definition doesn't have those impurities and with nothing for the water molecules to latch onto, purified water can be supercooled as far as -40°C (Winter, 2014). Once the solution is supercooled, then the solution is simply waiting for something to allow it to begin freezing. Opening the bottle allows carbon dioxide bubbles to form and these bubbles provide a place for the nucleation of the ice crystals to begin occurring (Poulter, N.d.).

Liquid water is a network of water molecules (each with two hydrogen atoms and one oxygen atom) held loosely together by what is called hydrogen bonding, which is somewhat like static cling and depending on its temperature and pressure, water ice has 16 different crystalline forms in which water molecules cling to each other with hydrogen bonds (University of Utah, 2011). Researchers explain that "what makes water so strange is that the way liquid water behaves is completely different from other liquids. For example, ice floats on water while most solids sink into their liquid forms because they are denser than the liquids (University of Utah, 2011)." However, one of the most interesting facts about water is alter its freezing point by preventing it from forming the first seed of ice.

For generations a very simple and abundant substance has posed many mysteries to researchers. While most people have learned sometime in school that 0 degrees Celsius is the freezing point of water, there are actually many variables that can affect the actual freezing point. Many of these variables can allow the freezing point of water to drop far below the previously recognized threshold and become what is referred to as super cooled. Scientist have recently made some breakthroughs in understanding the absolute lowest freezing point that water can reach. University of Utah chemists used computers to determine that water, which doesn't necessarily become solid at its 32 degrees Fahrenheit freezing point, actually can get as cold as minus 55 F before it must freeze (University of Utah, 2011).

Figure 2 -Regular ice crystals (red) are mixed with "intermediate ice" (green) near the end of the process of crystallizing from supercooled water (University of Utah, 2011).