Frozen Soap Bubbles
30 August 2018
Blowing soap bubbles has amused children, and adults, for centuries. Lately people have begun blowing soap bubbles in sub-freezing weather. Photograpers Carey Sherrill, Chris Ratzlaff and Adrian Ybarra have recorded the cool effect of cristals moving on the bubbles.
Soap bubbles form when a layer of water molecules gets trapped between two layers of soap molecules. When it's cold outside, the water layer freezes before the soap bubble pops.
To understand freezing soap bubbles, and why water crystals move in the bubble, we need to understand a little bit of science. Water is made of hydrogen and oxygen. Water is a polar molecule, meaning that it has a slightly positive end (the hydrogen), which is attracted to the slightly negative (oxygen) end of another water molecule.
Soap is a long chain of carbon and hydrogen atoms linked together with hydrogen attached to the carbons. Soap molecules have a carbon-oxygen end that is negatively charged. A soap bubble consists of a layer of water, about one one-hundredth of a millimeter thick, sandwiched between two layers of soap molecules. The soap's negative end is attracted to the positive, hydrogen end of the water molecules.
After the water layer has solidified, the air inside the bubble will start to spread out. The colder it is outside, the longer the bubble will retain its shape. The air inside the bubble will diffuse faster if it's warmer and slower if it's colder. If it's very cold out, such as the negative temperatures we've seen this week, the bubbles can form ice crystals. Instead of popping, the bubbles crack after forming into a crystalline structure.
You can sometimes see the air diffusing through the semi-rigid soapy structure. A very similar process happens with balloons and car tires.
A balloon in subzero temperatures deflates because the cold slows down the air molecules inside the semi-rigid structure. When you bring the balloon back into room temperature, it will slowly inflate again. One of the mistakes people do is to inflate their tires without realizing the tire pressure will increase again once the weather improves.
|Written by: Laura Cozzo|