| Soap Bubble |
Article Index for Soap |
Website Links For Soap |
Information AboutSoap Bubble |
| CATEGORIES ABOUT SOAP BUBBLE | |
| fluid dynamics | |
| minimal surfaces | |
| toys | |
| bubbles | |
|
A soap bubble is a very thin Film of Soap Water that forms a hollow Sphere with an Iridescent Surface . Soap bubbles usually last for only a few moments and then burst either on their own or on contact with another object. They are often used as a children's plaything, but their usage in artistic Performances shows that they can be fascinating for adults too. Soap bubbles can help to solve complex Mathematical problems of Space , as they will always find the smallest surface area between Points or Edges . PHYSICS Surface tension and shape , 2nd third of 18th Century .]] A bubble can exist because the surface layer of a Liquid (usually water) has a certain Surface Tension , which causes the layer to behave somewhat like an Elastic sheet. However, a bubble made with a pure liquid alone is not stable and a dissolved Surfactant such as soap is needed to stabilise a bubble. A common misconception is that soap increases the water's surface tension. Actually soap does the exact opposite, decreasing it to approximately one third the surface tension of pure water. Soap does not ''strengthen'' bubbles, it ''stabilizes'' them, via an action known as the Marangoni Effect . As the soap film stretches, the concentration of soap decreases, which causes the surface tension to increase. Thus, soap selectively strengthens the weakest parts of the bubble and tends to prevent them from stretching further. In addition, the soap reduces Evaporation so the bubbles last longer, although this effect is relatively small. Their Spherical shape is also caused by surface tension. The tension causes the bubble to form a sphere, as a sphere has the smallest possible Surface Area for a given Volume . This shape can be visibly distorted by air currents, and hence by blowing. If a bubble is left to sink in still Air , however, it remains very nearly spherical, more so for example than the typical cartoon depiction of a Raindrop . When a sinking body has reached its Terminal Velocity , the Drag Force acting on it is equal to its Weight , and since a bubble's weight is much smaller in relation to its size than a raindrop's, its shape is distorted much less. (The surface tension opposing the distortion is similar in the two cases: The soap reduces the water's surface tension to approximately one third, but it is effectively doubled since the film has an inner and an outer surface.) Freezing Soap bubbles blown into air that is below a Temperature of −15 °C (5 °F ) will freeze when they Touch A Surface . The air inside will gradually Diffuse out, causing the bubble to crumple under its own weight. At temperatures below, say, −25 °C (−13 °F), bubbles will freeze in the air and may shatter when hitting the ground. When, at this low temperature, a bubble is blown with warm breath, the bubble will freeze to an almost perfect sphere at first, but when the warm air cools and thus is reduced in volume there will be a partial collapse of the bubble. A bubble, blown successfully at this low temperature, will always be rather small in size: it will freeze quickly and continuing to blow will shatter the bubble. Merging When two bubbles merge, the same physical principles apply, and the bubbles will adopt the shape with the smallest possible surface area. Their common wall will bulge into the larger bubble, as smaller bubbles have a higher internal Pressure . If the bubbles are of equal size, the wall will be flat. At a point where two or more bubbles meet, they sort themselves out so that only three bubble walls meet along a line, separated by angles of 120°. This is the most Efficient choice, again, which is also the reason why the cells of a Beehive use the same 120° angle, thus forming Hexagons . Only four bubble walls can meet at a point, with the lines where triplets of bubble walls meet separated by 109.47°. |
|
|