An old style mercury barometer consists of a vertical glass tube about 1 cm in diameter partially filled with mercury, and with a vacuum (called Torricelli's vacuum) in the unfilled volume (see diagram to the right). Notice that the mercury level at the center of the tube is higher than at the edges, making the upper surface of the mercury dome-shaped. The center of mass of the entire column of mercury would be slightly lower if the top surface of the mercury were flat over the entire crossection of the tube. But the dome-shaped top gives slightly less surface area to the entire mass of mercury. Again the two effects combine to minimize the total potential energy. Such a surface shape is known as a convex meniscus.
We consider the surface area of the entire mass of mercury, including the part of the surface that is in contact with the glass, because mercury does not adhere at all to glass. So the surface tension of the mercury acts over its entire surface area, including where it is in contact with the glass. If instead of glass, the tube were made out of copper, the situation would be very different. Mercury aggressively adheres to copper. So in a copper tube, the level of mercury at the center of the tube will be lower than at the edges (that is, it would be a concave meniscus). In a situation where the liquid adheres to the walls of its container, we consider the part of the fluid's surface area that is in contact with the container to have "negative" surface tension. The fluid then works to maximize the contact surface area. So in this case increasing the area in contact with the container decreases rather than increases the potential energy. That decrease is enough to compensate for the increased potential energy associated with lifting the fluid near the walls of the container.
If a tube is sufficiently narrow and the liquid adhesion to its walls is sufficiently strong, surface tension can draw liquid up the tube in a phenomenon known as capillary action. The height the column is lifted to is given by:
where
Pouring mercury onto a horizontal flat sheet of glass results in a puddle that has a perceptible thickness. The puddle will spread out only to the point where it is a little under half a centimeter thick, and no thinner. Again this is due to the action of mercury's strong surface tension. The liquid mass flattens out because that brings as much of the mercury to as low a level as possible, but the surface tension, at the same time, is acting to reduce the total surface area. The result is the compromise of a puddle of a nearly fixed thickness.
The same surface tension demonstration can be done with water, lime water or even saline, but only if the liquid does not adhere to the flat surface material. Wax is such a substance. Water poured onto a smooth, flat, horizontal wax surface, say a waxed sheet of glass, will behave similarly to the mercury poured onto glass.
The thickness of a puddle of liquid on a surface whose contact angle is 180° is given by:
where
In reality, the thicknesses of the puddles will be slightly less than what is predicted by the above formula because very few surfaces have a contact angle of 180° with any liquid. When the contact angle is less than 180°, the thickness is given by:
For mercury on glass, γ = 487 dyn/cm, ρ = 13.5 g/cm and θ = 140°, which gives h = 0.36 cm. For water on paraffin at 25 °C, γ = 72 dyn/cm, ρ = 1.0 g/cm, and θ = 107° which gives h = 0.44 cm.
The formula also predicts that when the contact angle is 0°, the liquid will spread out into a micro-thin layer over the surface. Such a surface is said to be fully wettable by the liquid.
In day-to-day life we all observe that a stream of water emerging from a faucet will break up into droplets, no matter how smoothly the stream is emitted from the faucet. This is due to a phenomenon called the Plateau–Rayleigh instability, which is entirely a consequence of the effects of surface tension.
The explanation of this instability begins with the existence of tiny perturbations in the stream. These are always present, no matter how smooth the stream is. If the perturbations are resolved into sinusoidal components, we find that some components grow with time while others decay with time. Among those that grow with time, some grow at faster rates than others. Whether a component decays or grows, and how fast it grows is entirely a function of its wave number (a measure of how many peaks and troughs per centimeter) and the radii of the original cylindrical stream.
The Suite Life on Deck
The Suite Life on Deck was an American television series on Disney Channel. It premiered on September 26, 2008. It is a sequel to "The Suite Life of Zack and Cody". The series is about twin brothers Zack and Cody Martin and hotel heiress London Tipton in a new setting, the SS "Tipton". The group goes to classes at a school on the boat that is called "Seven Seas High". On the boat, they meet Bailey Pickett. Mr. Moseby manages the ship. The ship travels around the world to nations such as Italy, Greece, India, Sweden and the United Kingdom In the places where the ship travels, the characters experience different cultures, adventures, and situations.
The show's first episode premiered on the Disney Channel in the US on September 26, 2008. Around 5.7 million people watched it on the night of its premiere.. The series premiere in Canada was also the most watched series premiere on Family channel. In December 2008, Business Wire reported that the show was 2008's #1 scripted television series for children between the ages 6 to 11 and older children between the ages 9 to 14, beating the older series "Hannah Montana" and "Wizards of Waverly Place" in the ratings.<ref name="Disney Channel/DisneyChannel.com Highlights For 2008"></ref> The show was in the #1 spot for the best rated children's television series for many months. The show has been one of the best 4 live-action television series for many months. Since then, “The Suite Life on Deck” had a large lead in the time slot (Friday 8:00 p.m.), ranking as TV's #1 program among the important children's age groups. The series is also #1 in total viewers on all cable, doing better than #2 rank (Fox News and Nickelodeon) by 800,000 more viewers.
As of August 2009, the highest rated episode of "The Suite Life on Deck" was "Double-Crossed," the second part of "Wizards On Deck with Hannah Montana", three episodes where guest stars from "Wizards of Waverly Place" and "Hannah Montana" came onto the show. It premiered on July 17, 2009 on Disney Channel. The special episode was viewed by more than 10.6 million people. It is one of the highest-rated episodes for a Disney Channel original series.
In early October 2009, the one hour special episode "Lost at Sea" became the most watched episode of the series. It had 7.6 million total viewers. In 2009, the series was the most watched scripted series in the children and older children group of viewers (6-14). The series second season's ratings were 25% higher than the show's season one ratings. The second season has averaged around 5.1 million viewers.
Before the series officially started airing, the first episode named "The Suite Life Sets Sail" was made available as a free download on iTunes. All series have since been made available.
Atmospheric chemistry
Atmospheric chemistry is a branch of science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary field of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology and other disciplines. Research is connected with other areas of study such as climatology.