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200px|thumb| [[sublimation (chemistry)|Sublimation]] of dry ice when placed on the surface of water at room temperatureDry ice, sometimes referred to as "Cardice" or as "card ice" is the solid form of carbon dioxide.
Dry ice is used as a cooling agent. Moreover, for some applications, the convenience of its sublimation "into thin air," in contrast to the melt-water left by warming water ice, may outweigh other costs.
At temperatures above -56.4|C|F|1 and pressures below 5.13 atm (the triple point), changes from a solid to a gas with no intervening liquid form, through a process called sublimation. The opposite process is called deposition, where changes from the gas to solid phase (dry ice). At atmospheric pressure, sublimation/deposition occurs at -78.5|C|F|1.
The density of dry ice varies, but usually ranges between about 1.4 and 1.6 g/cm3 (87â€“100 lb/ft3). The low temperature and direct sublimation to a gas makes dry ice an effective coolant, since it is colder than water ice and leaves no residue as it changes state. Its enthalpy of sublimation is 571 kJ/kg (25.2 kJ/mol).
It is generally accepted that dry ice was first observed in 1834 by French chemistCharles Thilorier, who published the first account of the substance. In his experiments, he noted that when opening the lid of a large cylinder containing liquid carbon dioxide, most of the liquid CO2 quickly evaporated. This left only solid dry ice in the container. In 1924, Thomas B. Slate applied for a U.S. patent to sell dry ice commercially. Subsequently, he became the first to make dry ice successful as an industry. In 1925, this solid form of CO2 was trademarked by the DryIce Corporation of America as "Dry ice", thus leading to its common name. That same year the DryIce Co. sold the substance commercially for the first time; marketing it for refrigerating purposes.
Dry ice is easily manufactured. There are common steps taken in producing dry ice. First, gases containing a high concentration of carbon dioxide are produced. Such gases can be a byproduct of some other process, such as producing ammonia from nitrogen and natural gas, or large-scale fermentation. Second, carbon dioxide-rich gas is pressurized and refrigerated until it changes into its liquid form. Next, the pressure is reduced. When this occurs some liquid carbon dioxide vaporizes, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. As a result, the extreme cold causes the liquid to solidify into a snow-like consistency. Finally, the snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.
Dry ice is typically produced in two standard forms: blocks and cylindrical pellets. A standard block weighing approximately 30 kg is most common. These are commonly used in shipping, because they sublimate slowly due to a relatively small surface area. Pellets are around 1|cm|1|abbr=on in diameter and can be bagged easily. This form is suited to small scale use, for example at grocery stores and laboratories.
The most common use of dry ice is to preserve food, using non-cyclic refrigeration.
It is frequently used to package items that need to remain cold or frozen, such as ice cream or biological samples, without the use of mechanical cooling.
Dry ice can be used to arrest and prevent insect activity in closed containers of grains and grain products, as it displaces oxygen, but does not alter the taste or quality of such foods. For the same reason, it can prevent or retard food oils and fats from becoming rancid.
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Answers:Two constants you need, and their units will tell you how to solve the problems. Specific heat of water 4.184 J/(g K) heat of fusion 334 J/g 1) 334 J/g x 35g = 11,690 J notice the g's cancel and we are left with J 2) 4.184 J/(g K) x 35g x 20C = 2,929 J again g's cancel, as do temperatures.
Answers:Ice can turn to water wapour by sublimation (the direct change from solid state to gas state). But I think it cannot just turn into air...
Answers:My first thought would be a leak that only drips (releases pressure) when the pipes expand from the heat of the water. If you're using something other than copper, than I couldn't tell you. I would suggest calling out a plumber and making sure your friend didn't screw things up. BTW, the cold and hot lines have separate pipes, so even if the hot doesn't flow, the cold would.
Answers:let there be (m) kg of ice. it is mixed with 2kg water at 25C. >>> resulting stage is Ice-Water i.e water at 0C or water could just melt the entire ice. final temperature = 0C heat lost of water = heat gained by ice in melting -------- (1) 2 * 4181.3 *[25 - 0] = m [334.88*1000] m = 0.624 kg ========================= water available = 2 + 0.624 kg = 2.624 kg ==================== in equ(1) we have assumed that the ice-water mixing container is isolated from the rest of universe > that is when no heat escapes from the system, and is fully utilised in melting the given ice. thus its an adiabatic change, so change in entropy of the process (dS) = 0