Why does water in a metal canteen stay cooler if the cloth jacket surrounding the canteen is kept moist?
407211
The evaporation of the water removes some of the heat from the catneen and it's contents.
619332
The container, because it's in contact with the outside environment, is a heat sink/source and thus it will be at a slightly lower or higher temperature than the solution.
71035
Not 100% sure. But I think its because the air inside isn't moving. The air inside is stationary, while it is continuously circulating outside, which causes changes in the temperature. IMHO
25468
Prevents it from boilig or freezing
775810
Pudding develops a film on its surface because water evaporates from the surface of the pudding, leaving the surface drier than it was before.  So the film is just dried out pudding.\n\nIf the pudding is covered, water still evaporates out of the pudding, and as the air above the pudding absorbs this water, some of it condenses onto the plastic wrap.
596740
Like everyone else said, it makes the drink cooler. However, this is because heat is transferred in an attempt to achieve equilibrium. In this case, the equilibrium would be between the temperature of the ice and that of the drink. Because the average temperature of the drink is higher than that of the ice, heat flows out of the drink and into the ice, slowly levelling the temperature.
113741
This is called evaporative cooling.\nThe water is cooler than your skin and absorbs this excess heat until it reaches evaporation temperature. As the water evaporates it releases this heat into the air which must be cooler than your body for this process to work. This is why sweating helps cool the body. The hotter and more humid the air temperature, the slower the evaporative cooling effect takes place.
46526
it doesnt, however the energy is lost faster in hot water than in cooler water.  The rate at which all water freezes is the same.
281054
Because it is water base and water will evaporates.
136240
I think kurdiatcha needs a hug\n\nThe concept you are questioning is called "specific heat capacity" liquid water has a very high specific heat so it would take longer to reach room temp.
403230
It takes quite a lot of energy for water to change phase.  Steam actually contains much more energy than does boiling water, therefore it burns far worse when it comes in contact with human skin.\n\nSee the link below.  You can actually do the math to confirm this -- it takes 100 cal/gm to heat water from 0 to 100 degrees C, but 539 cal/gm to change that water into steam.  So ten grams of water at 0 degrees C absorbs 1000 calories to boil but nearly 6400 calories to turn completely into steam.\n\nThat's a lot of heat.\n\nIn rebuttal to some of the other answers, burns are caused (I believe) by heat convection -- that is, the hot substance in direct contact with the skin, transferring its heat to the skin cells and damaging or destroying them.  Water is more likely to stay in contact with the skin than steam is, because steam is a gas that rises away from the skin.  This is why some people seem to erroneously believe that steam doesn't burn.\n\nHowever if skin comes into continuous contact with steam, it will burn, and quite badly.
651341
High humidity makes the temperature seem warmer.\n\nAlso, when something condenses, as in the water in the clouds, it gives off energy often in the form of heat.
836179
water and oxygen are 2 things which cause rusting..in this case there is lots of water and lots of oxygen in the boiling water plus there is the catalyst of heat..\n\nbut by painting it with aluminium paint the surface of alumnium reacts to form an unreactive strong layer of AL2O3 this protects alumninium from furtherly rusting and the iron or steel behind the aluminium>>>plus they usually do this instead of using completely aluminium pipes because its more economic to use steel and paint with aluminium instead of making aluminium pipes plus steel is much stronger
726971
h2o has a higher specific heat, meaning it takes a greater amount of energy to change the temperature of the h2o than the metal.  That is why it takes a long time for lakes to freez, ect.
503805
It doesn't, and doesn't need too.\nWhat keeps the temperature, stable, isn't the fact that the liquid is hot or cold, it's that it isn't exposed to the atmosphere, that will change it.\nDue to the vacuum inside the bottle, it slows the transfer of heat. Both from the inside and the outside.\nIt won't keep the temperature the same for ever, there is always some heat loss, particularly, if you open the bottle.\nBut it will keep it hot of cold much longer, than it would, without the vacuum.
425548
A desert cooler takes advantage of very low relative humidity to acheive its cooling properties.   Rather than relying upon a refrigerant system (i.e. Freon) with a compressor to circulate the refrigerant, a desert cooler uses evaporation of water to remove heat.  With a low relative humidity, water can evaporate quite rapidly, taking a lot of heat energy along with it.  \n\nThere are a variety of different techniques to exchange and remove heat from the air.  One that is used in less arid climates is called a swamp cooler, in which water is pumped from a pond, through a heat exchanger and then back through a fountain in the pond.  The fountain aids in the evaporative process, helping to keep water cooler.  \n\nWhile a desert cooling system may not be able to develop as cold of temperatures as a refrigerant-based system, it still can effectively reduce the air temperature, and do so using less electricity since a compressor is not required to run.
674634
Heat is transferred by conduction, convection and radiation. In medium-temperature applications radiation would only be a small part of the total, and an opaque material will prevent radiative escape of heat in any case. Conduction and convection are minimized by the structure of a typical insulator in addition to the material properties mentioned in the first answer. Styrofoam, for instance, consists of very thin partitions of styrene plastic which enclose gas-filled bubbles. This means each convection cell or mixing space is small and essentially a small proportion of the total insulation thickness, so you don't have the coldest internal gas mixing with the hottest gas. Conduction is low because gas conducts heat more slowly than a solid. The conduction path through the solid styrene is convoluted and of small thickness, both of which minimize conduction. In houses, fiberglass insulation uses similar principles except that the air spaces are connected. This means a larger convection cell potentially exists, but it is baffled by all the glass strands, so circulation and mixing are much slower and smaller-scale.