New answers tagged

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The density of water (and other fluids) depends both on the pressure and the temperature. A graph for water is here: You may see that at 1 bar (1 atmosphere), the density is highest around 4 °C. That's the conditions where the density reaches the nice 1,000 kilograms per cubic meter. Water contracts when it gets warmer than that, but also when it gets ...


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Sunlight, made up of a mixture of all colors, scatters when it passes between materials, each with a different refractive index, in this case water and air. The water in the river only meets the air at one surface, but the droplets in the air/water mixture contains millions of surfaces. This combination scatters the light more so it appears white ...


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Theoretically there is nothing wrong with your experiment. But I doubt you could succeed. Firstly, how would you prevent air currents from creating water waves that spoil your measurement? A light source at one end of the pool will heat up the water and cause turbulence. This could spoil your measurement because of scintillation of the light beam in the ...


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If you do blow then this helps vapor to go away and make free space for the next portion, as you said. That's why blowing makes evaporation faster.


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When you say "pressure", I think you are probably referring to something like "the height to which the water shoots when you operate the fountain". There are actually two things that affect this: The pressure of the water supply. Any obstruction to the pipe (such as corrosion). As a thought experiment, imagine that you have a completely clear pipe except ...


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When you add salt to water, sodium chloride dissociates into sodium and chlorine ions. These charged particles alter the intermolecular forces between water molecules increasing the boiling point. The temperature needs to be increased about one half degree Celsius for every 58 grams of dissolved salt per kilogram of water.


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There is a pump somewhere upstream in the system to provide water pressure. Apparently it cannot maintain exactly needed pressure but alternatively goes start-stop depending on actual pressure. Once the pump started it delivers pressure as 'high' adjusted, then stops. Then pressure slowly gets down as the water is taken out so when pressure reaches certain ...


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Old pipes get rusted or otherwise clogged by different stuff, such as salts. This will increase the friction of the water flow, resulting in a reduced pressure. The longer the pipes the larger the effect. I do not see any other solutions than to change the clogged pipes, assuming first that you can find which one are the clogged ones (iron pipes instead of ...


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For the hypothetical case of a thermally perfectly insulated system, I'm sure you can work out yourself from the specific heat and the enthalpy of fusion for water. Given that the enthalpy of fusion (330 kJ/kg) and the specific heat of ice (2 kJ/kg-K) have a ratio of 165 K, and you need the entire ice bucket to stay below the melting point, and your 20:1 ...


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If the mouth of the bottle is small (e.g., a wine cork with drilled hole for a drinking straw), water indeed won't flow out. Would you also wonder why the water doesn't stay in an upside-down bucket (the limit case for a bottle with a very wide mouth)? What happens is that air enters through the mouth with a volume equal to the volume of water that leaves ...


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You are just seeing differently illuminated clouds, as should be clear from this picture of an aircraft flying over a thunderstorm: Clouds are made of water droplets or ice crystal, which are transparent. When light is incident upon a cloud, it is scattered at the same wavelength (a process known as Mie scattering). This means that it remains of the same ...


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You have a 2 liter rigid container, featuring 1 liter of liquid water and, above it, one liter of a mixture of air and water vapor all at 1 atm. The temperature is 20 C, and the partial pressure of the water vapor in the head space is the equilibrium vapor pressure, so that the system is at equilibrium. This is the initial thermdynamic equilibrium state of ...


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Let's say that you have a vessel containing water and air and you start heating it. The temperature of the water and air inside will start to rise and so will the pressure, because the air would like to expand (but volume is fixed and water is almost incompressible). Since the boiling point of a substance depends on both pressure and temperature (for example ...


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Based on the page linked in the comments, the answer seems to be the following: (1) The height of the puddle does not depend on the material of the surface so long as the surface is nonwetting. (2) If the amount of water is large then it makes no difference, but if the amount is small, such as a droplet, then the contact angle will become significant and ...


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I am not sure if I could understand your meaning. I think you ask about a situation that the water phase changes from liquid to the gas without passing across two phase region. If the pressure is greater than the critical pressure, then there is no distinct phase-change (boiling) process. You can see this as below figure from “THERMODYNAMICS An Engineering ...


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If you put earthen pot in water before water inside pot reaches surface, then Yes, cooling will become faster. For instance, your hot utensil cools when plunged in water. But, final temperature of water inside pot is independent of above two ways of cooling.


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I guess your question is how to increase evaporation amount because the time is the droplet traveling time. To increase evaporation amount without changing air condition, followings can be considered. reduce droplet size: the evaporation rate is proportion to $\frac {1}{D^2}$, where D is droplet diameter. increase droplet speed: this can increase ...


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I guess the puzzle is to transfer heat out to surrounding and, at the same time, do work to the surrounding. This doesn't violate the first law for sure as the energy is conserved by decreasing internal energy. And this doesn't violate the second law of thermodynamics as well.


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As @Tweej suggests, it's because of water solubility. Because water molecules are quite polar, most things that are charged or polar are soluble in it (i.e.~"hydrophilic"). When a coffee stain dries up, the residue sticks to the surface. But when water is applied, it will readily mix with the water, and more easily be removed. Fats and oils are ...


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Consider the water liquid at its freezing point. When water freezes its internal energy goes down - bonds are made. The decrease in internal energy is equal to the heat removed from the water and the work done by the water in expanding against its surroundings.


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There is no inconsistency. The first law of thermodynamics tells you that during any process the internal energy $U$ of any simple compressible system will satisfy $\Delta U = W + Q$ where here $W$ is the heat received by the system and $Q$ the heat received by it. Upon changing from water to ice, the part of the system that undergoes the phase change does ...


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It does work because it operates like a Heat Engine where the energy travels from something with higher energy (water) to something with less energy (air) to create the work done by the ice. The air has to be colder than the water and below 0C in normal conditions for the water to even freeze. It is just another Heat Engine-like working.



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