What is the difference between  moisture content & water activity of a food item?
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Simple web search\n\nhttp://drinc.ucdavis.edu/dairychem4.htm\n\nhttp://www.fda.gov/ora/inspect_ref/itg/itg39.html
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Soil absorbs moisture. It has small openings and the water gets in the small holes. The cohesion and adhesion of the water constitute a force that keeps the water in the soil, to a certain extent.
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Density is measured by weight per unit of volume, such as the density of water is 62.4 pounds per cubic foot.\n\nViscosity is a measurement of the rate at which a liquid flows or more accurately, its resistance to flowing. Water has low viscosity, honey has high viscosity.
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Low.\n\nHigh pressure tends to be dry, while lows suck moisture in.
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It depends largely on the environemnt. Lipids are better storage media in hypotonic or isotonic conditons because they have no osmotic effect. In hypertonic or just plain dry conditions starches and sugars are beneficial because they aborb and retain water.
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It's no use trying to find that out. Those conditions are to be fully controlled to get "non-colored" products.\nAnd be careful with what you use in food products!!
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yes, moist air has more water molecules than dry air.
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hmmm, interesting, I should imagine it's related in some way to the specific heat capacity of an egg vs that of water, as well as the entropic changes involved with the egg yoke and egg white denaturing....need to think more about this\n\nedit...I don't see the full relevance of this equilibrium argument, it merely describes the time taken for heat to permeate the egg, nothing about itsd heat capacity relative to water. That all the water is the same temp is due to its thermal conductivity. Granted in a practical environment time is a factor, because you would be losing heat to the environment from the system whilst keeping the water boiling. I think we need to lay down some assumptions. What kind of egg are we delaing with and is it to be hard or soft boiled (changes of state)
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It appears that the constants are calculated at one condition (dry,wet,etc) whereas the effective is closer to reality.  See\n\nhttp://www.pnas.org/cgi/content/full/102/45/16293
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It also depends on the moisture content and the humidity I suppose.
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It will vary greatly depending on how the vegetable was grown and harvested.  The best way to find out (perchance) would be to weigh it, then dehydrate it and weigh it again, noting the difference.
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These are physical changes.  The matter simple changes state, depending on tempature.  Also see evaporation.
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The humidity makes a difference. I've had bread for a week that never had mold. When it gets humid I'm lucky to keep it for 4 days.
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specific heat capacity : \n  * Grass contain more water content than beach sand. The grass evaporate the water and make itself cool.\n  * Sand has more specific heat capacity, it absorbs more heat and retains it.
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bulk density /(moisture content - 1) is equal to dry density.\n\nBulk density = weight of wet soil collected from the hole / volume of the hole\n\nVolume of hole = wt. of sand transferred into hole / bulk density of sand\n\nWeight of sand = Total wt of sand in cylinder before pouring - (wt of sand in cylinder after pouring+wt of sand in cone)\n\nBulk density of sand and wt. of sand in cone are determined in laboratory. for details on that write to nobodyat34@yahoo.co.in
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The food is "burned" in a bomb calorimeter.  The energy given off by the food causes the water to change temperature.  The change in temperature of the water allows us to calculate the calorie value of the food sample.
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That's a very interesting question (and boiling as mentioned by other posters is only part of the story).  Let's take evaportaion of water from a bath towel in a shower room as an example.  When you "dry" yourself with a fresh towel it gets wettter while you get dryer.  But the towel can not make you totally dry.  It easily removes the beads of water and excess layers of water but leaves you with a final surface film of water that can not be removed by the towel.  This water film must evaporate.\n\nIn the towel itself, water molecules (H2O) absorb energy from the air by collision with numerous air molecules.  Some of the molecules gain enough energy to vibrate and separate from the rest of the water and enter the air to join any present water vapor.  At this point, water molecules can leave and re-enter the towel's moisture and the net gain or loss of water will depend on the relative humidity in the room.  At 100% relative humidity the towel will theoretically never "dry" unless condensation is being removed somewhere from the room.  At zero relative humidity, the towel dries very quilckly because there are a lot of molecules trying to escape but few trying to return.  High temperature, especially at low humidity, can speed up the process by supplying more energy to the water molecules in the towel.\n\nIf the towel is folded, moisture will evaporate from one fold and re-enter another fold slowing up the enttire process.  The more you expose surface area the faster the towel will dry (and the less time there will be for bacteria to grow!).\n\nIn a glass jar of canned tomatoes, water molecules are constantly evaporating from the liquid surface and re-entering it at the same rate without any net change.  The jar is under a partial vacuum because air was excluded and the trapped vapor is saturated with moisture to the same extent air would be saturated with moisture at the same temperature because the exchange of water molecules occurs due to its own energy levels (perhaps supplied by collisions with air molecules) but not influenced by any interference by the air molecules.\n\nWhen water (or sweat or gasoline, etc.) evaporates from your skin, it feels cool because it is taking energy from your skin to evaporate, taking the latent heat of vaporization which is significant.