# Tag Info

1

I believe the 'urban legend' you are referring to is about cooling a bottle when you do not have a refrigerator. On a hot and windy day you could store your bottle in the sunlight, but it would be better in the shade, but if you really wanted to cool the bottle by a few more degrees, the 'myth' says wrap it in wet paper or cloth. During the time when the ...

2

It may actually work, as evaporating liquids need heat to evaporate, and water will somewhat evaporate even in the fridge. I am not sure it works in practice, because the paper also causes an adverse effect, it provides insulation, Hard to tell which effect is dominant. I'm pretty sure that the balance of both effects depends in a very large part on the ...

1

Let's start with the evaporation of water (or sublimation, in this case). Carbon dioxide exists as a gas at normal temperature and pressure. If it is compressed and cooled, you make dry ice. When dry ice heats up, the solid becomes a gas directly (any liquid is from water condensing on the dry ice). This process is called sublimation. Water (or ice) can ...

2

The boiling temperature of a liquid is not the temperature at which it can enter the gaseous state. Rather, it is the temperature at which the saturation vapor pressure $e_s$ is equal to ambient atmospheric pressure. This is why, for example, water boils at lower temperatures at higher altitudes. Furthermore, water is always evaporating. It is also ...

0

All water moleucles contain energy, in accordance with the temperature. Hot water has enough energy to escape the liquid as vapour. Even though a body of water is below boiling point, the molecules with more energy (relative to the body of water),rise to the top and can escape, as vapour Tis easy!

-1

In Science class, my teacher put a flask of water on his worktable, covered it with a glass dome with a rubber rim on it so as to seal the dome to the desk. He then hooked a hose to the dome, the other end to a vacuum device and proceeded to remove the air from the dome creating a very low pressure zone within the dome... as the pressure dropped, the water ...

0

If a cold beer can is taken out of the fridge on a warm day small water droplets form on its surface since the surface temperature is below the dew point of the moist ambient air. After a while, when the can reaches equilibrium temperature the water gets evaporated away again. For the ice cube the same is true in principle besides it evaporates away ...

3

Imagine spinning a roulette wheel, but instead of dropping in one ball, you drop in 100. They all rattle around at different speeds, like the molecules in water. You can cool them down by spinning the wheel slower, so they bounce about less; heat them up by spinning faster so they bounce more; you can freeze them by stopping the wheel and waiting till ...

0

These answers account for the kinetics of the process. Thermodynamics provides an alternate picture, well suited for any question involving phase transitions. For the system of liquid plus empty volume, the free energy can be lowered by trading some enthalpy (to take molecules from the liquid into the gas phase) for the increase in entropy (all the states ...

-1

The matter is constant. The mass increases (latent enthalpy of fusion plus specific heat as temperature rises) but ${m = E/c^2}$, hence way too small to measure. What is big enough to measure is the deceasing net buoyancy for displaced air by the denser mass (lesser volume) of of water versus ice, about 1.3 ${mg/cm^3}$ differential air volume at STP. If ...

1

The saucer ('cup') contains the ice at the beginning, which will melt so it contains water. As we are interested in what the scale shows us - the change in mass - it is not important whether it's ice or not, the mass would not change. The change we could observe is from evaporating water. How quick the water evaporates depends on the surface area, the ...

1

The mass of the melted water will be slightly lower than the ice. This is because the Latent Heat of Evaporation is higher than the Latent Heat of Fusion, so more water will be evaporated as it is turns into the liquid form and hence more mass will be lost. So gradually, as the water melts, the rate at which the mass is lost increases and hence the graph ...

6

Temperature is a measure for how much kinetic energy the molecules in a substance have. If the temperature is high, they are moving pretty fast, if the temperature is low, they are moving a lot slower. If molecules are moving slow, they bundle up and you get a solid. Once you heat it up a bit, the substance starts to become liquid. When you heat it up even ...

4

The way your question is phrased, it looks like you are expecting the mass to change. In that case the only change will be a slight mass loss due to evaporation, but the rate of evaporation is a variable - dependant on room temperature, air pressure humidity and how still the air is above the sample.

0

It can also be understud by the idea of partial pressure. Water will evaporate in an atmosphere until its partial pressure has reached the vapour pressure given for the ambient temperarture (relative humidity of 100%).

1

At the boiling point the gas is produced inside the liquid, but at the surface you constantly have molecules going in and out. If the environment is kept quite dry, then few molecules will come back in with respect to the ones that leave. Off course the higher the temperature, the easier will be for a molecule to get enough energy to break free, but this can ...

37

Think of temperature as average kinetic energy of the water molecules. While the average molecule doesn't have enough energy to break the inter-molecular bonds, a non-average molecule does. Water is a liquid because the dipole attraction between polar water molecules makes them stick together. At standard atmospheric pressure (acting somewhat like a vice), ...

0

If a monolayer of water molecules is adsorbed on the surface of pore, the van der Waales potential acting on a molecule is increased due to negative curvature of the water surface (eg. concave meniscus) and capillary condensation sets in already below the saturation pressure of water. It shifts the sorption isotherm of the porous material towards higher ...

4

While the capillary pressure in soil is many orders of magnitude lower than the atmospheric pressure, you also need to remember that in soil, the water is still in contact with the atmosphere, and thus is at atmospheric pressure plus capillary pressure. Since atmospheric pressure is orders of magnitude larger than capillary pressure, the pressure on the ...

19

It's not poop. It's fly barf. A fly spends about 25% of its time re-digesting and it only can eat liquids. It mixes the eaten food with the appropriate enzyme for digestion. The fly does this by retrieving the eaten food from its digestive system (a vomit of sorts), and drop by drop it is placed on the surface on which the fly is sitting. Only then is it ...

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