# Tag Info

1

I copied some data when I was trying to predict the drying time of a paint: "The evaporation of water does not depend on the depth of a lake. It depends on the temperature and the wind. At 10°C, the level of the water decreases by 0.9mm/day if the wind is zero, by 1.2mm/day with a 2m/s wind, and by 1.7mm/day with a 9 m/s wind. At 20° C, those values are ...

1

In English at least, there is no single word that captures this quality, for the simple reason that fire can affect materials in many different ways. For example, an organic material may actually catch on fire itself and be combusted. "Combustibility" and "flammability" refer to slightly different descriptions of the tendency of materials ...

2

A1: There is no displacement of the wall, forces are in equilibrium with zero net force. There are initiated stronger vibrations on warmer wall side by energetic hot air molecules. And weaker vibrations on colder wall side by energy leaching cold water molecules . A2a: If the wall initial temperature was the cold water temperature, then yes. Otherwise no, as ...

8

The $\pu{3.6-3.8 V}$ range is a good general choice, but it may be battery-specific. The particular voltage for 40% charge may differ for different cell technologies, e.g. various deviations of electrode materials and due to cell aging. The optimal storage conditions, as you mentioned, are more often expressed as charge/capacity % ratio. Usually, the optimal ...

7

It looks like a brass ( a class of alloys, containing mostly copper and zinc, being golden-like ), which surface was covered by protective plating , possibly by chrome or nickel(*). It was probably worn out mechanically and/or by corrosion due acidic sweat. (*)Nickel plating could be worn out easier than hard and resistant chrome.

2

I found this description of how the horn is prepared in a post by Tammy L. Austin, at the University of Notre Dame's website (https://www3.nd.edu/~rbarger/www7/hornbook.html): The horn of oxen and sheep were used to make the laminating structure. The horn was left in cold water for several weeks, which separated the usable part from the bone. It was then ...

1

So the intermolecular forces would be stronger in glycerol then in acetone. Glycerol can form hydrogen bonds while acetone is not very polar and can’t significantly form h bonds with itself. The surface tension for glycerol is 63.4 $\frac{mN}{m}$ while acetone is 25.2 $\frac{mN}{m}$ (both @ 20 C) I supposed the error in your experiment arises from using ...

0

I can't answer why they ultra pasteurize it with absolute certainty but my guess would be because there is less demand for lactose free milk so the extended shelf life will prevent waste if it doesn't sell quickly. Sugar, like salt, retards bacterial growth, it doesn't increase it. That's why candy and sugary baked goods aren't refrigerated. The 2 types of ...

1

It does not have to be a full-fledged alkali to generate this color change effect. Alkaline earths work quite well (and less hazardously) even with only limited or sparing solubility. For a neat-looking demonstration with magnesia (or more accurately, the hydroxide it produces in water), see the picture and do the experiment here.

4

Generally, many dyes, natural or artificial, change color with changing pH ( acidity ). Natural anthocyan dyes are usually about red in acidic, about blue/violet in alkaline solutions. You can e.g. check red beetroot juice when washing soda is added. So that clear solution was probably an alkaline solution. These reactions are reversible, if pH is returned ...

3

Water reacts with the magnesium sacrificial anode over time to make $\ce{H2}$. Normally, you'd be using your hot water often enough that you wouldn't notice the minute amounts of $\ce{H2}$ coming out the tap with the hot water. But if your place is vacant for some time, a significant amount of $\ce{H2}$ could build up and an ignitable mixture come out the ...

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