![]() The Water Encyclopedia, Third Edition, Hydrologic Data and Internet Resources, Edited by Pedro Fierro, Jr.Īnd Evan K. Department of the Interior, Bureau of Reclaimation, 1977, Ground Water Manual, from So, when they demanded another gallon of water, I consulted the "Internet" of that day-an encyclopedia- and found out that a gallon of water at the boiling point only weighed 7.996 pounds! I ran up the hill carrying my gallon of water that weighed 0.333 pounds less and ran back down even faster, their angry voices fading behind me. That gallon of tap water at 70☏ weighed 8.329 pounds, which was a lot for a 70-pound kid to haul up a huge hill. They got thirsty and made me go back home and bring them a gallon of water. One hot summer day they climbed the huge hill next to our house to dig a hole to hide their bottle-cap collection. I was able to use water density once to at least play a trick on them, though. Growing up with an older brother was difficult, especially when he had his friends over, for their favorite activity was thinking of ways to antagonize me. The rounded value of 1 g/ml is what you'll most often see, though. A common unit of measurement for water's density is gram per milliliter (1 g/ml) or 1 gram per cubic centimeter (1 g/cm 3).Īctually, the exact density of water is not really 1 g/ml, but rather a bit less (very, very little less), at 0.9998395 g/ml at 4.0° Celsius (39.2° Fahrenheit). Density is just the weight for a chosen amount (volume) of the material. As long as an object is made up of molecules, and thus has size or mass, it has a density. The definition of density, makes a lot more sense with a little bit of explanation. If you're not still in school, then you probably forgot you ever even heard it. On Earth, you can assume mass is the same as weight, if that makes it easier. The present results demonstrate the potential of metalloid-doped SMoSe JLs as efficient HER catalysts.If you're still in school, you've probably heard this statement in your science class: " Density is the mass per unit volume of a substance". In particular, adsorption and desorption of H on B-doped (at S and Se sites) and on Ge-doped (at an Mo site) JLs may be rapid. The most favorable sites are B at S and Se, Si at Mo and S, and Ge at Mo and S. The data show that all dopants may improve SMoSe for HER applications. In order to quantify the feasibility of the doped SMoSe JLs for use as a catalyst for the HER, the free adsorption energy is determined. While pristine SMoSe JLs repel H, several attractive sites are found in the vicinity of the dopant atoms. Consequently, the interaction of H atoms with these sites is studied and the H adsorption energy is calculated. Atomic sites with a number of electrons different from that on atoms in pristine SMoSe JLs may be potential hydrogen traps and are therefore interesting for the hydrogen evolution reaction (HER). The electron redistribution in the JLs due to the presence of dopants is explored using Bader analysis. Doping at the S site is energetically most favored, with E B f < E Si f < E Ge f. It is found that under X-poor conditions, the stability of the dopants is always higher. The formation energy E f of dopant X (X = B, Si, and Ge) at substitutional and interstitial sites is studied for two different chemical environments: (i) bulk X – or X-rich conditions, and (ii) dimer X 2 – or X-poor conditions. The detailed structural analysis exposes the influence of dopant atomic sizes on lattice distortion. Spin-polarized density functional theory calculations are employed to investigate the modified structural and electronic properties of the layers, the energetics of dopant incorporation, and the effect of doping on the interaction of the two-dimensional material with hydrogen. B, Si, and Ge dopants are inserted into SMoSe Janus layers (JLs) at Mo, S, and Se as well as at interstitial sites.
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