Water Is Densest at

Hewitt, Conceptual Physics, 10th ed. San Francisco Addison-Wesley 2006. www.conceptualphysics.com 

Within a few degrees of 0°C, liquid water contains crystals of ice. The open structure of these crystals makes the volume of the water slightly greater than it would be without the crystals. 

Between 0°C and 4°C, the volume of liquid water decreases as the temperature increases. Above 4°C, water behaves the way all other substances do its volume increases as its temperature increases. The volumes shown here are for a 1-gram sample. 

0 Liquid water below 4°C is bloated with ice crystals. 

As water cools to 4°C, it sinks. Then, as water at the surface is cooled to below 4°C, it floats on top and can freeze. Only after surface ice forms can temperatures lower than 4°C extend down into the pond. This does not happen very readily, however, because surface ice insulates the liquid water from the cold air. 

Upon warming, the crystals collapse, resulting in a smaller volume for the liquid water. 

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The atmospheric circulation is driven by temperature differences over the globe. The atmosphere is a fluid heated from below, and fluids that expand when heated, like air, rise when heated from below. The world s oceans differ from the atmosphere in two important respects (1) the oceans are heated from above and (2) water is densest at 4°C. It expands both when cooled below 4°C and heated above 4°C. 

The ash is mixed with 5 to 10 per cent, of slaked lime and placed in wooden barrels with false bottoms. Hot water is poured over the mixture, and, after standing for some time, the liquid is drawn off from time to time by removing a plug near the bottom of the cask. The liquid with a sp. gr. over 1 -15 is evaporated the low sp. gr. liquor may be used for lixiviating more ash and the residue in the barrels may be used as manure. The evaporation of the densest liquor to dryness is conducted in cast-iron pots, and the residue is afterwards calcined in a reverberatory furnace to burn away the organic matter—at the same time sulphates may be converted into sulphides. The product is crude potash. The crude potash may be mixed with sawdust and re-calcined. It is then digested with twice its weight of hot water, filtered, and cooled. The less soluble impurities—mainly potassium sulphate—crystallize out, and finally the mother liquid is evaporated to dryness and calcined as before, - or the solu. may be evaporated until crystals of potassium carbonate are deposited. 

Page 74. Water is in its densest state at a temperature of 39.10 Fahrenheit. 

As Water is of a nature closely approaching that of the First Matter of the World, it becomes easily its symbol, or image. The chaos, whence all was derived, was like a vapor, or a humid substance, similar to a subtle smoke. Light having rarefied it, the heavens were formed of the most subtilized portion the Air of that which was less so the elementary Water of that which was a little more terrestrial and the Earth, of the densest, and as feces, (Raymond Lully, Testam, Anc. Theor.). Therefore Water partaking of the nature of the Air and Earth, is placed in the middle. Lighter than the Earth and heavier than Air, it is always mixed with both. At the least rarefaction it seems to abandon the Earth to take the nature of the Air it is condensed by the least cold, it quits the Air, and unites itself with the Earth. 

Venus has the densest atmosphere of all the terrestrial planets. The principal atmospheric constituents are carbon dioxide and nitrogen (N2) their mixing ratios are approximately 96.5% and 3.5%, respectively, below, 100-km altitude. Trace constituents below 100-km altitude are in the range of 0.1%. The Venus atmosphere is covered with thick clouds composed primarily of sulfuric acid and contaminants, making the surface invisible from above. The total pressure at the bottom of the cloud layer ( 47 km) is approximately 1.3 atm. Water is highly depleted throughout the atmosphere. The mean physical structure of the atmosphere (pressure and temperature profile) is reasonably well known from the data returned by a number of space probes. The surface pressure and temperature (on a mean surface) are approximately 94 atm and 737 K, respectively. 

Iridium metal is silvery-white with a density of 22.65 grams per cubic centimeter. A cubic centimeter of iridium weighs 22.65 times as much as a cubic centimeter of water. It is one of the two densest elements known (the other being osmium). Iridium has a melting point of 4,429°F (2,443°C) and a boiling point of about 8,130°F (4,500°C). Cold iridium metal cannot be worked easily. It tends to break rather than bend. It becomes more ductile (flexible) when hot. Ductile means capable of being drawn into thin wires. Therefore, it is usually shaped at high temperamres. 

Density. Atomic size, and therefore volume, is inversely related to density. Across a period, densities increase, then level off, and finally dip a bit at the end of a series (Figure 22.4D). Down a transition group, densities increase dramatically because atomic volumes change little from Period 5 to 6, but atomic masses increase significantly. As a result, the Period 6 series contains some of the densest elements tungsten, rhenium, osmium, iridium, platinum, and gold have densities about 20 times that of water and twice that of lead. 

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