Density of Ice

In the hydrogen-bonded lattice of ice, the individual water molecules cannot pack together as tightly as they would if there was no hydrogen bonding. Consequently, the density of ice is lower than that of water. Ice cubes float benzene cubes sink. 

The density of ice is less than that of water so that ice floats. Having a frozen ice cap protects life below the ice, whereas a solid phase that sinks means that solid forming near the cold surface will sink, leaving new liquid to freeze and eventually freezing throughout any body of liquid. 

With the suggestion that the last common genetic ancestor is a hyperthermophile, the role of temperature on the origins of life is important. The lower temperature limit in water is limited by the phase transition from liquid to ice. This is a problem because the density of ice is lower than that of water and the increase in volume on freezing will cause the cell structure to become disrupted in the same way that pipes burst in the winter. The lower limit for bacterial growth reported so far is -20°C, which is the temperature at which intracellular ice is formed. Adaptation to the cold requires a considerable salt content to depress the melting point of water the Don Juan Pond in Antarctica, which has a saturated CaCE solution, preserves the liquid phase at temperatures as low as —53°C. 

The somewhat open network structure of solid water determines that the density of ice at 0 °C is 916.7 kg m 3. That of liquid water at 0 °C is 999.8 kg m 3 so solid ice floats on water, a fact noticed eventually by the captain of the Titanic1. In liquid water at 0 CC there is still considerable... 

From tha preceding remarks, the cause of ice— solidified or crystallized water—floating in water will be readily understood. It has been shown that at the point of solidification the liquid has the same, if not a lesser density than at 40° but, in passing to the Solid state, the gravity is much further reduced, as well by the arrangement which its particles assume, as by the expulsion of the gases dissolved in the water, and which, before they can escape, are enveloped and compressed within the solid crystal. From both, and perhaps other conjoint causes, the density of ice at a temperature of 32° is less than that of water at 212°, and hence the former floats in the latter. At the normal degree at which chemists are accustomed to compare the densities of bodies, namely 60s, and a barometric pressure of the atmosphere of thirty inches, pure water is taken as the standard of comparison, and is expressed by unity, or 1000—compared to this ice has a density of 0-916. 

When water freezes, it expands. What does this say about the density of ice compared with the density of water ... 

In ice, the water molecules form well-defined structures with some empty spaces or channels in them. That is why the density of ice is less than that of liquid water. In the liquid, there is little empty space. 

Lower density of ice Lakes do not freeze completely in winter. 

An Earth example not previously discussed deals with the roles of temperature and pressure on the density of ice cores (Marion and Jakubowski 2004). Gow (1971) has shown that the density of deep ice cores under pressure relaxes elastically as soon as the cores are extracted. In Fig. 5.9, we used our model parameters to calculate how the density of an ice core from Antarctica (Gow et al. 1968 Gow 1971) would vary with core temperature at 1 atm, which is what is measured at the surface with corrections for temperature, to the same core under both temperature and pressure constraints. At 1 atm pressure, the core density changes linearly with temperature (Fig. 5.9), in agreement with our model (Fig. 3.2) and the Gow (1971) results (see his table 1). In contrast, the density of the ice core subjected to both temperature... 

Although the density of ice at the experimental temperature is not stated, it could not be very different from the value at 0°C, which is 0.92 g/cm3. 

The specific gravity at 0° C. differs from the true density of ice at 0° C. by an exceedingly small amount, since 1 gram of water at 0° C. has a volume of T000132 e.c., and thus differs from 1 e.c. by only 0 013 per cent. 

It will be noticed that Bunsen s value for the density of ice I differs only by about 0-1 per cent, from that of Leduc, and the latter author suggests that the difference is mainly due to the fact that Bunsen had not removed every trace of air from his water. Compared with all the results, however, Leduc s value appears somewhat high, and Roth,1 in a critical survey, recommends the mean value 0-9168 as probably most nearly correct. 

Value depends on that assumed for contraction of ice on melting. Bunsen used 0-91674 as density of ice. Bunsen, Pogg. Annalen, 1870, 141, 1. 

A sphere of ice with a 10 cm radius is initially at 273.15 K. This ice sphere is placed on a sponge, which absorbs the melted water. Determine the diameter of the ice sphere as a function of time. Assume that the heat transfer coefficient is 5 W/(m2 K). The latent heat of melting is 333 kJ/kg, and the density of ice is approximately 0.917 kg/m3. 

How much time is required to form a layer of frost 0.1 mm thick on each side of a leaf under the previous conditions (Although thin, such a layer of frost is readily visible.) Because / ost equals Jw, Hsub (see Eq. 7.22), the rate of water deposition per unit area (7W) in kg m-2 s 1 is 7 ost in J s-1 m-2 divided by Hsub in J kg-1 (Hsub is 2.83 x 106 J kg-1 at -1°C Appendix I). This Jw (mass of water per unit area and per unit time, kg m-2 s-1) divided by the mass of ice per unit volume, which is the density of ice (p, 917 kg m-3), gives the thickness of frost accumulation per unit time in m s-1 (i.e., Jwvlpice = thickness/time). To accumulate 0.1 mm of ice on each side of a leaf therefore requires... 

Hydrogen bonding is responsible for the low density of ice compared with liquid water (Figure 13.12). This difference is absolutely necessary for hfe as we know it. Because ice is less dense than water, it floats on top of water and acts as a blanket to protect... 

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