The Different States of Water and Their Properties.

Solid water

As water solidifies, it can be amorphous or regularly crystallized. The crystalline form of solid water is that of a hexahedral prism with angles of 120°, or that of an isosceles dodecahedron. These crystals exhibit double refraction and belong to the rhombohedral system.

According to Scoresby and Dufrenoy, snow often takes the form of six-pointed stars, with each point being a regular six-sided prism; sometimes even the center of the star is occupied by a small, shiny hexagonal plate, and the points of the star extend from each of its corners.

When water changes from a liquid to a solid, its volume increases. Its density becomes 0.916 or 0.918 according to M. Brunner, with that of water at + 4 °C being 1.000.

This increase in volume as water solidifies explains:

1. Why ice consistently remains on the surface of still water,
2. Why water in the cellular tissue of plants or fruit, which solidifies during a hard frost, causes capillary vessels to rupture as its volume increases, kills plants in a short time, and causes frozen fruit to decompose rapidly,
3. Why fountains and carafes filled with water often break during the cold of winter when the water they contain solidifies: water pipes that are not buried deep in the ground also burst when the water flowing through them freezes,
4. Why stones described as frost-susceptible, which can accumulate a considerable amount of water, break in winter as a result of the expansion of the water in their pores as it freezes,
5. Why water, as it solidifies, sometimes causes even the strongest metals and alloys to rupture.

This is how gun barrels, and even bronze cannons, can be broken by filling them with water, sealing them tightly, and exposing them to a temperature that causes the water they contain to solidify.

As ice melts, it maintains a constant temperature that is used as the starting point for thermometers and defines zero on their scale. The point at which water freezes often varies considerably and is therefore not used to establish zero on thermometers. According to Gay-Lussac, when water is not agitated, its temperature can be lowered to -42° without it solidifying; if it is agitated, it freezes immediately, and a release of heat is observed that quickly raises its temperature back to zero.

The freezing of water therefore involves two remarkable phenomena: a release of heat and an increase in volume.

Water containing dissolved salts freezes more slowly than pure water. When a salt solution partially freezes, pure water solidifies first, while the salts remain in the mother liquor. This property has been used to concentrate certain salt waters.

As ice melts, it absorbs a considerable amount of heat. The amount of heat required for a given weight of ice at zero to change state is equal to that needed to raise the same weight of liquid water from 0 to 79°, as demonstrated by the experiments of Provostoye and Desains. Thus, when equal weights of snow at 0° and water at 79° are mixed, the mixture melts and its temperature remains at 0°.

Liquid water

Water is odorless, tasteless, and colorless, but in large quantities it has a greenish tint. When water initially at zero is heated, its volume decreases until + 4°, then increases steadily up to its boiling temperature.

At 8 °C, the volume of water is approximately the same as at 0°. According to Despretz, its maximum density occurs at 4°.

As a solvent, water is of interest to the arts, industry, and chemical analysis alike. A substance's degree of solubility or insolubility in water is therefore ranked among its foremost properties.

Water in its vapor state

The boiling point of a liquid is always the same under the same pressure. Water boils at a constant temperature, which is used to establish the hundredth degree on the thermometer scale.

At 100 °C, water expands to approximately 1,700 times its volume as it turns into vapor.

The boiling temperature of water varies with pressure. By enclosing water in a sufficiently strong vessel, it can be heated to a very high temperature while preventing it from boiling. This experiment is performed in an apparatus known as Papin's digester.

Cagniard-Matour enclosed water in very thick glass tubes, purged of air and flame-sealed. By heating these tubes until they began to glow red, he established that water can turn into vapor in a space only four times greater than its own volume.

Water vapor is odorless, colorless, and transparent; its density is 0.662.

Like all volatile substances, water gives off vapor even at the lowest temperatures. This evaporation increases with temperature.

When cooled, water vapor condenses and becomes liquid water. This condensation occurs in atmospheric air when it contains more vapor than it can hold at saturation. This is how dew, hoarfrost, fog, rain, or snow forms. Water vapor condensed in the atmosphere is called fog when it is at the Earth's surface and a cloud when it is suspended at a certain height in the atmosphere. As vapor condenses in the air, it forms small spheres that constitute vapor in vesicular form.

To transform completely into an elastic fluid, water requires approximately five and a half times as much heat as it does to warm from 0 to 100°. This principle has been used in factories to bring large quantities of water to a boil in wooden vessels, which would be damaged by direct exposure to fire. When steam condensing could be harmful, it is circulated through a double bottom or through pipes immersed in the liquid to be heated.

Chemical properties of water

Water has no effect on colored reagents. It cannot be decomposed by heat. Several elements decompose it: some, such as chlorine, combine with its hydrogen and allow its oxygen to escape; others, such as potassium, iron, etc.,take up its oxygen while allowing its hydrogen to escape.

Water combines with a large number of substances in definite proportions, forming compounds known as hydrates.

When it combines with acids, bases, and salts, water generally does not change their distinctive characteristics; the properties of these substances are therefore usually studied in their hydrate forms.

However, in some cases, water combining with acids, bases, or salts causes significant changes in their properties.

Most substances do not decompose when dissolving in water; however, a number of salts, such as bismuth nitrate, potassium stearate, etc., separate into two parts upon contact with water, one of which is insoluble and precipitates, while the other is soluble and remains dissolved in the water.

Chevreul particularly drew chemists' attention to this class of phenomena.