Boiling and disjunctive laws

In Uncategorized on February 15, 2010 by Joshua Smart

This is a minor point, but I note that Sober is wrong in his description of the law concerning boiling water. The law in this case is that water boils at 100C. Having the ambient temperature be over 100C is one way to raise the temperature of the water to 100C, but the relevant fact is that the water itself reaches the boiling point. Also, the temperature of the water will not exceed 100C until it has completely transitioned to gas phase.

Can anyone think of a law that actually has the sort of disjunction Sober is looking for?


3 Responses to “Boiling and disjunctive laws”

  1. Water boils at lower temperature than 100C if it is at a very high altitude, in very great pressure, etc.. If we take altitude and pressure into consideration, we can formalize a law that uses disjunction.

    Since the density of water and the density of the sea are different, we can also formalize a disjunctive law about what conditions an object will sink in water or in the sea.

  2. When water freezes, it expands and thus its density decreases, but at even lower temperatures its density begins to increase again, slightly. Though explainable completely by chemistry, the ‘law’ about the observable phenomena is disjunctive in the sense that Sober was seeking. More technically, from the wikipedia entry on ‘ice’:

    An unusual property of ice frozen at atmospheric pressure is that the solid is approximately 9% less dense than liquid water. Ice is the only known non-metallic substance to expand when it freezes. The density of ice is 0.9167 g/cm³ at 0°C, whereas water has a density of 0.9998 g/cm³ at the same temperature. Liquid water is densest, essentially 1.00 g/cm³, at 4°C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C (93 K).

  3. Josh: Fahrenheit 451.

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