Page 32 - Curriculum Visions Dynamic Book

Viscosity
The runniness of a liquid is called its viscosity. You may think that water is a very runny substance, but it is much less runny than some other liquids, for example, gasoline.
In many liquids the warmer the liquid, the runnier it becomes. This shows very dramatically with oil, for example, where cooking oil is far more runny when heated than when poured cold straight from a bottle. However, the difference is not very obvious with water. This is yet another unusual property of water. It means that we can use cold water in much the same way as hot water without having to worry about its viscosity. That would not be true for oil.
Water, however, behaves differently when other substances are added to it, creating a mixture called a solution. In general, additives make the solution “thicker” and as a consequence “stickier,” and the viscosity changes with temperature.
Heat conduction and storage
Water is very good at holding heat. Water is said to have a very high heat capacity, or thermal capacity. Water can also conduct heat quite well, certainly
very much better than air. That is why, for example, an ocean changes temperature very slowly through the seasons: It takes a long time for the warm, sunlit surface waters to conduct some heat downwards. But because water can store heat, the oceans are also slow to cool down in winter, thus keeping many coastal regions warmer than they otherwise would be.
One of the most common domestic uses of the heat capacity of water is in central heating systems. Water is heated in a boiler and then pumped to radiators in various rooms. By using water, a considerable amount of heat can be stored per unit volume, and this keeps down the amount of liquid that has to be pumped around the system.
In some energy-efficient houses there is a large tank of water beneath the basement. During the hot,
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Water draining out of sinks and toilets is well above the drains, and so it flows out under gravity.