Biological importance of the anomalous expansion of water

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Biological importance of the anomalous expansion of water The peculiar expansion of water has an important bearing on the preservation of aquatic life during very cold weather (Fig. 15.15). As the temperature of a pond or lake falls, the water contracts, becomes denser and sinks. A circulation is thus set up until all the water reaches its maximum […]

Density changes in water

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Density changes in water The density changes which occur when a piece of ice at – 10°C is gradually heated up to 100°C are shown in Fig. 15.14. The maximum density region on this graph should be compared with the corresponding volume changes shown in Fig. “15.13. Note how much greater is the density change when ice melts […]

Frost heave

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Frost heave One problem brought about by the expansion of water on freezing has occurred in cold store buildings. This is frost heave, the name given to the damage caused to the buildings when the water in the subsoil beneath the site freezes and expands, causing upward bulging of the floor and damage to foundations and walls. […]

The unusual expansion of water

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The unusual expansion of water Some substances do not always expand when heated. Over certain temperature ranges they contract. Water is an outstanding example. If we start with some ice at -10 °C and supply it with heat, it expands just like 0any other solid until it reaches 0 DC. After this it begins to melt while […]

Real and apparent expansion of a liquid

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Real and apparent expansion of a liquid Unlike solids, liquids have no fixed length or surface area but always take up the shape of the containing vessel. Therefore, in the case of liquids we are concerned only with volume changes when they are heated. The real (or absolute) expansivity of a liquid is the fraction of its volume […]

To compare the expansions of various liquids

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To compare the expansions of various liquids Different liquids have different thermal expansions. To demonstrate this, several fairly large glass bulbs with glass stems are filled to a short distance above the bulb with various liquids (Fig. 15.12). In order to make a fair comparison, the bulbs and stems must all be of the same size. The bulbs […]

EXPANSION OF LIQUIDS

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EXPANSION OF LIQUIDS We have already seen that liquids expand, in connection with our study of liquid-in glass thermometers. The expansion of a liquid may be shown by means of a flask fitted with a rubber bung and a length of glass tubing (Fig. 15.11). The flask is filled with water or other liquid and the bung pushed […]

Expansion in area and volume

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Expansion in area and volume Corresponding with the equation above, we have similar equations to give the new area and volume when thermal expansion takes place. where Al and A 2′ and VI and V 2 represent the areas and volumes before and after a temperature rise of (J and f and y the coefficients of superficial […]

The gas thermostat

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The gas thermostat Oven temperature control in a gas-cooker is effected by utilizing the exceedingly low thermal expansion of invar, an alloy of steel with 36 per cent of nickel. From the table on page 163 it will be seen that invar expands by only one-millionth of its length per kelvin rise in temperature. The flow of gas […]