7. How much heat will be required to raise the temperature of 8 lbs. of water 32°F.; 5 lbs. 10°F.? [Illustration: FIG. 125.--A clinical thermometer used to take the temperature of the body.] 8. How much heat will be required to raise the temperature of 30 g. of water 43°C.; 20 g., 50°C.? 9. Compute the temperature of absolute zero on the Fahrenheit scale. 10. Take three basins of water, one hot, one cold, and one lukewarm. If one hand be placed in the hot water while the other is placed in the cold and after a few minutes both are placed in the lukewarm water, this water will feel cool to one hand and warm to the other. Explain. 11. If 200 ccm. of air at 200° absolute is heated to 300°A. under constant pressure, what volume will the air occupy at the latter temperature? 12. How does one change a reading on the centigrade scale to a corresponding reading on the absolute scale? (3) EXPANSION OF LIQUIDS AND SOLIDS =146. Expansion of Gases.=--The law of Charles is found to apply to all gases. That is, all gases change in volume in proportion to the change of temperature provided the pressure remains constant. It is for this reason that we have the _gas thermometer_ (see Fig. 126) which gives in skillful hands more accurate temperature readings than the best mercurial thermometer. Galileo devised and used the first _air thermometer_ which consisted of a hollow bulb blown on a glass tube and inverted in a dish of water. (See Fig. 1.) The _water thermometer_ consists of a glass bulb filled with water which rises into a tube attached to the bulb. One disadvantage of the water thermometer is its limited range since it cannot be used below 0° or above 100°. Why? =147. Expansion of Liquids.=--The expansion of liquids differs from that of gases in several important respects: (a) Liquids have a smaller rate of expansion than gases. The _rate_ of expansion per degree is called the _Coefficient of Expansion_. For example, the coefficient of expansion of a gas under constant pressure at 0°C. is {1/273} of its volume per degree centigrade. (b) Different liquids expand at wholly different rates, that is, their coefficients of expansion differ widely. For example, the coefficient of expansion of mercury is 0.00018 per degree centigrade, of glycerine 0.0005 per degree centigrade, of petroleum 0.0009 per degree centigrade. [Illustration: FIG. 126.--Gas thermometer.] (c) The same liquid often has different coefficients of expansion at different temperatures. Water between 5°C. and 6°C. has a coefficient expansion of 0.00002 per degree centigrade, between 8° and 50° of 0.0006, between 99° and 100° of 0.00076. The coefficient of expansion of mercury, however, is constant for a wide range of temperature and, therefore, it is well adapted for use in thermometers. =148. Peculiarity in the Expansion of Water.=--Water has a peculiar rate of expansion. This is illustrated by the following experiment: