Polar molecules have a weak charge, partially negative and partially positive. For example, in water, the negative charge is the oxygen atom and the positive charge is the hydrogen atoms in the water. When water molecules are close to each other, the positively and negatively charged regions are attracted to the oppositely charged regions or to nearby molecules. The dotted lines shown in the picture are called hydrogen bonds. Each water molecule is bonded to four other molecules. The hydrogen bonds created between water molecules are among the essential and unique properties of water. The attraction that occurs between hydrogen bonds keeps water liquid over a greater range of temperatures than for any other molecule. Additionally, a large amount of energy is required to transform liquid water into water vapor. When water is liquid, the molecules are attracted by their hydrogen bonds, which is not the case in water vapor. The results of these "essentials" are: When mammals cool themselves by the evaporation of their sweat, they achieve this thanks to the large amount of heat used to release themselves....