Introduction to Chemistry

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. PHYSICAL TRANSFORMATIONS. 6. Fusion And Solidification. 29. Fusion. ? A solid substance does not remain a solid under all conditions, but on being heated it can be transformed to a liquid. This fact is apparent every winter. If the temperature is below 0 C., solid ice and snow lie on the streets, fields, and brooks. As soon as the temperature has risen above the freezing point, the solid ice is transformed again into liquid water.1 Then the streets which were dry become wet and the rigid covering on the river is set in motion. All other solids behave like ice in this respect, except that the temperature at which the melting or fusion takes place varies greatly. Wax melts in hot water, sulphur must be heated a little hotter, lead melts readily in a flame, but copper and iron do not, although even these metals can be liquefied by still more heat. Carbon will not melt in any furnace, but only in the electric arc. Every substance, however, can be liquefied eventually, for it is possible to reach the required temperature. Conversely, it is possible by cooling to transform every liquid into a solid. Liquid iron solidifies at about 1400 C., water at 0, and alcohol at ?112.3 C. Whether a substance is solid or liquid under ordinary conditions depends upon the location of the melting or solidification point. If it lies above about 15 C., we know it as a solid; if below, as a liquid. If we were living at a temperature of about 500, our world would have a quite different appearance inasmuch as many substances which we now know as solids would then be kept in vessels as liquids. 1 The melting of the ice requires some time, but the temperature of the water in contact with the ice remains at the freezing point until all the ice is melted. 30. Forms of matter. ...