THE ELEMENTS OF CHEMISTRY CHAPTER I CHEMICAL, CHANGES-PHYSICAL CHANCES Some Familiar Changes.-You are all familiar with many changes which are taking place in the things around you. Take, for example, the changes which are called ftre. You see substances destroyed by fire. They disappear. You feel the heat produced by the burning. You know that some things will burn and others will not. Again, you all know that iron when exposed to the air is changed, becoming covered with a reddish-brown substance called rust. If fruit-juices or milk be allowed to stand in contact with the air they become sour. If a spark comes in contact with gunpowder there is a flash and the powder disappears, dense smoke appearing in its place. Changes of Another Kind,-If a piece of stone or of iron be brought in contact with something hot it becomes hot itself. If taken away it becomes cool again. If heated very hot it gives light. When, for example, iron becomes " red-hot " we can see it in a dark room.Table of...

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