读写复印资料答案Unit2.doc

复印材料答案 第三单元课文翻译 Core Reading 1 What if I Ate the Silica Packets Marked “Do Not Eat”? Katherine Neer What you would be consuming is most likely silica gel or some other desiccant -- something that absorbs (collects) and holds water vapor. These little packets are found in all sorts of products to help maintain quality. Shipping can cause all kinds of atmospheric conditions and changes in temperature. Increased moisture can spoil or permanently damage many products. For example, if a bottle of vitamins contained any moisture vapor and was cooled rapidly, the condensing moisture would ruin the pills. You’ll find little silica gel packets in anything that would be affected by excess moisture or condensation. Silica gel can adsorb about 40 percent of its weight in moisture and can take the relative humidity in a closed container down to about 40 percent. Once the gel is saturated, you can get rid of the moisture and reuse silica gel by heating it above 300 degrees Fahrenheit (150 degrees Celsius). Silica gel is nearly harmless, and that’s why you find it in food products. Silica, which is actually silicon dioxide (SiO2), is the same material found in quartz. The gel form contains millions of tiny pores that can adsorb and hold moisture -- it’s essentially porous sand. While the contents of a silica gel packet are basically harmless, it would be a rather unpleasant experience to attempt to consume the silica crystals. The sole job of these tiny desiccants is to adsorb moisture. If you emptied a packet of the stuff into your mouth, the moisture would be whisked away from the sides and roof of your mouth, your gums and tongue -- giving an entirely new and all-too-accurate meaning of the phrase “dry mouth.” If silica gel did happen to make it past your mouth -- which is unlikely because you would probably be making every effort to spit it out -- you might suffer a few irritating side effects, such as: ?Dry eyes ?An irritated, dry feeling in your throat ?Aggravated, dry mu