在家庭中自制汽水时需要在饮料中加入白糖、果汁、小苏打（NaHCO3）、凉开水，还需加入柠檬酸。
（1）加入柠檬酸的目的是 ；
（2）饮用时，将瓶盖打开，会有大量气泡冒出，原因是 ；
（3）饮用汽水后，往往易打嗝，原因是 。
（1）柠檬酸和小苏打反应产生二氧化碳气体
（2）打开瓶盖，压强减小，气体溶解度减小，CO2气体从液体中逸出
（3）人的胃中温度较高，气体的溶解度减小，从胃中逸出
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| Young people and 1 people do not always agree. They sometimes have 2 ideas about living, 3 and playing. But in one special program in New York State, adults and teenagers live together in 4 . Each summer 200 teenagers and 50 5 live together for eight weeks as 6 of a special work group. Everyone works several hours each day. The aim is not just to keep busy. It is to find meaning and 7 in work. Some teenagers work in the woods or on the 8 near the village. Some learn to make furniture and to build houses. The adults 9 them these 10 . There are several 11 hours each day. Weekends are free, too. During the free hours some of the teenagers learn photography or painting 12 sit around and talk or sing. Each teenager chooses his own way to 13 his free time. When people live together, 14 are always necessary. In this program the teenagers and the adults make the rules together. 15 someone 16 a rule, the problem goes before the whole group. The group discusses the 17 . They ask, "Why did it happen?" 18 should we do about it? One of the teenagers has this to say about the 19 : "You stop thinking only about 20 . You learn how to think about the group." | ||||
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