化学兴趣小组对CO2与NaOH溶液反应的发生进行了探究。
（1）从压强变化的角度探究。
①利用图甲装置进行实验，先挤压胶头滴管，再打开止水夹，观察到烧瓶内形成红色“喷泉”，原因是烧瓶内压强 （填“大于”或“小于”）外界大气压；
②利用图乙装置进行实验，分别将等体积的NaOH溶液和水同时注入盛有等体积CO2的玻璃容器中。证明CO2与NaOH溶液发生反应的实验现象是 ；
③写出CO2与NaOH溶液反应的化学方程式：。
（2）利用“数字化实验”探究。
①写出图丙中制取CO2的化学方程式：，检验CO2的方法是 ；
②实验测得烧杯中溶液的pH随时间的变化关系如图丁所示，可推知反应过程中浓度不断减小的离子是 （填离子符号）。
（3）氯碱工业生产的烧碱样品中常含有Na2CO3和NaCl等杂质。为测定烧碱样品中Na2CO3的质量分数，称取20g烧碱样品，加足量水溶解，再加入足量的BaCl2溶液，充分反应后，过滤，将滤渣洗涤、干燥、称量，得到0.197g碳酸钡（BaCO3）固体。
①检验烧碱样品中是否含有Na2CO3，可选择的试剂是 （填字母）；
a．稀盐酸
b．澄清石灰水
c．酚酞
②计算烧碱样品中Na2CO3的质量分数（写出计算过程）。
Dogs are the best pets of humans. They come in all sizes. Some dogs are as small as a football, and others are as tall as a desk. Dogs’ fur (毛) is different, too. It can be long and soft, or smooth and hard. People don’t mind the kind of fur, because all dogs are good to hug.
请在字典中查一下这个词。
我喜欢甜食， 你知道的。
去年， 彼得在旅途中和许多人交了朋友。
我叫托尼· 史密斯， 史密斯是我的姓。
我们在课上回答问题时应该起立
Tea and coffee are two of the most popular drinks in the world. However, people usually like one more than the other. These drinks also have very different uses.
People in the office usually sit for most of the day when they work. But this is bad for a person’s health. When people sit for too long every day, they don’t move very much. So it is easy to start getting fat. Sitting too long is also bad for their work because it makes them want to sleep. When this happens, people may make more mistakes in their work or spend more time finishing their work. Companies need workers to be healthy, so how do they fix the problem?
