某同学欲探究一包Ca（OH）2的白色粉末是否完全变质．
（1）猜想与假设：该包Ca（OH）2白色粉末未完全变质．
（2）收集证据：Ca（OH）2在空气中会与空气中的二氧化碳发生反应，反应的化学方程式为：______；
（3）实验探究：
| 实验步骤 | 实验现象 | 实验结论 |
| 样品中有氢氧化钙存在 | ||
由于氢氧化钙能够和空气中的二氧化碳发生反应生成碳酸钙而导致变质，若完全变质则只有碳酸钙，若没有变质则只有氢氧化钙，若部分变质则有碳酸钙和氢氧化钙，由于氢氧化钙是碱而碳酸钙是碳酸盐，氢氧化钙溶液能使酚酞试液变红，而碳酸钙能和稀盐酸反应有气泡生成．
故答案是：（2）CO2+Ca（OH）2═CaCO3↓+H2O（2分）
（3）
| ①取少量样品于试管中，加水，振荡，滴入酚酞试液（2分） | 溶液变红色 （2分） | |
| ②再向试管中滴入足量的盐酸溶液，（或另取少量样品，置于烧杯（或烧杯）中，滴加足量盐酸溶液）（1分） | 沉淀溶解，有气泡产生（2分） | 样品存在碳酸钙 （1分） |
Smiling People smile at times. However, the meaning of a smile in different cultures may be different. Depending on different cultures, smiling can express joy and amusement, but it can also indicate embarrassment（苦恼）. The following examples show this point of view: In an attempt to be open and friendly, people in the United States smile a lot. Every one smiles at each other, this nonverbal communication shows being friendly in the United States. However，in China, smiling is not only an expression of happiness, but also a way to avoid being embarrassed. Chinese people like smiling when they are embarrassed in order to avoid embarrassment. Smiling is a kind of good will but not sneer（嘲笑）. For example: When a child falls off from a bike, the adults in China may smile, which is a kind of gentle encouragement and may not be a kind of impolite laugh. When a person from the United States might blush（脸红）with embarrassment or become offensive, a Chinese might blush with smile. To avoid serious misunderstanding, people who engage in intercultural communication should be able to understand the meaning of smiling appropriately. Related to the smile is the laugh. Also, different cultures have different meanings about laugh. For example, Americans can enjoy a very heartfelt belly (腹部) laugh that comes from the deepest emotions. However, most Chinese seldom laugh that way because they are thought to be silly except among close friends. 小题1:We can use smile to express all of the following feelings except_________,
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