4.电极判断：
①由组成原电池的两极电极材料判断。一般活泼的金属为_________极，活泼性较弱的金属或者能导电的非金属为__________极。
②根据电流的方向或电子流动的方向判断。电流由________极流向_____极；电子流动的方向是由______极流向______极。
③原电池输出电能的能力，取决于
3.正、负极判断(以Zn│H2SO4│Cu)原电池为例
负极：______________(_____反应) 正极：________________(_____反应)
总反应： 。
[实验装置]书选修4：P12
[思考]：观察导线中电子流向和溶液中离子迁移，盐桥中有哪些物质?盐桥起什么作用？
2.构成原电池的条件
1.定义：_______________________________________________。
39.(2010·合肥模拟)Some parts of the city due to less-developed economy is _______ populated.
A. few B. little C. seldom D. hardly
[答案]1-5 BCBBD 6-10 DDBBA 11-15CBBDB 16-20CADCA
21-25 DBBCA 26-30DBDBC 31-35 CBDCB 36-39DDAD
38. (2010·长沙模拟) She not only entered the competition-she _______ won it!
A. actually B. especially C. hopefully D. exactly
37.(2010·双鸭山模拟)We noticed an old man lying on the ground, _________.
A. coldly and hungrily B. coldly and hungry
C. cold and hungrily D. cold and hungry
36.(2010·泰安模拟)She felt even more ____ when she was waiting ____ among strangers.
A. lonely; lonely B. alone; alone C. alone; lonely D. lonely; alone
35.(2010·长沙模拟) It is important to keep ______ in an emergency.
A. quiet B. calm C. silent D. still
34.(2010·扬州模拟)It was very ______ of you to send me a postcard when you were on holiday in Hong Kong.
A. considerable B. innocent C. considerate D. unconscious