探究一:铁丝燃烧
如图1所示,取3根粗细、长度均相同的光亮细铁丝,将其中两根分别盘成螺旋状,在每根铁丝一端系上粗铜丝,另一端系一根火柴杆,点燃火柴杆待快燃尽时,分别插入充满氧气的集气瓶中,观察到:观察到:Ⅰ、Ⅱ中铁丝都剧烈燃烧,且Ⅱ中铁丝燃烧比I中的更剧烈;Ⅲ中铁丝没有燃烧.

如图2所示,将包有样品的滤纸包用大头针固定在橡胶塞上,迅速塞紧,观察到量筒内水沿着细导管慢慢进广口瓶(容积为146mL).当温度恢复至室温,且量筒内水面高度不变时读数(此时瓶内氧气含量近似为零).记录起始和最终量筒的读数以及所需时间如下表.

序号 | 样品 | 量筒起始 读数/mL | 量筒最终 读数/mL | 所需时间 /min |
1 | 1g铁粉、0.2g碳和10滴水 | 100 | 72 | 约120 |
2 | 1g铁粉、0.2g碳、10滴水和少量NaCl | 100 | 72 | 约70 |
3 | \ | \ | \ |
金属腐蚀的过程实际上就是金属元素化合价(填“升高”或“降低”)的过程.

D . 空气中的稀有气体含量少,不能直接从空气中分离获得稀有气体
A.连接好实验电路,把变阻器的滑动片调到最左端,电阻箱阻值调为0;
B.闭合电键,调节变阻器的滑动片,使电流表指针满偏,记录电压表V的读数U;
C.逐渐增大电阻箱的阻值,同时(选填“向左”、“向右”)调节变阻器的滑动片,使电流表的指针保持,记录几组电阻箱的阻值R和电压表V的读数U。


Almost every child in cities has the chance to go to school, but not all children in the countries are so lucky.
There is a girl called Xiao Fang. She is eight years old and lives in a small village in Guangxi. When she was young, she wanted to go to school. But she could not, because her family was too poor to afford the school fees for her, so her parents had to keep her at home. Instead of studying, Xiao Fang worked in the fields with her parents every day. Then Project Hope heard about Xiao Fang. It agreed to help Xiao Fang to go to school. Her wish of study came true, and now she is studying in a school.
Unluckily there are many thousands of children who can not go to school. You can join in Project Hope and help these children. You know all the good work needs money. Project Hope needs your help.
If you give Project Hope¥300 each year, it can pay for one child to go to school for a whole year. With more money, Project Hope can build new schools, buy good desks, chairs, blackboards and books. Let's help the children together and give them a chance to have a good start in life.