（2015•酒泉）2015年4月6日，漳州PX项目发生爆炸并引起大火，PX项目又一次引起人们的热议．PX是1，4﹣二甲苯（化学式为C₈H₁₀）的别称．请计算：

水和溶液在生命活动和生产、生活中起着十分重要的作用．

（1）如图实验中，当试管1中气体的体积为8mL时，试管2中气体体积约为____ mL，发生反应的化学方程式为____ ．

（2）水常用来配制各种溶液，硝酸钾溶液中的溶质为____．

（3）农业生产常用溶质的质量分数为10%20%的NaCl溶液来选种．现将200g25%的NaCl溶液稀释为10%的NaCl溶液，需要加水的质量为____ g．

大自然我们绝好的课堂。当你和同学们漫步绿树成荫、遍地青草的林间小路上，你会感觉到空气特别地清新和湿润，此时你会想到这是绿色植物的什么作用改善了空气的质量？ 

阅读下面短文，按要求完成各项任务。

   "Pictogram" is a compound word made from "picture" and "telegram". Pictograms are usually simple pictures, and they are often made with letters and words. A pictogram is a symbol which represents an idea or an object through an image (图像). Also, it is a kind of communication system which must be learned but is very useful in our lives. The user must learn to see, understand and remember the different pictogram symbols. There are about l, 400 different symbols at the present time.

    A Canadian named Subhas Maharaj came up with the idea for pictograms in the beginning of the 1980s. At first, pictograms were introduced to help people who had disabilities in speaking, reading, or writing. Pictograms are images of objects that are easy to see and create. Today, pictograms are used in many different ways. FOR example, there are traffic, recycling and restaurant signs, even animal symbols and so on.

    Pictograms are usually in white against a black background. The combination of white against a black background creates extremely contrast (对比) , and this makes pictograms friendlier to users. A good example of a pictogram is the public toilet symbols for "men" and women", just like the one on the left. Pictograms are a useful method of communication, and people can have fun as they learn each pictogram.