题目

右图中两块金属片互相刻画后，在纯铜片上留下明显划痕，该实验探究的目的是             ；写出一个有铜参加的置换反应的化学方程式                                       。 答案： 比较黄铜和纯铜的硬度； Cu+2AgNO3===Cu(NO3)2+ 2Ag29、I am the Earth．Once I was in good health，but now I feel quite uncomfortable． Yesterday I went to see Doctor Moon．She asked me，“What's wrong with you，Mr. Earth?” I told her，“My children--the people--have destroyed the ozone（臭氧），so the sunshine is too strong．Now I have a high fever．Many trees have died．The dust（灰）always gets into my eyes．I smell the waste gas of cars every day．I can't take in clean air．I often suffer from earache，because I hear loud noises all the time．” “Oh，Mr. Earth，” said the Moon，“Your illness is so serious．You must have a good rest and drink a lot of water every day．” “That’s fine，but it often rains acid rain（酸雨），so I have no clean water to drink at all．” I replied． “That's terrible! I'm very sorry，but I can't help you．” The Moon was very sad． Oh，dear! What can I do? Who can save me? 1．Who did Mr. Earth see yesterday? A．Doctor Moon．   B．Doctor Sun．        C．His children． 2．Why does Mr. Earth have a high fever? A．the sunshine is too strong．                         B．He suffers from earache． C．The dust gets into his eyes． 3．Who are Mr. Earth’s children? A．The trees．          B．The cars．           C．The people． 4．Why does Mr. Earth have no water to drink? A．Many trees have died．                               B．The ozone has been destroyed． C．It often rains acid rain． 5．Which of the following is True? A．The Earth is ill．                                        B．The Earth is in good health． C．The Moon can help Mr. Earth．