题目

把下列物质的化学式按要求填写在空格内金刚石 氢气 干冰 一氧化碳 石墨 氮气（1）可用作制冷剂的氧化物是_____；（2）可用来切割玻璃的是_____；（3）具有毒性的气体是_____；（4）可用作干电池电极的是_____；（5）可用作保护气的气体是_____。 答案：【答案】CO2 C CO C N2 【解析】（1）干冰升华吸热，可用作制冷剂的氧化物是干冰，故化学式为CO2。（2）金刚石硬度较大，可用来切割玻璃的是金刚石，化学式为C。（3）一氧化碳能和人体的血红蛋白结合，导致人体中毒，故具有毒性的气体是一氧化碳，化学式为CO。（4）石墨能导电，可用作干电池电极用方框中所给单词的适当形式填空，使短文通顺、正确、连贯（每个单词限用一次）School is where we learn, make friends and grow up. But ___小题1:___ happen daily in schools across the world. We hear reports of students falling down __小题2:___ buildings while cleaning windows. Other students are hit by football on the playground. Three years ago, some students fell down on the stairs and were stepped on by小题3:___, with tragic results.We feel ___小题4:___ sorry for the loss of lives. There is _小题5:____ we can do to bring the students back, but we can try to prevent (防止) such things from ___小题6:again. You should do the following things to prevent a stampede (踩踏)。After class or school, don’t rush out at the same time. Wait until there are __小题7:____ people trying to leave.When you walk with a crowd of people, stay alert (警惕的) and ___小题8:____ your steps. Don’t play around。Be familiar with your __小题9:__ and learn where the safety exits are.When there’s pushing and squeezing (挤)， don’t move and try to hold on to something. __小题10:__ stay in a corner until the crowd leaves.