(   )形＋(   )形

(先填写上面的图形,再填写下面的图形)

Dear Seth,

    You are only three years.old,and at this point in your life you are not able to understand this letter.But some day when you1,I hope you will find something2in what I am going to share with you.

    Life can be3.There will be people in your life who won't be very nice.They'll4you because you are different,5for no good reason.You will also face heartbreak and might be6by those you love.I hope you don't have to face these too much,but such things7.

    Be open to life anyway.You'll find cruelty（残忍）and8n your journey through life,but don't let that9you from finding new things.I don't retreat（退却）from life,and don't10or wall yourself off.Be open to new things,new experiences,and new people.You will11many times,but if you allow that to stop you from trying,you will12 many chances.Do remember failure is a stepping stone to13

    You will meet many people who will try to do14than you,in school,in college,and at work.They'll try to have nicer cars,bigger houses,nicer clothes,and so on.To15,life is a competition.However,I believe life is a16.If you always try your best to17others,you are wasting your life.Learn to enjoy your life18and you will make it a journey of 19of learning and of love.

    Finally,know that I love you and always will.You are20a really wonderful journey,and I will always be there for you.

Love

Dad

用微粒观点回答下列问题：

（1）保持水的化学性质的微粒是____ ．

（2）用湿抹布擦过的桌面，一段时间后变干的原因是____ ．

（3）一定质量的水蒸气冷凝成水时，其体积变小的原因是____ ．

锅炉水垢既会降低燃料的利用率、影响锅炉的使用寿命，还可能造成安全隐患．

（1）某锅炉水垢的主要成分有CaCO₃、CaSO₄、Mg（OH）₂、Fe₂O₃，用酸洗法可除去该水垢，其基本原理如图1所示．

①酸洗时，为使水垢尽可能溶解，不宜选用的是____ （填标号）．

A．稀硫酸      B．盐酸      C．硝酸      D．醋酸

②不溶物用碳酸钠溶液浸泡时，反应的离子方程式是　____ ．

③洗出液中的Fe³⁺会腐蚀铁质管道，反应的离子方程式是____ ，因此，常在洗出液中加入具有强还原性的SnCl₂溶液，反应中的Sn²⁺与Fe³⁺的物质的量之比为1：2，Sn²⁺转化为②____ （填离子符号）．

④柠檬酸（用H₃R表示）可用作酸洗剂，溶液中H₃R、H₂R^﹣、HR^2﹣、R^3﹣的含量与pH的关系如图2所示．图中a曲线所代表的微粒的百分含量随溶液pH的改变而变化的原因是____ ．调节柠檬酸溶液的pH=4，有利于除去水垢中的氧化铁．pH=4时，溶液中上述4种微粒含量最多的是____ 　．

（2）利用下图所示装置对锅炉水（含Ca²⁺、Mg²⁺、HCO₃^﹣）进行预处理，可有效防止锅炉水垢的形成． 电解过程中，Ca²⁺、Mg²⁺在____ （填“a”或“b”）极附近形成沉淀．