问题
单项选择题
头发突然成片脱落，脱发区头皮光滑而亮，为
A．油风
B．肥疮
C．白癜风
D．白秃疮
E．面游风
答案
参考答案：A
搜题请搜索小程序“爱下问搜题”
头发突然成片脱落，脱发区头皮光滑而亮，为
A．油风
B．肥疮
C．白癜风
D．白秃疮
E．面游风
参考答案：A
木炭在氧气中燃烧比在空气中燃烧得更旺；夏天，将食品放在冰箱里不容易腐烂．说明反应物的浓度和温度对化学反应快慢（反应速率）有影响．那么，浓度和温度是如何影响化学反应速率的？
设计方案：同学们利用双氧水和二氧化锰反应来探究上述问题，设计了下 * * 组实验．其中二氧化锰的作用是______．
| 组别 | 温度 | 二氧化锰的质量 | 双氧水的浓度和体积 | 观察产生气泡的速率 |
| 1 | 室温 | 0.5g | 5%、50mL | 反应平稳，有大量气泡产生 |
| 2 | 加热 | 0.5g | 5%、50mL | 气泡急速产生，并产生大量白雾 |
| 3 | 室温 | 0.5g | 30%、50mL | 气泡呈爆发式产生，并带出反应液 |
通过上述实验得出的结论是：
①______、
②______．
讨论反思：通过三组实验的观察与比较，你认为第______组方案比较适合在实验室制取氧气．写出发生反应的化学方程式______．
It’s Saturday morning. Tony’s sitting at the kitchen table, 36 with a piece of bread. He’s not even 37 . Is he ill? No, but he does have a 38 .He has nothing to do becau se the Internet is down. When he 39 up this morning, Tony was feeling 40 . He jumped out of bed full of plans for the 41 ahead. It would be a weekend like any other---a great weekend. But that was before he turned on his 42 and found he was 43 to go online. Having no Internet changes everything. Every weekend, Tony 44 goes online to email friends, reads the 45 to keep up with what’s happening in the world and 46 a few online chess games with his cousin Helen to finish the weekend off. The perfect weekend---online! Just as Tony is wondering how he can possibly have a normal weekend 47 the Internet, his mum walks into the 48 . “Cheer up, Tony. Don’t 49 the Internet any more, OK?” Tony makes no 50 but sighs (叹气).“Go and play chess with Helen!” Tony’s mum 51 . “Oh, yes! Helen 52 just around the corner. We can meet and play chess face 53 face for a change. Maybe this weekend won’t be so bad,” Tony 54 , as he walks to the phone. There is 55 without the Internet after all.
|