对已学过的知识进行梳理、归纳，是中学生应该掌握的学习方法．
请你完成下列对化学反应的归纳：（举例写出文字表达式）化学反应的本质特征______．
化学反应的类型______
化学反应的本质是有新物质生成，化合反应是指由两种或两种以上的物质相互反应生成一种物质的反应，用字母可表示为：A+B→AB例如：硫+氧气
二氧化硫；分解反应是由一种物质反应后生成两种或两种以上的化学反应，用字母可表示为：AB→A+B例如：过氧化氢点燃
水+氧气．二氧化锰
故答案为：生成新物质；化合反应：A+B→AB例如：硫+氧气
二氧化硫；分解反应：AB→A+B例如：过氧化氢点燃
水+氧气．二氧化锰
You have been thinking about it all week. It kept you awake last night. Now, as you walk to the front of the class, your throat is dry and your stomach feels funny. ___小题1:__. However, by making a small preparations and rehearing(预演)carefully, you can be a public speaking star, too. ___小题2:__. Being excited about your topic is necessary for all the good speeches, so it's important to choose carefully. If you enjoy your topic, your audience(观众) will, too. Even if you are given a topic, try to find something about it that it is exciting or funny. Next do some research. Don't just research your topic. ___小题3:__. If you can, study videos of a great speaker to see how they move, speak, and pause(停顿). Copying their style will help you to write a great speech. After researching, it’s time to write your speech. During this stage, think of your audience all the time. Entertaining your audience is important. It helps you relax if you know that your audience is enjoying your speech. Finally, rehearse. You really need to rehearse a lot. Measure your speech with a watch, and practice in front of a mirror. ___小题4:__ . If you have followed all these steps, you should be ready for your audience. Good luck!
|