问题 问答题

石油被称为“工业血液”,主要由碳、氢元素组成,是非常重要的能源.从组成上看,煤和石油都主要含有碳元素,煤和石油的最大区别是氢元素含量不同,煤中含氢元素5%~8%,石油中含氢元素11%~14%.假设只以煤为原料,使煤全部转变成石油,可以吗?说明理由.

答案

由质量守恒定律可知,化学反应前后元素的种类和质量不变,由于煤中的氢元素含量比石油中氢元素含量低,所以只以煤为原料,不能使煤转化为石油;

答:不可行,化学反应前后元素的种类和质量不变,由于煤中的氢元素含量比石油中氢元素含量低,所以只以煤为原料,不能使煤转化为石油;

完形填空

Why Exercise Is Cool?

1. Exercise Strengthens Muscles

Did you ever do a push-up or swing across the monkey bars at the playground?    小题1:   By using your muscles to do powerful things, you can make them stronger. For older teens and adults, this kind of workout can make muscles bigger, too.

2.    小题2:  

Can you touch your toes easily without yelling ouch? Most kids are pretty flexible, which means that they can bend and stretch their bodies without much trouble. Being flexible is having “full range of motion,” which means you can move your arms and legs freely without feeling tightness or pain.

3. Exercise Keeps the Balance

   小题3: Your body needs a certain amount of calories every day just to function, breathe, walk around, and do all the basic stuff.   小题4:   If you’re not very active, your body won’t need as many calories.

Whatever your calorie need is, if you eat enough to meet that need, your body weight will stay about the same. If you eat more calories than your body needs, it may be stored as extra fat.

4. Exercise Makes You Feel Good

It feels good to have a strong, flexible body that can do all the activities you enjoy—like running, jumping, and playing with your friends. It’s also fun to be good at something, like scoring a basket, hitting a home run, or perfecting a dive.

But you may not know that exercising can actually put you in a better mood.   小题5:  It’s just another reason why exercise is cool!

A.So you want to do some aerobic (有氧的) exercise right now?

B.Food gives your body fuel in the form of calories, which are a kind of energy.

C.When you exercise, your brain releases a chemical, which may make you feel happier.

D.Those are exercises that can build strength.E. Exercise Makes You Flexible

F. Exercise Makes Your Heart Happy

G. But if you’re active, your body needs an extra measure of calories or energy.

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