问题 填空题

(6分)用化学符号表示:

①3个氦原子_________;②水分子________;

③人体内含量最多的元素_________;地壳中含量最多的金属元素_________;

④ 2个镁离子________; 画出镁离子的结构示意图            

答案

考点:

专题:化学用语和质量守恒定律.

分析:本题考查化学用语的意义及书写,解题关键是分清化学用语所表达的对象是分子、原子、离子还是化合价,才能在化学符号前或其它位置加上适当的计量数来完整地表达其意义,并能根据物质化学式的书写规则正确书写物质的化学式,才能熟练准确的解答此类题目

解答:解:①原子的表示方法就是用元素符号来表示一个原子,表示多个该原子,就在其元素符号前加上相应的数字.所以3个氦原子,就可表示为 3He

②一个水分子是由两个氢原子和一个氧原子构成的,故水分子的化学式为H2O

③人体内含量最多的元素是氧元素,符号为 O;地壳中含量最多的金属元素是铝元素,符号为 Al

④离子的表示方法:在表示该离子的元素符号右上角,标出该离子所带的正负电荷数,数字在前,正负符号在后,带1个电荷时,1要省略.表示多个离子在离子符号前面加数字,故2个镁离子符号为2Mg2+:镁离子是镁原子失去两个电子形成的,镁离子结构示意图为:

故答案为:①3He;②H2O;③O; Al;④2Mg2+; 

点评:本题主要考查学生对化学用语的书写和理解能力,题目设计既包含对化学符号意义的了解,又考查了学生对化学符号的书写,考查全面,注重基础,题目难度较易.

阅读理解

British researchers are looking for volunteers willing to eat a piece of chocolate daily for a year in the name of science. The trial(实验) will explore whether flavonoids (类黄酮) found in chocolate and other foods can reduce the risk of heart disease.

“We are looking at a high risk group first,” said Aedin Cassidy, a biochemist who will lead the study.

Previous studies have suggested dark chocolate is rich in the beneficial flavonoids linked with heart health, but experts note the high sugar and fat content of most commercially available chocolate might cancel out some of the advantages. Other research has also shown dark chocolate appears to lower blood pressure, improve the function of blood vessels (血管)and reduce the risk of heart attack.

This has encouraged companies to market specific products containing dark chocolate. Mars Inc has introduced Cocoa Via, a line of dark and premium chocolates that plays up such health advantages.

Cassidy said her team will also publish findings in the American Journal of Clinical Nutrition showing that flavonoids found in soy and cocoa appear to have the strongest effects of reducing risk of heart disease.

The next step will organize 150 women volunteers with a specific illness. The researchers will look at whether flavonoids help reduce blood pressure, cut cholesterol levels and improve the condition of blood vessels.

Half the women in the year-long study will eat chocolate containing 30 grams of flavonoids found in soy, cocoa and other fruits and vegetables. The others will get chocolate without the active flavonoids.

“This could help doctors give advice to patients on the type and amount of foods to eat to reduce heart disease risk—and it does not necessarily need to be chocolate,” Cassidy said. “If this trial works we will be able to advise on a whole range of foods. People won't have to go around eating specially designed chocolate.”

1. What is the best title for the passage?

A. Volunteers wanted for chocolate study.           B. Chocolate is good for health.

C. A new research on heart attacks.                 D. Flavonoids found in chocolate.

2. What’s the purpose of the trial?

A. To test the advantages of a new kind of chocolate.

B. To find cures for heart disease.

C. To discover how to control blood pressure.

D. To explore the advantages of flavonoids.

3. From Paragraph 3 we can infer that __________.

A. Cassidy’s team has done several studies on chocolate

B. dark chocolate has proved beneficial to health

C. people should eat much chocolate with high sugar and fat

D. most commercially available chocolate doesn’t contain flavonoids

4. Which of the following statements is TRUE according to the passage?

A. All the volunteers will eat the same chocolate.

B. CocoaVia is a company that produces dark chocolate.

C. People who want to take part in the trial should be healthy.

D. Soy, cocoa, some fruit and vegetables contain flavonoids.

问答题 简答题