问题 选择题

下列各组选项中,有错误的一组是

A合金不锈钢、焊锡、生铁
B碱类烧碱、纯碱、熟石灰
C干燥剂浓硫酸、生石灰、氢氧化钠固体
D合成材料合成橡胶、合成纤维、塑料
 

答案

答案:B

题目分析:根据物质的有关分类方法判断。

A、根据合金的概念,金属与金属或金属与非金属形成的混合物,可知不锈钢、焊锡、生铁都属于合金,故A正确;

B、纯碱是由金属离子钠离子和碳酸根离子组成的盐,而不是碱,故B错误;

C、浓硫酸和氢氧化钠固体都有吸水性,生石灰会与水反应,都可做干燥剂,故C正确;

D、合成材料又称人造材料,是人为地把不同物质经化学方法或聚合作用加工而成的材料,故D正确。故选B

点评:理解和熟练掌握合金、碱、合成材料的概念以及干燥剂的种类,是解题的关键,在平时的学习中要加强识记。

填空题
阅读理解

阅读理解。

     Compared to adults, children seem to be moving constantly. So it's no surprise that most parents who

are quizzed about their child's physical activity level describe their children as fairly active. But a new

study of nearly 2000 British school children suggests that many parents overestimate the amount of

physical activity their children are really getting.

     The researchers equipped 1892 British school children, ages 9 and 10, with accelerometers that

measure all physical  activity  during  a  given  time  period.  The research, known as the Speedy study

collected the exercise data from children at  92  schools  in  Norfolk, England, between April and July

2007.

     A child was regarded inactive if he or she recorded less than an hour a day of physical activity.

Although the majority of children studied were getting enough physical activity, a sizable minority of

children were not. Overall,39 percent of girls and 18 percent of boys studied were getting less than an

hour of physical activity each day.

     But if you asked the parents of the inactive children to describe their child's activity level, the vast

majority-80 percent-described their children as fairly or very physically active, according to the findings

published in the American Journal of Preventive Medicine. Interestingly, the children themselves had

more awareness about their lack of physical activity. Overall, 40 percent of children overestimated their

physical activity.

     But it wasn't the parents of overweight children who were most likely to guess wrong about physical

activity levels. The parents who were most out of touch about their child's physical fitness were more

likely to  have children who were slim. Parents of girls were also more  likely  to  overestimate  physical 

 activity.  The  researchers noted that parents should be educated about the importance of physical

activity for children even if the child is not overweight.

     "Parents of slim children appear to assume that  their children are adequately active." the study

authors  reported. "Increasing awareness regarding health benefits of physical activity beyond weight

control might  help have a correct idea of physical activity levels and encourage behavior change."

1. According to the Speedy study, what kind of children   can be judged physically inactive?

A. Slim children.

B. Children with less than an hour a day of physical activity.

C. Overweight children.

D. Children out of touch with their parents for a long time.

2.What does the writer probably mean by saying "a sizable minority of children were not" in Paragraph 3?

A. The amount of children's physical activity is far from the writer's satisfaction.

B. Only a small number of children were not getting enough physical activity.

C. A small number of children didn't overestimate their physical activity.

D. The minority of children were not studied at all.

3.The passage is intended to_______.

A. encourage parents to fairly judge their children's physical activity levels

B. persuade parents to keep an eye on their children's weight

C. urge children to wear accelerometers during exercise

D. advise parents to keep in touch with their children