问题 解答题

回答“探究种子的成分”实验中的问题:

(1)取一些干燥的小麦种子,装进干燥的试管里,用酒精灯均匀加热,试管内壁上出现______,说明______.

(2)取10粒干燥的小麦种子,放到石棉网上用酒精灯烧烤.种子起初变焦后变黑,这种物质是______,随后就燃烧起来,燃掉的物质是______,剩下来的物质是______,呈______色,这说明______.

(3)将少许小麦面粉加水和成面团,用纱布包起来在清水里用手反复揉挤,从纱布里渗出来的白色物质是______,纱布内剩下的______色物质是______,这说明小麦种子里含量较多的两种有机物是______.

(4)切下烘烤过的小麦种子的胚,放在白纸上压挤,白纸上出现______,这说明______.

答案

种子的成分包括有机物(淀粉、蛋白质和脂肪)和无机物(水和无机盐),(1)“探究种子的成分”的实验中取一些干燥的小麦种子,装进干燥的试管里,用酒精灯均匀加热,试管内壁上出现小水珠,说明种子中含有水分.

(2)取10粒干燥的小麦种子,放到石棉网上用酒精灯烧烤.种子起初变焦后变黑,这种物质是碳 点燃后有机物燃烧变成二氧化碳和水散发掉,水受热蒸发,剩下来的不能燃烧的灰白物质就是无机盐.

(3)白面主要成分是淀粉,其次是蛋白质.淀粉是水溶性的,可以从纱布中露出溶于水,形成浊液.蛋白质不溶于水留于纱布内,其质地粘稠.将少许小麦面粉加水和成面团,用纱布包起来在清水里用手反复揉挤,从纱布里渗出来的白色物质是淀粉,纱布内剩下的黄白色物质是蛋白质,这说明小麦种子里含量较多的两种有机物是淀粉和蛋白质

(4)切下烘烤过的小麦种子的胚,放在白纸上压挤,白纸上出现 油迹,这说明 种子中含有脂肪.

故答案是:(1)小水珠;种子含有水分 (2)碳 有机物;无机盐;灰白;种子中含有无机盐 (3)淀粉;黄白;蛋白质;淀粉和蛋白质 (4)油迹;种子中含脂肪

阅读理解

阅读理解。

     Meals at the family dinner table could be the key to preventing a generation of  teenage girls from

developing eating disorders (紊乱).

     New research shows girls who regularly have family meals are much less likely to adopt extreme

weight-control behaviors such as vomiting, and using diet pills.

     The research, published in the international journal Archives of Pediatrics and Adolescent

Medicine, surveyed students aged 13 to 17 in 2003 and followed them up five years later. Regular

family meals were found to have a protective effect regardless of the age, weight, socioeconomic status,

dieting habit or relationship with the family.

     Belinda Dalton, director of the eating disorder clinic The Oak House, said eating with family helped

"normalize" young people's relationship with food.

     "When teens are feeling that they are not managing, they turn to something that they can control and

food is something available and accessible for them to control. Clearly, if they are sitting with their family

on a regular basis, then their family can be more in control of their eating," Ms Dalton said.

     "It's about young people feeling connected within their family, and that builds self-esteem and a sense

of worth and works very actively against someone developing an eating disorder.

     An eating disorder expert, Kirsty Greenwood, said meal times were often difficult for sufferers. "It's

typical that they feel very ashamed of their eating habits and often won't eat with other people. Perhaps

it's because they haven't experienced the important of the family meal while growing up," she said.

     The study found eating regular family meals made no difference to the future eating habits of boys.

1. The author writes this passage with the purpose of _______.

A. stressing the necessity of family meals for the teenage girls

B. showing the results of a research

C. providing some suggestions on family dinner

D. presenting the difference in eating habits between boys and girls

2. Which of following is NOT a benefit of regular family meals?

A. They decrease the trend towards extreme weight control behaviors

B. They can help girls to have a better relationship with food

C. They can help girls to work against the development of an eating disorder.

D. They provide girls with the chance of getting control of food.

3. What does the underlined "that" in Paragraph 6 refer to?

A. Young people

B. Having a good relationship with the family

C. Feeling connected with the family

D. Self-esteem and a sense of worth

4. We can infer from the text that ______.

A. Ms Dalton advises parents to get children under full control

B. Kirsty Greenwood suggests that the time for meals be fixed

C. the effect of regular family meals on boys differs from that on girls

D. experience is more important than indirect knowledge

单项选择题