问题 填空题

(10分)(1) “笑气”(N2O)是人类最早应用于医疗的麻醉剂之一。有关理论认为N2O与CO2分子具有相似的结构(包括电子式);又已知N2O分子中氧原子只与一个氮原子相连,则N2O的电子式可表示为             ,它      (填“含有”或“不含”)非极性键。

(2)有以下物质:①CH4,②Cl2,③H2O,④N2,⑤C2H4,⑥C2H6,⑦H2,⑧Na2O2,⑨HCN(H—C≡N);只含有极性键且为非极性分子是__________;含有非极性键的共价化合物是__________;既有σ键又有π键的化合物是__________;

答案

 含有      

⑵   ①          ⑤⑥         ⑤⑨

(1)N2O与CO2分子具有相似的结构(包括电子式),因为二氧化碳中含有2个碳氧双键,所以N2O中也含有2个双键。又已知N2O分子中氧原子只与一个氮原子相连,所以N2O的电子式为,故含有极性键和非极性键。

(2)甲烷含有极性键,且是σ键,属于非极性分子。氯气、氢气含有非极性键,且是σ键,属于非极性分子。水含有极性键,且是σ键,属于极性分子。氮气含有非极性键,既有σ键,又有π键,属于非极性分子。乙烯含有极性键和非极性键,既有σ键,又有π键,属于非极性分子。乙烷含有极性键和非极性键,且是σ键,属于非极性分子。过氧化钠含有离子键和非极性键,非极性键是σ键,属于离子化合物。HCN(H—C≡N)含有极性键,既有σ键,又有π键,属于极性分子。

单项选择题
单项选择题

Guthrie’s contiguity principle offers practical suggestions for how to break habits.

One application of the threshold method involves the time young children spend on academic activities. Young children have short attention spans, so the length of time they can sustain work on one activity is limited. Most activities are scheduled to last no longer than 30 to 40 minutes. However, at the start of the school year, attention spans quickly wane and behavior problems often result. To apply Guthrie’s theory, a teacher might, at the start of the year, limit activities to 15 to 20 minutes. Over the next few weeks the teacher could gradually increase the time students spend working on a single activity.

The threshold method also can be applied to teaching printing and handwriting. When children first learn to form letters, their movements are awkward and they lack fine motor coordination. The distances between lines on a page are purposely wide so children can fit the letters into the space. If paper with narrow lines is initially introduced, students’ etters would spill over the borders and students might become frustrated. Once students can form letters within the larger borders, they can use paper with smaller borders to help them refine their skills.

The fatigue method can be applied when disciplining disruptive students who build paper airplanes and sail them across the room. The teacher can remove the students from the classroom, give them a large stack of paper, and tell him to start making paper airplanes. After the students have made several airplanes, the activity should lose its attraction and paper will become a cue for not building airplanes.

Some students continually race around the gym when they first enter their physical education class. To employ the fatigue method, the teacher might decide to have these students continue to run a few more laps after the class has begun.

The incompatible response method can be used with students who talk and misbehave in the media center. Reading is incompatible with talking. The media center teacher might ask the students to find interesting books and read them while in the center. Assuming that the students find the books enjoyable, the media center will, over time, become a cue for selecting and reading books rather than for talking with other students.

In a social studies class some students regularly fall asleep. The teacher realized that using the board and overhead projector while lecturing was very boring. Soon the teacher began to incorporate other elements into each lesson, such as experiments, and debates, in an attempt to involve students and raise their interest in the course.

Guthrie identified three methods for()

A. educating students

B. altering bad habits

C. avoiding undesired action

D. forming good hobbies