九年级下英语遣词造句

Students in solving chemical problems often lose points, points the reason to roughly the following three conditions:1, simply do not know how to solve;2, know the general idea, seems to have seen, but the solution is not complete or incomplete right; 3, can list formula, but was unable to calculate to the final results.For the first student convinced, admitted that he wouldn't do in the later study pay attention to make up for the deficiency of; Most of the second student, thought to be "carelessness jingzhou", by implication, problem solving skill, just careless, in the future, as long as they are more careful. For the third student also admits that he is poor mathematical basis. To sum up, want to measures not fine, don't want to coarse always thick, very vexation to teachers and students., so repeatedly, careless accident, but if appear, behind it there is a certain inevitable factors, the inevitable factors generally have the knowledge and the knowledge factors.A, knowledge factor:(1) cognitive structure is unstable.Example: a, g, a solution containing a solute g, b is the solute quality mark for ___ %.There are more students to answer this question, get the result of the b/a, and the correct answer should be 100 b/a.This knowledge teaching seems to be related to the percentage of the first mathematical problems, rough look at this problem seems to be the first mathematical knowledge, but why students solutions for this problem so much wrong, after investigation, found that students solve such problem, in the first type of 100% as 1 and not usually write formula, but the 100% must be written in this topic. It shows that the students on the mastery of the knowledge, is not firmly "welding" on the cognitive structure, in the actual process lack of overall cognitive knowledge.In view of this, in the teaching process should pay attention to knowledge too warm at any time, the review and reconstruction of mathematics knowledge, timely points out differences and relationship between old and new knowledge system, changes in the new system and old knowledge, and arrange proper practice, and follow the forget rule, quickly before they are slow to close after the first height stimulation of these welding points again and again.(2) lack of logic of thinking, reasoning, a loophole.Example: something in oxygen combustion produces CO2 and H2O, the object must contain... elements.Have students answer contain C, H, O three elements. In fact must contain elements of C, H, element may contain O. On the topic of coarse seemingly careless students, and from the deep analysis, in fact is the incomplete understanding of the law of conservation of mass.To such errors to guide students to be familiar with the basic concepts, understanding of the concept of internal and external, and similar to the students to practice as much as possible, let the student through practice, deepen the application of the concept.Second, the non intellectual factors:(1) the bad habits.Operation error is to solve the problems of chemical calculation, some of the reasons for operationerror, according to the survey, part from students a contempt for such calculations. Such as 45 + 35 = 70 (wrong) think that such a topic is a simple, thick and a calculate calculate settlement and such errors even in the review process, it is hard to detect errors, the second is from scratch paper, more students in the draft is "go", here to write one, where a written, or in the same place repeatedly robbed alter, wrote later full paper also find empty pin, the smoke such errors produced by interference, such as losing points, etc.To this, students in the process of calculation, want careful, scratch paper will in an orderly way, such not only difficult to go wrong, wrong is easy to check. Teaching, to tell the student the bad habit is an important factor lead to carelessness caused by wrong.(2) psychological quality unstable.Some students played poorly, when the problem solving, often by some kind of struggle, seems to be discovered about the path, but a slight negligence do not know how to start again, for this kind of students often should cultivate their "three by a slow 2 see" habits, regular exercise at ordinary times the "better not arrogant, don't boast about" psychological quality, tell them "I don't careless, you hard I difficult I am not afraid of difficult", so often accept the effect of the "mountain". Behind, in short, careless, actual complicated and profound background of the knowledge and the knowledge factors and interaction in certain cases, as a teacher to guide students to in-depth analysis, suit the remedy to the case, in order to make the student to obtain "immunity".。