An Investigation On Eighth-Grade Students' Understanding Of The Concepts Of Evaporation, Liquefaction And Ebullition

As for teaching content about material changing in states, it is very important for primary and middle school teaching. However, most science (physics) textbooks in different grades have no clear distinction for that content without considering the development of children's cognition ability. The writer thinks, in order to answer the question that in which grade to teach students"the three states of water"and"the three states of material"is more suitable, and also solve the problem that textbook design is to match students'knowledge level. It is necessary to make surveys on understanding concepts of evaporation, liquefaction and ebullition among students from grade three to grade nine. At the same time, we should also make surveys on whether teachers have a certain understanding of students'mastering relative concepts. Thus we can draw a conclusion by combining two results, which may provide some useful information for solving problems.This research is about grade eight students'understanding concepts of evaporation, liquefaction and ebullition, and teachers'understanding students'mastering concepts of evaporation, liquefaction and ebullition.This article was based on the research of Zhang Jingyi, a Taiwan expert. We used the test papers designed by her about concepts of evaporation, liquefaction and ebullition, and made surveys among teachers as well. Considering mainland textbooks and situation of local students and teachers, we make a bit change. Reliability and validity of the survey questionnaire are in accordance with the requirements of educational measurements and statistics. The examinees were 78 physics teachers in 19 middle schools and 924 students in 23 urban middle schools of Wuzhou.Referring to Zhang Jingyi's methods, I reread and reorganized feedbacks of teachers in the surveys, and classified students'possible ideas on each proposition what their teachers'believed into several groups and listed each of them. As for the answers of students in test papers, I reread them attentively and listed all the other possible concept types of students I thought they had in mind. Then I continuously compared these concepts with original materials, reorganized, revised students'other possible concepts I thought they had in mind, until they could reflect the whole original materials. Finally I investigated the survey on teachers, analyzed the gained effects among teachers and students, and compared the evaluated data. The research shows that:1. With rich teaching experience, the experienced teachers can point out most grade eight students'concepts of evaporation, liquefaction and ebullition. According to the research data, if 3% students got a certain idea (except chart3), teachers had pointed out the same thought as students'. Also research showed that teachers had thought students should have a certain idea in mind, but in the test, rate of grade eight students having the same idea was quite low, but this could be an important idea for students of other grades.2. The research also showed that the problem transformation from water evaporation to oil and vinegar evaporation was quite difficult for students to understand. In the tests, the correct rates fell from 87.2% to 54.22% (6.22%higher than international grade eight students average level, 48%). And the teachers'estimated rate is 74.65%, which was an effective estimation of students'idea in mind. The correct rates of proposition3"liquefaction in the opening system"and proposition7"ebullition"were less than 50%, which showed that grade eight students did not fully understand"steam". They could not imagine the state that"steam"exists in the air.3. Grade eight students'concepts of evaporation and ebullition developed better than that of liquefaction. Most grade eight students who had a higher level concept of liquefaction all have concept of evaporation, while those who had concept of evaporation didn't mean to have a higher level concept of liquefaction. This phenomenon showed that concepts of evaporation and ebullition were the base of concept of liquefaction.This article also made a comparison to Zhang Jingyi's research. From the comparison, we found out grade eight students'concept of liquefaction developed much better than grade four students', but still more than 50% students did not fully understand"steam". From the answer to the question"what is the white fog around the spout while water was in the state of ebullition?"we found that grade eight students still could not imagine the state of steam existing in the air, which was consistent with Zhang Jingyi's research results and once again proved that students'concepts of evaporation, liquefaction and ebullition were in the process of development and existence of the P's layer theory.In the article the writer proposed that establishing database to encourage cooperation, teachers should adjust their teaching plans according to students'cognition level and put an eye to students'learning will and make cognition contradictories.The paper reflexes and sums up learning samples, data collections and other aspects.