Chemistry is a kind of natural science based on experiments. The fantastic  chemistry experiment will stimulate students’ intellectual curiosity and contribute to their development of research capacity. In china, due to limited teaching aids and classroom time, the operation of chemical experiments are often carried out in the form of cooperative small group. 

Cooperative small groups on learning currently receive increased attention in classrooms. Cooperative learning is a classic idea in education, which refers to classroom techniques in which students work on learning activities in small groups and receive rewards or recognition based on their group’s performance(Slavin, 1981).  In china, cooperative small groups on learning as classroom techniques have been widely used in schools in recent years. Research on cooperative learning has focused on small groups of students working on academic tasks. The key feature distinguishing cooperative settings from other learning settings is interaction among students(Webb, 1982).

However, research showed that only 25.5% of teachers emphasize the cooperation and interaction among students during the operation of chemistry experiment(Zhou, 2012). Moreover, the rules of grading of the National Chemical Entrance Examination for Senior High School Entrance Examination are oriented exactly on "operability", with less attention paid to students' use of scientific methods, not to mention the cooperation between students in scientific experiments. It seems that very few teachers have considered the interaction or cooperation issues in the operation of chemistry experiment. 

1. Objectives and research questions

Thus this study is to explore the characters of small group interaction in chemistry experiment context, using the participation structure as a theoretical framework.

I specifically pursued four research questions:

• What are roles of teachers and students in small group in chemistry experiment?
• How students interacts or coperates with each other to complete the task?
• Hpw teacher interacts with students in chemistry experiment?
• How their interaction(student-student; teacher-student) infulences the group achievement?

2. Theoretical Framework

Participation Structure is a classical theoretical framework in the sphere of interactional analysis. The idea of participation structure is proposed by Goffman. In Goffman's puppeteering metaphor, a speaker animates self or other as a figure or character by simple linguistic means. Through talk about each other, speakers give each other participant roles and social identities relevant to the moment((O'Con-nor & Michaels, 1994). Participation structure is thought to help clarify how people establish roles and relationships in conversation and is therefore often used in face-to-face interaction analysis, especially in formal school contexts (eg, classrooms) .

In Erikson(1996), I find a further development of participation structure that as teachers and students interact in classrooms, they construct an ecology of social and cognitive relations in which influence between any and all parties is mutual, simultaneous, and continuous. Although teachers in group discussion may attempt to en- force a participation framework of successive dyadic teacher-student exchanges, often the conversation is more complicated than that. Therefore, Erikson believes that the relationship between the participants is more worthy of attention than the focus on the role of participants in the interaction.

Through the participation structure, we can find that the participatory relationship in interaction becomes visualized. In such a mobile structure, participant participation or engagement is not only manifested through discourse, but also through physical activity such as body posture, eye contact, gestures, etc., and even more in-depth representation of the interaction between the participants relationship.

This paper analyzes one case of 5 students interacting during one chemistry lesson. The lesson took place in a 9th grade classroom. This middle school was located in Minghang district in Shanghai. The class includes a chemistry teacher (female) and 25 students. The author conducted an observation study in this class in December 2017 and collected audio and video recordings of this class. The case took place in the "Carbon Dioxide Attributes" module, where teacher divided the class into five groups of five students, each experimentally exploring the different properties and uses of carbon dioxide . In this 40-minute class, I mainly focused on one of the experimental groups. In this group, the group members are: Xiao Hong (female), Xiaoqiang (male), Xiaoyong (male), Xiaoming (male), Xiaofang (female) . Their experimental equipment are beakers, candles, alcohol lights, matches, wood, carbon dioxide-filled gas bottles (with glass cover). The purpose of their experiment was to find out that carbon dioxide is non-flammable, non-flammable and denser than air (oxygen) by observing the extinguishment of the candle after it has been poured into the carbon dioxide gas. The data in this paper is one segment of the transcriptions of the entire videotapes.

To some extent, small group in chemistry experiment is very similar to the medical surgery. These 2 contexts contain some same characters: limited operating space and operating equipment, each team member with division of labor and tasks, task-oriented type of interaction. In the surgical team, there is usually a specialist doctor (who is in charge of guidance), a surgeon, an assistant surgeon and equipment nurses(Bezemer et al., 2011). In the interaction analysis of small group learning in chemistry experiment, this research finds that teacher and students play different roles during the chemistry experiment. Teacher is somehow a “specialist doctor”, who gives the team a whole picture about the experiment and provide some instructions or advises during the operation. Xiaoming and Xiaofang are the surgeon, Xiaoqiang and Xiaoyong are assistant surgeons and Xiaohong is the equipment nurse. A sucessful surgery relies on the cooperation of each member in the surgical team. In this chemistry experiment, its internal participation structure and interactive ecology are extremely rich and complex. Seemingly Xiao Ming and Xiaofang led group experiments, but in fact all the team members need to work together to complete the task. During the experiment, Xiao Ming and Xiaofang kept asking “What shall we do?”, and the group members offered their help queitly or non-verbally. At the same time, the instructor's guidance has an extremely important influence on the entire group's experimental process. In this case, this study argues that teacher’s instructions negatively affected the group experiment. The study finds that each subtle operation occurs, there will be one or more participation structure, and these structures are often formed by "help". So this article advocates that teachers should not only pay attention to individual students' accuracy in operation but should pay due attention to the interaction and cooperation among group members.

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