项目式学习是当前教育教学改革中的热点，是促进学生核心素养发展，培养学生适应未来发展的正确价值观、必备品格和关键能力的教学方式之一。本文以初中化学为例，对项目式学习从不同任务类型出发进行分类，并建构不同任务类型问题解决思路框架，在此基础上对不同任务类型项目式学习的教学关键问题和教学策略进行分析，最终形成了具有不同任务类型特点的项目式学习教学策略。

本研究对项目式学习的发展、内涵及特征以及教学实践、教学策略以及项目式学习中的教学策略进行了文献综述。基于研究目的，提出本研究中项目式学习作为一种教学方式，其内涵为真实问题驱动项目的开展，设计项目成果，并规划和实施项目任务以项目成果回应真实世界复杂问题的解决。在已有项目式学习分类依据的分析中，从任务类型这一角度对项目式学习展开文献研究，最终形成产品制作类、方案设计类、模型建构类以及调查研究类等四中不同任务类型。

在此基础上，进行对符合不同任务类型项目的本体及真人真事的相关文献进行扎根理论和文献研究，进而形成产品制作类、方案设计类、模型建构类以及调查研究类的问题解决思路。以产品制作类问题解决思路为例，对于产品制作主要从产品定位出发，思考产品设计与制作，进而进行优化与产品的介绍。对于产品定位而言，需要关注产品的需求分析；对于产品设计则需要考虑产品原理分析、工艺流程以及设计图的绘制；在产品制作中要对制作材料进行选择并按照顺序组装；在产品优化中需要考虑产品的测试评价以及完善；最后通过产品介绍，体现产品使用说明以及维护。

由于项目式学习是以真实问题驱动，并在真实问题的解決中不断建构对核心知识、学科思想方法等的认识，而不同任务类型问题解決思路的建构为不同任务类型项目式学习更好的实施和开展提供了支架和基础，其为教师设计项目提供帮助，也能够促使学生从真实问题解决的角度认识项目的价值和意义，体会学科核心知识、思想方法等的重要性。故而在不同任务类型问题解决思路形成的基础上，通过扎根理论、文献研究等对符合不同任务类型项目式学习的教学实践及专家指导等文本信息进行研究分析，形成具有不同任务类型特点的项目式学习教学关键问题，得出具有针对性的教学策略。以产品制作类项目为例，本研究中形成了“如何进行产品需求分析？”“如何引导学生初识产品工作原理？”等8个主教学关键问题，形成了“如何引导学生课前调研了解产品情况？”“教师如何使用素材说明产品需求？”等21个子教学关键问题；进而结合教学目标和学生学情及能力基础的分析，形成了“明确产品制作需求”“分析讨论产品工作原理”等8个主教学策略，形成了“学生汇报产品调研情况，教师追问调查思路”“真实生活问题说明产品需求”等35个子教学策略。

通过对产品制作类项目、方案设计类项目、模型建构类项目以及调查研究类项目的教学关键问题及教学策略的研究，分别形成由教学目标、学生学情、问题解决思路以及课型四个维度建构所得的四种不同任务类型的项目式学习教学关键问题、教学策略的分析框架 。对于分析框架而言，一方面其可以用于不同任务类型项目式学习中教学关键问题和教学策略的提炼，另一方面可以通过该分析框架的各个维度分析，检验后续相关研究中提出的不同任务类型的教学关键问题和教学策略对不同任务类型特点的凸显情况。

Project-based learning is a hot topic in current education and teaching reform. It is one of the teaching methods to promote the development of students' core qualities and cultivate students' correct values, essential qualities and key abilities to adapt to future development. Taking chemistry in junior high school as an example, this paper classiifies project-based learning from different task types and constructs the thought frame for solving problems of different task types. On this basis, it analyzes key teaching problems and teaching strategies of project-based learning of different task types, and finally forms project-based learning teaching strategies with characteristics of different task types.

This study reviews the development, connotation and characteristics of project-based learning, teaching practices, teaching strategies and teaching strategies in project-based learning. Based on the research purpose, project-based learning is proposed as a teaching method in this study. Its connotation is that real problems drive the development of projects, design project results, plan and implement project tasks, and project results respond to the solution of complex problems in the real world. In the analysis of the existing classification basis of project-based learning, literature research on project-based learning is carried out from the perspective of task type, and four different task types including product making, scheme design, model construction and investigation and research are finally formed. On this basis, grounded theory and literature research are carried out on ontology of projects of different task types and related documents of real people and events, so as to form problem-solving ideas of product making, scheme design, model construction and investigation. Taking product making problem solving ideas as an example, product making mainly starts from product positioning, thinking about product design and production, and then carries on optimization and product introduction. For product positioning, it is necessary to pay attention to the demand analysis of the product; For product design, it is necessary to consider the product principle analysis, process flow and design drawing. In the production of products to select the production materials and assembly in order; Testing, evaluation and improvement of products should be considered in product optimization. Finally, through product introduction, product usage instructions and maintenance are reflected.

Because project-based learning is driven by real problems, and the understanding of core knowledge and discipline thinking and methods is constantly constructed in the solution of real problems, the construction of problem-solving ideas of different task types provides a scaffold and foundation for the better implementation and development of project-based learning of different task types, which provides help for teachers to design projects. It also enables students to understand the value and significance of the project from the perspective of real problem solving, and experience the importance of core knowledge and thought methods of the subject.On the basis of the formation of problem-solving ideas for different task types, through grounded theory and literature research, the teaching practice and text information guided by experts in line with different task types of project-based learning are studied and analyzed, so as to form the key issues and analysis framework of project-based learning teaching with characteristics of different task types.Taking product production projects as an example, this study formed "How to conduct product demand analysis? "How to guide students to understand how products work for the first time? And other 8 key teaching questions, formed the "how to guide students to understand the product before class research?" "How can teachers use materials to illustrate product needs?" And 21 sub-teaching key problems; Furthermore, combined with the analysis of teaching objectives, students' learning situation and ability basis, eight main teaching strategies were formed, such as "Clarifying product production needs", "analyzing and discussing the working principle of products", and 35 sub-teaching strategies were formed, such as "students report product research situation, teachers ask for investigation ideas" and "real life problems explain product needs".

Through the research of the key teaching questions and teaching strategies of product making projects, scheme design projects, model construction projects and investigation projects, the analysis models of the key teaching questions and teaching strategies of project-based learning of four different task types are formed, which are constructed from the four dimensions of teaching objectives, students' learning situation, problem solving ideas and class type.