Inquiry-based teaching has been emphasized to enhance students' knowledge and skills and create a culture of science in science classrooms. Many teachers understand inquiry as hands-on activities, and under the pressure of content-based curriculum, they plan hands-on activities to develop students' science content knowledge described in the curriculum. This leads to science teaching as scripted performance-based teaching rather than creative and co-constructive knowledge building and problem solving. To develop inquiry abilities, students need opportunities to critically and constructively share and discuss their ideas, reasons, and alternatives in problem-solving contexts beyond managing experiments. Whole-classroom talk has been recognized as a cognitive and social tool to create a joint space of learning when teachers go beyond the traditional ground rules of the Initiation-Response-Follow-up/Initiation-Response-Evaluation (IRF/IRE) approach in classroom interactions. This study investigates examples of teacher scaffolding during whole-class discussion where an elementary teacher attempts to connect and expand hands-on activities with knowledge building, reasoning and problem-solving. This study examines specific scaffolding strategies used by the teacher during whole-class discussion and explores how the strategies develop a co-constructive learning community for students to enhance their knowledge, reasoning and problem-solving skills. The study employed a descriptive and explanatory case study model to look closely at a Grade 5-6 classroom over 4 months, with a specific focus on the dynamics of student and teacher interactions during classroom activities and discussions. During the course of the study, one teacher and 23 students worked on the science unit of electricity and electromagnetism. All science classes were video and audio taped and later transcribed to analyze the classroom talk, the teacher's scaffolding strategies, and students' learning. Research findings show that the teacher continuously demonstrated the strategies of a) probing and expanding the boundaries of thinking, b) developing collective reasoning and problem solving, and c) participating and modeling the inquiry process with students. These scaffolding strategies distributed the agency of reasoning and problem solving in a collective learning community and encouraged students to become knowledge inquirers and problem solvers. The study describes the pedagogical implications of whole-classroom talk through a discussion about how these strategies are related to and different from the widely practiced IRF/IRE approach in order for teachers to reflect and transform the practice of classroom talk into inquiry-based teaching.