We discuss how to reduce the incongruence between the outcomes (both cognitive and affective)
of the conventional secondary chemistry curriculum and what is to be attained: the meaningful
connection of students’ learning to daily life and societal issues. This problem is addressed by a
design study with one curriculum unit about “Water Quality”. With several research cycles using
developmental research, we developed an emergent understanding about an instructional framework
for curriculum units that embodies a coherent “need-to-know” principle and is based on
authentic practices. Using this framework we show with some other examples how a context-based
chemistry curriculum can be constructed based on the developed “need-to-know” principle.