Design tasks tend to be ill-structured and afford many possible solutions. In addition to deciding what a design will look like, students must first identify what they want the design to do and how they will evaluate whether it meets those goals. In essence, students are asked to devise their own experiments and generate data to support or refute their assertions about what makes a good design. Design projects which result in physical, testable artifacts make many stages of the inquiry process explicit, which may scaffold students' experimental design and student reasoning about the causal factors of a design's performance. For example, students can examine a broken bridge and see where it failed, making it easier to diagnose problems in their design.
Design is by nature an iterative process.
Providing opportunity for redesign has several benefits. First, it gives students a chance to apply what they learned from building and testing earlier designs. Testing may also uncover new constraints or important properties that lead students to revise their experiments, redefining the questions, methods, and means of testing that they have been pursuing. Design projects provide a context for scientific communication. In an open-ended design context, knowledge acquired by one may be applied by all, in very different ways.