Student learning and engagement happens within a sweet-spot of rigor - when students are required to dig deep to access their potential, but with enough opportunity for success that they can imagine this potential, even if still struggling to access it. Science when taught in this sweet-spot, differentiated for each student and her interests, is a great way to connect science with identity. When students learn to embrace scientific challenges, and become proud of overcoming these challenges, their confidence and self-identity becomes at least partially rooted in science. This is how my interest in science was developed and maintained in high school, college, and beyond.
Learning science is interesting to me, but it wasn't always so. Using science is what drew me to it, and motivated me to learn it. Problem based learning, exciting lab experiments, thinking about the future... That's what hooked me, and that's what got me to invest in studying concepts. At a certain point, studying concepts became interesting and rewarding in itself; but teachers cannot expect students to share their interest without earning their interest.