Abstract concepts are difficult because students cannot connect them to prior knowledge. The pedagogical approach concreteness fading introduces abstract concepts through a concrete representation grounded in students' real-world knowledge. As instruction progresses, perceptual information is removed until the abstract representation is reached. This thesis investigates concreteness fading in the programming domain with university-level students (N = 50). We created a lesson to teach the concept of 'for-loops', in the Python language. The study used a between-subject design with two conditions. The experimental condition included a lesson starting with a concrete representation of the concept depicted as an animation, that gradually faded into its abstract representation, namely the Python code. The control condition included a traditional lesson with only the abstract code. The intervention was implemented with an online computer tutor built using the Cognitive Tutor Authoring Tools (CTAT) package. While learning increased overall, there was no significant effect of condition.