Sketching is a valuable activity to help students develop spatial skills and understand difficult geoscience concepts. Yet, sketching is rarely implemented at the introductory level due to the time needed to grade and provide constructive feedback. Our interdisciplinary team has developed a set of geoscience sketching exercises that utilize a sketch-understanding program with a built-in virtual tutor, CogSketch. Our CogSketch worksheets are designed to help students understand difficult concepts from introductory geoscience. We have incorporated the results of cognitive science research into each worksheet, highlighting the spatial skill most critical to gaining mastery of the specific topic. In particular, we utilize the capabilities of CogSketch to allow students to interact with diagrams in ways that are difficult on paper. The virtual tutor allows students to receive on-demand feedback to correct their sketch. We have created 26 CogSketch worksheets addressing topics ranging from atomic to planetary scale processes and concepts. The CogSketch worksheets were used in an introductory physical geology course at UW-Madison in Spring 2014, which typically did not incorporate student sketching. The undergraduate students had little difficulty in using CogSketch, and employed the virtual tutor to correct common mistakes. Faculty were willing to use CogSketch because it required little instructor grading time, and yet provided activities with a strong grounding in cognitive science principles.