A photography light box was constructed by students using cardboard, white paper, glue/tape, scissors, and white LED lights, with dimensions of approximately 20 cm (length) x 20 cm (width) x 20 125 cm (height). The LED lights were placed on the top, covering the corners of the box, and powered by batteries. The light box was designed with a hole on the top, allowing photographs to be taken from above and from the front side. These quantitative colorimetric methods using smartphones have been reported to be effective in various research studies. In summary, the smartphone was positioned on a flat surface with its camera directed towards the light box at a consistent distance. The samples were alternatives to cuvettes. The list of apparatus can be found in the Procedure and Checklist in the Supporting Information, vide infra. Five concentrations of standard solutions were prepared by the instructors in one batch: 100 ppm Cu²⁺, 200 ppm Cu²⁺, 300 ppm Cu²⁺, 400 ppm Cu²⁺, and 500 ppm Cu²⁺. Students were asked to carefully transfer the standard solutions to separate containers. Deionized water was used as the blank. Images software (Figure ). The image files (JPG format) were transferred to a computer and opened with ImageJ software (NIH).