Knowledge and Skills Statement
Science concepts. The student understands and can apply the factors that influence the behavior of solutions.
Further Explanation
As an educator, it is helpful to consider how this process is used in everyday life. Dilutions are made in multiple settings and for a variety of purposes. In medicine, prescription drugs may be administered in multiple concentrations (doses) which must be correctly diluted from the original stock concentration. Household cleaning, pool, and aquarium chemicals often come in concentrated containers that must be mixed with water to the appropriate strength for the task. In an aquarium, the water chemistry must have the appropriate pH, hardness, ammonia, and nitrate concentrations for the species inside. In a swimming pool, it is important to balance chlorine levels to prohibit algal and bacterial growth without harming the people swimming. In a household, varying dilutions of products are appropriate for different levels of cleaning. One common misconception is that a more concentrated solution will be better or faster. However, if a chemical is used at too high of a concentration, it could be hazardous to human health, harmful to the object being cleaned (for example, dilute bleach will whiten, but pure bleach will burn holes through the fabric), or detrimental to the organisms in an aquarium.
Supporting Information
Research
Mojica, Elmer-Rico E., and Rita K. Upmacis. "Challenges Encountered and Students' Reactions to Practices Utilized in a General Chemistry Laboratory Course During the COVID-19 Pandemic." Journal of Chemical Education 99, no. 2 (2020): 1053–1059. https://doi.org/10.1021/acs.jchemed.1c00838
Summary: We evaluated the use of (i) videos of lab demonstrations, (ii) Microsoft PowerPoint slides with voice-over recordings that were prepared to guide students further in the particular procedure of the experiment, and (iii) kitchen-based experiments that students could perform at home for our General Chemistry I laboratory course. It was found that the videos were beneficial and the kitchen-based experiments allowed students to experience performing hands-on experiments and helped them observe and relate to concepts (such as classifying matter, making physical measurements, employing units and significant figures, preparing solutions, calculating moles and molarity, and employing separation techniques) that were discussed in the lecture portion of the course.