Inexpensive items such as coffee filters, fingernail polish remover, and rubbing alcohol are used in this fun activity. In an extension, students apply scientific concepts to guide and form a testable hypothesis on how one can identify which black marker was used to produce a prepared chromatogram. Students conduct an investigation using different chromatographic systems, including using different mobile phases, different stationary phases, and different pigments and other colorful mixtures. Using logic and evidence from their investigations, students formulate and revise scientific explanations and models. Students compare chromatographs to determine which colors of pigment were used to make different brands of markers, which is the fastest-traveling color for a given solvent, how pigments travel up filter paper, and why the order of pigments is different for different solvents.
Students use mathematics to calculate the retention factor for each pigment.
A mixture of substances often can be separated into the original substances using one or more of the characteristic properties. The physical properties of compounds reflect the nature of the interactions among their molecules. Due to intermolecular forces between molecules of various pigments, some pigments can often be separated from a mixture. Page maintained by Steve Gentle, Research Associate.