Lesson plan


Make crystals and understand the chemistry of dissolving and crystallization, as water is added to then removed from a solution. Separate the components of a solution through chromatography of marker pen ink. Use red cabbage dye to measure the pH of household materials.
Science content
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Atoms, Molecules (3-7)
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)

Introduce what a solution is - a mixture where the particles are evenly distributed and completely mixed up.
Do a selection of the activities to show how solutions can be made and separated (crystal making, and chromatography), and how concentration of solutions can be measured (red cabbage dye as a pH indicator).

Do the Epsom salt crystal activity, starting with showing students how the crystals dissolve in water. The epsom salts are separated again from the water when the students paint on the paper - the water evaporates and the epsom salts molecules organize themselves in a regular arrangement to make crystals. Called crystallization.

Start the sugar crystal activity. Note that the crystals will not be ready for a few days.

The chromatography activity also separates out mixtures of molecules. This method is used a lot by chemists and forensic scientists, and was used to discover the structure of insulin.
Do the Chromatography with marker pens activity. Explain what is happening in terms of molecules while students work.
Optional extension: forensic chromatography with black pens.

Introduce the idea of concentration. Students use red cabbage dye to measure the pH (or concentration of hydrogen atoms) in various household materials. Discuss how this relates to how acidic or basic materials are.


Laurier did epsom salt paintings, sugar crystals, then chromatography.
Maple Grove did Epsom salts and red cabbage, or Epsom salts and colour marker chromatography. The first time round, all three activities were done, but that was too many for a 1.5hr lesson.
Douglas did epsom salts then red cabbage (with graphing)
Kerrisdale did Epsom salt painting, then colour marker chromatography, then forensic chromatography

Grades taught
Gr 3
Gr 4
Gr 5
Gr 6
Teaching Site
Douglas Elementary
Kerrisdale Elementary
Maple Grove Elementary
Laurier Elementary