Summary Do a series of activities showing water as a medium that carries, mixes and separates chemicals, which links the life and the rocks of planet earth. Science content Chemistry: States of Matter, Properties of Materials (K-7) Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6) Earth/Space: Water cycle, Water conservation (2) Earth/Space: Sustainable practices, Interconnectedness (2, 5, 7) Activities in this lesson Epsom salt crystal painting Red cabbage dye (and pH indicator) Chromatography with coloured marker pens Procedure Introduction: Water itself is essential for life on earth. It also carries chemicals that nourish life, form our landscape and makes things change. Students rotate through three activities, with discussion at the end on how they relate to water. 1. Growing epsom salt crystals This water carries a salt. When the water evaporates it leaves the salt behind, which organize into crystals. The longer the solution takes to dry, the longer the crystals are. Big picture: Water carries salts, minerals and nutrients, bringing them to new places. They are used by living things, and are deposited as mineral crystals or rock formations. 2. Red cabbage dye Water can be used to extract dye molecules from plants. Discuss indigenous dyes as the class makes red cabbage dye as a group. Some dyes, including this red cabbage dye, can change colour depending on other components of the water (acids and bases). The different colours made can be used to dye cotton cloth or yarn. Big picture: Water carries the colours in plants. Plants can be crushed to bring out the colours in them, which can be used as dyes. Some dyes change colour depending on the amount of acid or base in the water. Many colours in living things are dependent on the amount of acid or base in the water in them. 3. Separating colours with chromatography Dyes are often mixed together to make new colours. We can use water to separate them. The different colours making up the ink are pulled along by the water to different extents, so some move faster and some move slower. The different rates mean that the colours are separated out. Big picture: water carries along rocks, silt and chemicals. Depending on how easily they are moved by the water, they will be deposited in different places. Grades taught Gr K Gr 2 Gr 3 Gr 4 Gr 5
