Introduce the demo. Students will need to measure, mix, create a “foot,” and set it up in a stable way that can sit without being disturbed for a long time.
We will model what would happen to a small "flamingo foot" if it were to sit in alkaline water for long periods of time.
Lake Natron is an alkaline lake, meaning that it is salty. Not salty like the ocean or a potato chip. The solution we'll use today is made of magnesium sulfate dissolved in water. Be sure to wash your hands at the end of the lab.
Students follow the procedure described to the right. The setup is quick; waiting for crystals can take hours to days. The rate of evaporation depends on the conditions of your classroom (ambient temperature, exposure to sunlight or heaters, humidity). Crystals only appear when a solution is supersaturated.
If you have access to a cheap digital scale, have students weigh their “feet” before and after the demo. Heavier feet have more crystals.
Because the setups are all the same in this procedure, we have called this lesson a demo not a lab. Upgrade this demo to a true "lab" by having students make hypotheses and change the conditions of their experimental setup. For example: how much water is necessary to prevent the deleterious effects of crystallization? Model the inflow of fresh water by adding variables: students could start with, say, 20mL of supersaturated solution and gather data with different experimental conditions: adding 0–10mL of fresh water per day, for example. Students would determine how much water, as a percentage of the volume of the model lake (20 mL) would counteract the evaporation that leads to supersaturation.