How to measure epsom salt crystal growth

[deleted-307147]

My third grader is doing this project. She wanted to test how temperature affects the growth of epsom salt crystals. She has a small bowl of a saturated solution sitting in the refrigerator, one on the counter top and another outside. She needs to measure the crystal growth in metric units and thought using a kitchen food scale would work. Crystals have started to grow from the refrigerator sample but the weight in grams of the bowl with the saturated solution is the same as when she started, eventhough there are lots of spikes of crystals. How does she weigh the crystal growth? She has the weight of the bowl empty and the bowl with the saturated solution before crystal growth. She thought she could just use the new weight and subtract the initial weight to see the growth in metric units. Please help!

[bfinio]

Hi sis328,

The problem with your measurement method is that the crystals are forming from ingredients that are already in the bowl. So, even though those ingredients change form (from salt in saturated solution to solid crystals), the total weight of the bowl will not change, because the salt was already in the bowl. To weigh the crystals you would actually need to remove them from the bowl, dry them off, and weigh them separately. I haven't done this project so I'm not sure how fragile the crystals are or how feasible that is. Another approach might be to use a ruler to measure the approximate size of the crystals. I know they will have an irregular shape, but you could try to measure their average width.

Also - I'm not sure how long the project takes, but water will gradually evaporate from the bowl, which will also affect the weight if you try to weigh the entire bowl. So to accurately measure the weight of the crystals, you need to just measure the crystals by themselves.

If you're doing a specific project on the Science Buddies site, could you provide a link to it?

Thanks,

Ben