Resealable plastic bags
Instructions:1. Fill two resealable plastic bags with a generous amount of soil.
2. Add a handful of grass seed and some water so the soil is moist but not soaked.
3. Close the bags and shake them so the soil and seeds mix.
4. Hang one bag in a window with southern exposure.
5. Hang the other bag in a window with northern exposure.
6. Both airtight bags will produce water droplets, and the continued "rain" will keep the soil wet.
7. Watch the bags to see which bag sprouts the seeds first. Encourage the children to try to explain why the seeds emerge first in the bag with southern exposure.