filter
![Group of learners examine color diffusion on various papers](https://nisenet.org/sites/default/files/styles/curated_list_large_cropped/public/exsci_chem_20180219_1688.jpg?h=265e640d&itok=MBn5G6FZ)
Chemistry is Colorful
In this activity, learners try to solve the mystery of which ink came from what marker by using colorful paper chromatography.
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![Hands holding square of polarizers and transparent tape](https://nisenet.org/sites/default/files/styles/curated_list_large_cropped/public/images/catalog/20140907GH1_149-1.jpg?h=6e097db3&itok=nGRgb_cw)
Exploring Materials - Polarizers
In this activity, learners experiment how polarizers affect light by using two polarizing sheets and overlapping layers of transparent tape.
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![Learners pour beads into a sieve filter to sort by size](https://nisenet.org/sites/default/files/styles/curated_list_large_cropped/public/images/catalog/8883/20110918gh192.jpg?h=4de69ae3&itok=Bn5ClXkh)
Exploring Size - Ball Sorter
In this activity, learners use sieves with different-sized holes, to sort balls by size and investigate filtering.
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![Water being poured into a Glass - iStock photo](https://nisenet.org/sites/default/files/styles/curated_list_large_cropped/public/images/catalog/8419/istock_glass_of_water.jpg?h=3deb336f&itok=_qjQOkFW)
Cleaning Our Water with Nanotechnology
In this stage presentation, learners experience demonstrations about how we can make contaminated water safe to drink using a variety of technologies.
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