I reviewed the science kit Global Water Quality: Build Your Own Water Filter ($14, Thames & Kosmos). I thought it was fun and interesting because you can turn your dirty water into clean water. I would recommend this product for people who really want to see how their tap water becomes clean water. You should be supervised by a parent when you try this.
Experiment 1: Filtering dirty water
I used a teaspoon of dirt from my house plant. I mixed the dirt with tap water and poured it into the kit’s stack of cups. When the water passed through the top cup, the bigger pieces of dirt stayed in the cup. As the water passed through the sand in the second cup, it looked like it was getting a lot cleaner. When the water passed through the wadded-up filter paper, it looked really clean. At the end when the water got to the bottom, it looked like I could drink it.
Experiment 2: Filtering colored water
I noticed that the blue water did not filter into clear water. I think it’s because the size of the particles in the blue water are smaller than the tiny holes in the crumpled-up filter. There was no change in the blue water after I filtered it.
Experiment 3: Dissolving in water
I added two spatulas of salt to the warm water. The salt sank to the bottom, and I could still see the crystals. After stirring, the salt dissolved into the water and turned the water cloudy. After two days, some of the water evaporated.
These experiments seem to work, but I would definitely use parental guidance to conduct them.