#2 Filtration Experiment

filtration-experimentThis post contains affiliate links. I was compensated for my work in writing this post.

Today we will be doing a fun filtration experiment where salt goes through a filter like magic, while sand remains behind. This is one of the experiments in the book Christian Kids Explore Chemistry by Bright Ideas Press. The book provides a chart to fill in as we examine the salt and the sand at the beginning of the experiment.

You will need some sand, some salt, a funnel, a coffee filter, a mason jar or large drinking glass, a pie plate (without pie in it!), a glass measuring cup, a bowl, a teaspoon, and a stirring spoon.


Place 2 teaspoons of salt into the bowl. Add one teaspoon of sand to the salt, but don’t mix it yet. It helps to put salt on one side of the bowl and sand on the other side. Now you will want to taste the salt and the sand. You can spit out the sand when you are finished tasting it. You will have to watch the video at the end of this blog post to find out what my daughter said the sand tasted like.

Look at the salt and sand and feel it with your fingers. Which one is more coarse? Write that down on the chart. What color is the salt? What color is the sand? Are there any other characteristics your kids would like to mention about the salt or the sand?


Write down each of your findings on the chart provided in the book, and then doodle all over the rest of the paper as if you were a mad scientist. Just kidding. You don’t need to doodle.

filtration-doodlesNow mix the salt and the sand together with a spoon. This is called a mixture. Pour 100ml of water into the salt/sand mixture, and stir for 60 seconds until the salt has dissolved.

Place the coffee filter into the funnel, and put the funnel on top of the mason jar. One child can hold the funnel while the other child pours the salt/sand/water mixture into the filter.

filter-experimentThe water will go through the filter, but the sand will be left behind.

Where did the salt go? It disappeared!

Pour the contents of the mason jar into a pie plate, and leave it for a few days. When the water has evaporated, voila! The salt grains re-appear like a magic trick!

evaporated-saltWhat happened? The salt became smaller when water was added to it, and the salt was then able to go through the filter. How sneaky is that?

And the fun thing is that the salt crystals re-appeared larger than what they were at the beginning of the experiment!

salt-crystalsTake a look at the filtration experiment, as we recorded the whole experience on video:

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6 Responses to “#2 Filtration Experiment”

  1. What a fun experiment. I’m sure your kids learned a lot from this.

    • Susan says:

      They did! Who knew that salt could get smaller, go through a filter, and then crystallize larger after the water evaporated? This was fun because it was like magic.

  2. That’s great! We’ve grown salt crystals before, but that really adds a new twist, comparing it to sand and making it “vanish!” 🙂

  3. Ticia says:

    You know, we’ve never grown salt crystals, that would be fun to do.

    Where did you get the lab coats?

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