Monday, July 31, 2017

The Magic Paper Towel: Exploring Water Repellent





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Back to school time is here with the TeachersPayTeachers.com sale. 

All items in my store are on sale.

Science demonstrations are a great way to wow your students the first week of school. 
Here is a fun one to spark their interest!

The Magic Paper Towel
We all know paper likes to absorb water. 
What if we make paper towel water repellent?
Watch the video to find out how to create water repellent paper towel!

1.   Place a piece of regular paper towel at each group.
2. Pour about 250ml of water slowly on each group’s regular paper towel.  Try to keep it on the paper towel.  Students will notice it absorbs the water and some most likely spreads.
3. Have students clean up their area.
4. Place a piece of water proof paper towel at each group.
5. Pour about 250ml of water slowly on each group’s water proof paper towel.  Try to keep it on the paper towel.  Students will be amazed to notice the water does not soak in.  It stays on top.  Even the bottom does not get wet.
6. Have the groups discuss what happened.  They need to try and figure out how the teacher did this.
7.  Then show them the water proof spray.
8. Have extra water proof paper towels to give students an opportunity to explore.

Why is this possible?


The paper towel was sprayed with silicone based water repellent.  Silicone is a hydrophobic substance.  That means it does not absorb water.  Paper towel is naturally hydrophilic (water loving).  Which means it absorbs water.  The water repellent creates a barrier keeping the water out.  Water forms curved drops on the paper towel because it has polar bonds.  Water molecules have a positive and negative end.  This means water molecules are attracted to each other.  The drops attract to each other forming raised droplets on the water proof paper towel.   This attraction creates surface tension.

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