Water is Super Cool!

Since there has been so much rain, we continue our rain study by using a science kit that we had picked up at a charity shop that is relevant for our purpose.

There are 25 experiments to do with this kit, but not all provide new learning experience for us so we only did those what looked interesting and taught us something new.

1) Density
The first experiment we did was to find out whether all liquids weigh the same.  To do that, we prepared two jars of warm water -- the jar on the left has several tablespoons of salt added to it.

We then gently put each egg into the jar.  The egg in the salt water jar floats because salt water is denser than plain water, so the weight of the egg does not have to push away or displace as much water to make space for itself (compared to the egg in the plain water), therefore it floats.

 

I think this can also be explained by the differences in molecular structures between salt water and plain water, but we will come to that when we learn more of chemistry.  For the moment, the above simple explanation is enough for us.

The next experiment has to do with mixing oil and water.  First, Tiger half filled a glass with cooking oil, then topped it up with plain water.  He observed that the oil found its way up the glass and floated on top of the water.  This is because water is less dense than water.

2) Temperature
We wanted to find out whether salt affects the freezing point of water, so we filled two containers with cold water and added a teaspoon of salt to the one labelled with "S".

 

Both containers were put in the freezer and checked every 15 minutes for their stages of turning into solid.

Ice crystals started forming in the plain water container after 30 minutes, while nothing happened with the salt water in the same duration.  After 90 minutes, the plain water had become solid ice while the salt water was still in liquid form.

3) Supercooled Water
The coolest thing we found out was about supercooling.  The gist of it is to bring water to a temperature below freezing point while maintaining its liquid form, then turn it into frozen ice instantly.  In the natural world, this phenomenom happens in the clouds in the northern hemisphere during winter for rain to form.

It is too cool to miss, so we decided to try it out for ouselves.

Alas, the cool factor eluded us.  We couldn't make the experiment work despite numerous attempts.

Apparently, achieving the desired result isn't so easy after all, according to the clip below.  Phew, that made us feel less incompetent.  The clip also explains what is happening to the molecules during the process:

4) Surface Tension
This is an experiment where we made a cascade of slow flowing water using the attraction of water molecules and surface tension.

We wet a piece of cotton string then tied one end of it to the jug handle.  The jug was filled with water.  The other end of the string was held taut against a small jar.  Tiger then lifted the jug so that the string passed over the spout.  The water was poured gently.  If you look carefully in the clip here, you can see the water flowing along the length of the string into the jar.

The reason for this observation is because the wet string attracts the molecules in the water while the surface tension creates a skin on the outside of the water.


5) Absorbency
The activities we did at home were supplemented with a hands-on workshop at a water treatment centre where the children did additional experiments related to water and recycling.

A simple experiment is to drop a few drops of water onto different types of materials to find out which material is the most absorbent.

The next experiment investigate three factors at once:

1. which type of earthy material (gac, sand, or gravel) is the most effective for filtration;
2. which type of earthy material (gac, sand, or gravel) is the most abosrbent.
3. which type of earthy material (gac, sand, or gravel) is the most permeable.

6) Recycling
As the facility we went to is a part of a water treatment centre, recycling naturally forms part of the education programme that was on offer.

One of the experiments the children did was to find out why they should only put toilet paper (rather than other paper materials) down the toilet.

1. To do this, three pots with plain water were prepared.  A piece of different material (toilet paper, tissue paper, wet wipe) was put into each pot.
2. The pot was then sealed and the children shook each one vigourously for 5 minutes.
3. The children then examined the contents of each pot to see the different degrees of disintegration that has occurred.  We found that the toilet paper broken down the best, followed by tissue paper.  The piece of wet wipe did not break down at all.

The children also had a go at paper making using torn up pieces of waste paper.

This post is linked up to:

1. Entertaining and Educational -1700's Wig
2. Collage Friday - Infinite Value and Learning in Each Moment
3. Weekly Wrap-up: The One Where We Got Back to School
4. Homeschool Mother's Journal {January 18, 2014}
5. Science Sunday: What Do Your Students Needs to Know Before High School Chemistry
6. Hip Homeschool Hop - 1/21/14