A Simulation of Plastic Rock

Plastic Rock is a rock that behaves like something between a liquid and a solid.  Scientists believe that the earth's mantle has this type of rock flowing through its asthenosphere. 

A simple experiment using water and corn starch will simulate the properties of Plastic Rock.  Follow these simple steps and enjoy your experiment!

1)  Put one cup of cornstarch into a shallow pan (pie plate works well).

2)  Add 2/3 cup of water.

3)  Stir until you have an evenly mixed, white liquid. (it should be hard to stir in the beginning)

4)  Add another 1/2 cup cornstarch to the mixture.

5)  As you stir the mixture, you should begin to see some interesting properties.  As you stir, the mixture should solidify, making it more difficult to mix.  However, when you stop, the mixture should liquify again.

6)  Play with this mixture!  Pick some up and squeeze it in your hand... it should harden.  Open your hand and see what happens!

7)  When you are done having fun - we played with it for about 30 minutes- clean up with hot water.

Plastic Rock is slowly liquifying from hand above to below.

8)  The excited students writing up their Laboratory Reports!

Note: if you don't see this behavior, your mixture may be incorrect.  If it remains liquidy, add more cornstarch; if it is too hard, add water a little at a time until you get the desired consistency.

Happy home schooling!

  Ellen

Water's Cohesion

Let's start with the definition of cohesion.  Cohesion is "the phenomenon that occurs when individual molecules are so strongly attracted to each other that they tend to stay together, even when exposed to tension."  Per Apologia's Exploring Creation with Physical Science, "water molecules are attracted to one another by hydrogen bonds as well as the electrical charges that are the result of polarity.  Because they are attracted to one another, they do not like to be pulled apart.

To visually see this, we performed two (2) experiments. 

1)  Supplies needed: small metal paper clips, bowl of water, small piece of toilet paper, and dish soap. 

 First, we filled a bowl with water.  Then, we cut a piece a toilet paper about 2 inches longer and wider than our small metal paper clip.  Set the paper clip on the paper and place it gently on the surface of the water.  After the paper drops to the bottom, the paper clip should be floating.

The cohesion of the water molecules allows the water strider to "walk" on water!  Since the water molecules want to stay close together, it forms a 'skin' on the water, called surface tension.

Now, let's see what happens when you break the hydrogen bonds.  Add 1-2 drops of liquid dish soap to the bowl of water.  What happens?  The bonds are broken and the paper clip drops to the bottom of the bowl.

2)  Supplies needed: a clean penny, water dropper, and water.

This is a simple experiment but also shows how strong the bonds in water molecules are.  Rinse the penny in water and place on a flat surface.  Fill a small glass with water and fill the eye dropper with water.  Now, drop the water onto the penny one drop at a time.  Count how many drops your penny can hold.  We were able to get to 33-40 drops before the water spilled over the side.

If you look closely, you can see the 'bubble' over the penny.  How many drops does your penny hold?

Plastic Rock... can it be!

Science experiments… Yippee!  Plastic rock flows like a thick liquid and then solidifies when you squeeze it or subject it to an abrupt force.  Put 1 cup cornstarch in a pan and add 2/3 cup water; stir until evenly mixed.  Next add ½ cup more cornstarch.  As you mix it, it should solidify.  Leave it alone, it should liquefy again.  Put some in your hand… squeeze – solid, cup your hand – liquid. 

The above experiment is from the Physical Science book (ed. 2) p. 136-137.

More on this experiment in a few weeks.....

The Chemical Composition of Water

Separating water into Hydrogen and Oxygen gas

Exploring Creation with Physical Science
Experiment 4.1    Apologia

Our experiment today used a 9-volt battery, salt water made with Epson salt, a glass, 2 test tubes, and safety glasses.  By using the battery, we were breaking the water molecule down to hydrogen gas and oxygen gas.

First, we made the salt water and submerged the battery for ten minutes, terminals up, to remove the trapped air from the battery.



Next, we used a large mixing bowl to make more of the salt solution.  We then filled the test tubes completely with the solution.  After carefully moving the filled test tubes to the glass with the battery, we simultaneously placed them upside down over the battery's terminals.  We made sure we had no air in the tubes by keeping the tips immersed in the salt water.

Once the test tubes were collecting the Oxygen and Hydrogen, we monitored the experiment to see how much of each gas was produced.

We learned that the negative terminal battery produced hydrogen gas while the positive terminal collected Oxygen. (Hydrogen is on the left!)  There was twice as much Hydrogen as Oxygen. With our simple experiment, we were able to "see" the chemical formula for water - H(2)O.

Each experiment requires a written laboratory report.  Michael is working on his for this lab!

I Love Science!

Add a link to your blog highlighting your science adventures.  A link back here is nice but not required.  If you don't have a blog, leave a comment.  I am looking forward to hearing about your experiments -- the ones that worked and the ones that.. oh, didn't!