Experiment 6.1 Earth and the Lithosphere

MODULE #6: Earth and the Lithosphere
EXPERIMENT 6.2
A Simulation of Plastic Rock

I. Purpose

Plastic rock flows like a thick liquid and then solidifies when subjected to an abrupt force. In this experiment, you will produce a mixture that simulates such behavior.

II. Equipment

• A shallow pan (a pie pan, for example)
• Cornstarch
• Measuring cups
• Water¨Spoon for stirring
• Eye protection such as goggles or safety glasses
  

III. Procedure

1. Put one cup of cornstarch into the pan.
   
2. Add two-thirds of a cup of water.
   
3. Stir the water and cornstarch together. You should find it very hard to stir at first, but as you continue to stir, you should get to the point where you have an evenly mixed, white liquid in the pan.
   
4. Add ½ cup of cornstarch to the mixture.
   
5. Stir the newly added cornstarch into the mixture. Now you should start seeing an interesting behavior. As you stir, the mixture should solidify, making it hard to stir. However, when you stop stirring and let the mixture sit, it should liquefy again. If you don't see that behavior, your mixture is not correct. If the mixture stays liquid, you have too much water. To fix this, add cornstarch a little at a time until you get the desired behavior. If the mixture never turns to liquid, you have too much cornstarch. Add water a little at a time until you get the desired behavior.
   
6. Explore this interesting behavior for a while.
   
7. Pick up some of the mixture with your hand. As you pick it up, it should become solid.
   
8. Squeeze the solid into a ball, then relax your hand and watch what happens to the ball.
   
9. Repeat this a few times.
   
10. To clean up everything, you will need to use hot water from the tap. As you add hot water to the pan, the mixture will become a liquid and pour down the drain. Make sure to leave the hot water running for a while after the mixture has been cleaned up, as you need to flush it down the drain.
    

IV. Data and Observations

1. We poured the cornstarch into the water and the cornstarch filled the air. It smelled, tasted terrible and powdery.
   
2. The water was added easily added to the water. The mixture was very thin.
   
3. While adding the extra cornstarch the pan kept slipping away as we tried to hold it steady as we whisked it. I kept slipping away as it became tougher to stir it.
   
4. After mixing the added cornstarch we stuck our hands into the mixture and slid them around.
   
5. While in the mixture we tried to roll the mixture in ball and it became dry. If we relaxed them the mixture slowly poured out of our hands.
   
6. While cleaning up we added water little by little until it became a thin liquid again.
   

V. Conclusions

I conclude that the behavior of the mixture we made is close to plastic rock. When shaken abruptly or moved quickly the mixture solidifies. However, when the mixture was left alone it flowed like a thick liquid. Plastic rock has similar properties.
Plastic Rock will solidify if moved with abrupt force if undisturbed it will flow like a thick liquid. Scientists are not completely sure why the mixture has such an odd behavior. One explanation says that water lubricates the molecules as they rub up against each other allowing them to flow like a thick liquid. However, if you disturb the liquid by squeezing it or shaking it makes it much harder for them to move. Because it can not move very it also can not flow very well ether so it become more like a solid. The Second possible explanation is that the cornstarches long molecules can flow easily when allowed to do so slowly. When you disturb them, they tangle up with one another making it much hard for them to move. Because it is hard for it to move, it behaves like a solid.

VI. Bibliography

Wile, Dr. Jay L. Exploring Creation with Physical Science. Anderson, IN: Apologia Educational Ministries, 2007