Sunday, July 24, 2011

The Catholic Laboratory

The Catholic Laboratory is one of my favorite science resources!  The site is the creation of Ian Maxfield, and his podcast is packed with great information.  He has explored Science from a Catholic perspective in regards to the Origins of Life, the Age of Discovery, and the Theology of the Body, among others.  While subscribing to the podcast will get  them to your readers, visiting the page for each topic will get you links to the information presented.  Visit the downloads section for flyers and presentations about Catholicism and Science.  I highly recommend this great resource.

Sunday, July 17, 2011

Charles, Boyle, Divers, and Balloons

If you scuba dive, you know these gentlemen; even paramedics are taught their laws when learning about diving-related emergencies.

They are introduced in chapter 3 of Liquids and Gases: Principles of Fluid Mechanics.  Solids and liquids, in general, are non-compressible; gases, however, are and that changes pressure and density.  Robert Boyle invented the air pump, something with which any child that plays with a ball or rides a bike is familiar.  His law states that the volume of a gas is inversely proportional to its volume, if held at a constant temperature.

Taking what we learned from Archimedes, Pascal, and Boyle, we created something named after Rene Descartes--a Cartesian Diver. The book shows the same principle using an eye dropper, but this example in Gizmos and Gadgets is much more fun, if it is a bit more work.

1 small foil container
1 bendable straw
1 small paperclip
A small amount of modeling clay
2L bottle with a cap filled with water

I used a small foil container to cut out my 3 inch "diver." Next I cut off the bendable portion of the straw, leaving about an inch on either side.

I used the paperclip to attach the straw to the diver by first clipping one side of the straw and then clipping that onto the diver.  I then gave the diver some clay boots to weigh it down a little but not have it sink altogether.  You can see in the picture that when I put it into the water it bobbed at the top; I just pushed it in a little and put the cap on.

Archimedes taught us that objects float by displacing the fluid they are in, so that the object is less dense than the fluid.  Pascal taught us that water exerts pressure in all directions and is basically non-compressible. Boyle taught us that gases are compressed, and that compressing them increase the pressure and the density.  Our diver has a straw tank of air and is surrounded by water.  What happens when you squeeze the bottle?

The chapter wraps up discussing the effect of temperature on gases. Jacques-Alexandre-Cesar Charles, while ballooning, noticed that hot air expands, but the law named after him was first stated by two other great scientists, John Dalton and Joseph-Louis Gay-Lussac. Charles law states that for a constant volume of gas, the pressure of the gas is directly proportional to the temperature. While I did this with the group, I also did it awhile back with my boys and the videos came out better:

ExploreLearning has  two Gizmos to reinforce these concepts: Temperature and Particle Motion and Boyle's Law and Charles' Law

Friday, July 15, 2011

Pascal and Liquid Pressure

Chapter 2 of Liquids and Gasses has lots of fun water experiments.  Because the weather was not conducive to being in it, we used the bathtub.  We punched holes in a milk jug and watched the water shoot out father from the bottom hole than the top hole.  We also poked a hole in the bottom of one cup and the side of another to demonstrate that pressure is in all directions.  I thought this would be rather simplistic, but I underestimated boys' fascination with water.

The rest of the chapter we discussed.  The illustrations in the text are great, but I wanted to find or rig a container similar to what is pictured in the book with the connected water columns and the piston.  They got a basic understanding of the concept but I extended it to remind them that what they gain in strength they have to make up in distance, just like other simple machines.  A simulation or demonstration would have gone a long way here.

They really liked the tie in to hydraulics, amazed that this simple concept is used to create the brakes of a car.

They so enjoyed fluid mechanics that the following week one of the boys brought in a hydraulics kit that they spent the class exploring.  Something about boys and water...