Saturday Science Challenge #13

Layers of the Earth

The earth has 3 basic layers--the crust, the mantle, and the core. Texts will emphasize the thinness of the crust. Making models is a wonderful way to demonstrate this, though I found my kids were particularly impressed by this demonstration.

The earth is not perfectly spherical, and the crust of the earth is irregular, so exact numbers are not really possible, but these are the ones we can use for this activity:

Radius = 6378 km
Distance to core edge = 2890 km
Distance to mantle edge = 35 km (from Wikipedia)

Take a measuring tape at least 6 m long; have someone hold it in place at the "center" of the "earth." First measure out to 2.73 m. Holding chalk and the edge of the tape together, draw a circle, or at least an arc; this first line is the edge of the core. Now bring the tape out to 6m and draw a second arc; this second line is the edge of the mantle. Ask your kids, "How thick is the crust in this model? How much longer do I extend the measuring tape to draw the crust?" Have them mark where they think the line would fall.

Answer: 3 cm

For advanced students, have them calculate the ratios. I choose to have the edge of the mantle to be 6 m, so how large is the full radius for the model? The actual distance from the center of the earth to the mantle's outer edge edge is 6378 km - 35 km = 6343 km. Now set up a ratio:

distance to outer mantle (6346) is to earth's radius (6378) as model distance to outer mantle (6 m) is to model radius (rm).

6346/6378 = 6/rm --> (6378)(6) = (6346)(rm) --> (6378)(6)/6346 = rm
rm = 6.03

You can set up a similar ratio to check the edge of the core.

Saturday Science Challenge #12

Basic Rock Identification

Around here we rarely find rocks made of a single mineral that we can identify through color, luster, streak, hardness, and cleavage, but you can classify rocks into their three basic classes: igneous, metamorphic, and sedimentary.

All you need is one hammer and goggles for everyone participating. A geologist's pick hammer is most effective though this can be done with other hammers. And you need to find a flat, hard surface on which to do the cracking.

You can play the Rock Type Game at Geology For Kids as a warm up. You can also read the classic A First Look At Rocks by Millicent Selsam, or DK e.Guides Rocks and Minerals to get an idea what to look for when classifying them.

Cracking them open, as well as wetting them, really helps to see crystals and layering. And I didn't have to ask twice if anyone wanted to do this activity. For older kids, have them try to identify the specific types in each category. They can also map the location of their rocks, and see if different locations have different predominant types. The Moh's hardness scale is helpful for this, especially the hardness of common items you can use to test your samples.




These two rocks are the same specimen. The picture doesn't show how much more lustrous the inner rock is compared to the worn outer surface.







It's granite, an igneous rock.

Bedrock Samples

Whether it's Nature Study or Geology, it's great having an environmental engineer for an aunt (my sister-in-law.) Not only does she know all the plants in the area, she gives you gifts like pike hammers and bedrock samples. These arrived today. She included an informational sheet as well as a pamphlet about Rhode Island bedrock, complete with a geological map!

These bedrock core samples are the metamorphic rock gneiss formed from granite, distinguishable by its distinct banding. It contains quartz (clear to gray), biotite (black banding), and feldspar (pink.) Some samples may contain flecks of pyrite (Fool's gold.)

The samples are best viewed wet. Why? Think of clear plastic wrap--when you crinkle it, it becomes white because the light is reflected by the countless surfaces it now has. The uneven rock surface (even though these are pretty smooth from the drill) is "smoothed out" by water and so the colors are more intense. This is similar to polishing rocks.

All of these pieces come from the same core sample beginning at about 40 feet deep. Each piece is marked with the depth at which that piece started. The breaks come from pockets of ground water. You can clearly see how the stone changes with depth. Yoou can't tell in these pictures but the deeper stone clearly contains a lot more feldspar than the more superficial stone, which has more biotite banding.

AtHomeScience Yahoo Group

Click to join AtHomeScience

Finally, I have activated the Yahoo Group that I created back when I created this blog. I've added a button to the sidebar if you would like to join. Here is the description:

Everyone is welcome! This group has many Catholic members, including the moderator; as a result, please keep the following in mind:

Please no discussions about "young earth" or "Creationism" and please note if a resource has that perspective. I greatly appreciate families of faith with this perspective; however, information about these resources are available elsewhere, and discussions on this topic tend to get extensive and are without resolution.

Many wonderful secular resources will be discussed, and most of them have no reference to Christianity. Those that do will be discussed in light of their view on Christianity. On some occasions, discussions about Science and Catholicism will take place as well. Any anti-Catholic comments will no be posted.

May this list be a blessing to your own science homeschooling journey!

Geology Study Resources

We are taking up earth science at our house this year, and we are exploring it with our small co-op (3 families, 11 children under age 11, 8 of which are school-aged) We have had a lot of fun so far investigating geology, so I thought I would share some of my resources.

I am using Be Your Own Rock & Mineral Expert by Michele Pinet as our spine. This thin hardcover works well to outline lessons, including activities. It is particularly good at describing techniques and making tools for rock hunting, and then for testing samples. You will need other sources for specific identification. Unfortunately this book is out-of-print and quite expensive; my copy is from our library. This is actually geared to high school kids but it is easy enough to adapt.

I have found several wonderful living science books, most of them written 20 or more years ago. Many of these, however, are still in print and some have even been updated! In fact, the only two on this page that are out of print are the books by Pinet and Selsam.

Some of these are strictly about rocks and minerals while some relate to the rock cycle or the earth's composition. I find it helps kids understand and distinguish igneous, sedimentary, and metamorphic rocks. One of our family's favorite authors is Milliscent Selsam, and A First Look At Rocks is no exception. The black and white pictures have obvious limitations, but the writing is just spectacular juvenile science. The book is a great introduction to the three types of rocks and the characteristics of each, so you can go out and start classifying your finds. Her books, unfortunately, are out of print but they are readily available on the used book market. Another favorite of ours are books from the Let's Read and Find Out series; two of them relate to our geology study.

As for actual pictorial identification, rock and mineral books are plentiful on library shelves. We happen to like the Basher Science books because they are so whimsical, the information is in bite-sized pieces, and my kids love to look at them, and the newest addition is Rocks and Minerals: A Gem of a Read.

We have subscriptions to Discovery Streaming, which has many related videos, though I liked the ones from United Streaming that I could link to for free from this neat site about the rock cycle called Rocks to Soil.

We also use Explore Learning, which has some great Gizmos. The Rock Classification Gizmo and the Rock Cycle Gizmo and the Mineral Identification Gizmo all fit right into our study. You can try them for 5 minutes at a time for free each time you visit the site, and Homeschool Buyer's Co-op is currently offering a group buy.

Our little class is about to move on to collecting and testing sample. I even bough a small amount of HCl from Home Science Tools for when we get to mineral identification. I hope the weather doesn't get too cold yet!

UPDATE

How could I forget these three wonderful books (thanks Jennifer!):

Solubility, Capillary Action, Math, and Art

This week we had a combined art and science project, with a little math thrown in for good measure!

You need a white T-shirt, permanent markers, isopropyl alcohol (we used 70% though 90% would be fine too,) a dropper bottle (we used a non-medical syringe,) a large plastic cup, and a rubber band. Here you see the boys posing with their new T-shirts ready to start the project.


Slip the plastic cup inside the T-shirt so the opening of the cup faces towards the front panel of the shirt. On the outside of the shirt, pull the shirt tightly over the cup and put the rubber band around the top to secure it.

Put spots of various colors on the section of the shirt secured to the cup. You can put wavy lines, too, if you like the effect.

Here's the science part. Permanent markers are not soluble in water, but they are in alcohol. Fill your dropper bottle with the isopropyl alcohol and drop in onto the decorated section. Because the permanent marker is alcohol-soluble, the ink "runs." Capillary action moves the ink along the fabric.

Because the syringes are graduated, the boys made up math problems as they went along, like, "Mom, if I had 30 mm of alcohol to start and now I have 10 mm, how much did I use?"


Here are the boys modeling their finished projects.

We did have a PROBLEM though. I rinsed the shirts in water before washing them, but all the ink washed away. Next time I am going to rinse them well again, then run them through the dryer to evaporate off all the alcohol (it is very volatile, which is why it has such a strong odor) before washing it. The boys have been bugging me to get more shirts ever since.

One Lovely Blog Award

Thank you Sara in the Woods for this award posted on her blog The Forest Room. Just the graphic alone makes this a neat meme to pass along! I am a tea drinker; I have an entire cabinet filled with different varieties and accessories, with more loose teas in my ginger jars.

Here are the rules of this award:

Accept the award, post it on your blog together with the name of the person who has granted the award, and his or her blog link.

Pass the award to up to 15 other blogs that you’ve newly discovered. Remember to contact the bloggers to let them know they have been chosen for this award.

1. This needs to go back to Sara and The Forest Room as her blog is a wonderful discovery!
2. Learners At Home are from my neck of the woods...
3. ...as is Every Day Best (and a long lost college friend!)
4. Live Life with Your Kids is another neat CMer blog.
   
5. Over the summer I found Catholic Cuisine and we are actually going to incorporate it into our TORCH classes this fall. They have the lovely tea set up in the corner, too.
   
6. Heart of a Mother is another lovely and inspiring blog new to me.

I could also give this to most of my long time favorites, too!