Saturday, February 28, 2009

Science Saturday Challenge #5

This week’s challenge is inspired by the Journey North: Mystery Class in which our co-op is participating.

Seasons change because the earth rotates around the sun at a 23.5° angle. Because of that angle, the amount of daylight—photoperiod—changes from day to day, and on any given day it is different based on your latitude.

Here’s an interactive animation about the seasons at Teacher’s Domain (free registration.) Also check out The Reasons for the Seasons by Gail Gibbon or Sunshine Makes the Seasons by Franklyn M. Branley.

This week's challenge involves calculating and plotting photoperiods to demonstrate how they vary throughout the world.


First create or download a photoperiod graph. The X axis is the date and the Y axis is photoperiod (from 0 to 24 hours; see here for an example. Scroll down to the Mystery Class graph.)

Figure out your own longitude and latitude by entering your U.S. town or one nearby into the USNO web site and click “Get Data” or entering your location outside the U.S. at the Getty site.

Find the longitude and latitude of 6 cities north and south of you. Spread these out from north to south as much as possible; it does not matter what longitude they are in. Find two cities east or west along the same latitude as you. You will also need to know the time zones (map here) based on Greenwich Mean Time (GMT.) Note: if you use cities in the US you can just enter the name into the USNO site and get longitude, latitude, and time zone (see below.) For cities outside the US you can use the Getty site or a map.

Use the USNO web site to find the sunrise and sunset data for your home and your chosen cities. If you are using US cities you can simply enter the city name in the top FORM A section. For cities outside the US, use the lower FORM B section by entering in the longitude, latitude, and time zone. Repeat this for several dates; I suggest doing the same day of the week for several weeks before and after the equinox, and then several weeks before and after the solstice.

Calculate the photoperiod (amount of daylight) for your nine locations and plot them on your graph, each in a different color.

Check out the slopes of the lines and consider where these locations are in relation to each other. How does moving east to west affect photoperiod? Can you tell if a location is north or south of you based on the photoperiod? How do photoperiods affect climate? How does the data change around the equinox and the solstice? There's a lot of science and math you can discuss relating to this project.

Wednesday, February 25, 2009

NatGeo's Known Universe

Known Universe premiered this month on the National Geographic Channel. If you missed it, I suggest you find out when it will air again.

It's a three part series: The Biggest and the Smallest, The Fastest, and The Most Explosive. It covers topics like the time-space continuum, the Big Bang, black holes, meterorites, gravity, and much more. It can be intense at times with some discussion of the likelihood of future dooms-day scenarios, but mostly it is filled with lots of great physics and astronomy presented in a clear and engaging program.

Sunday, February 22, 2009

Living Book (and publisher): Little Skink's Tail

Little Skink is a lizard with a brilliant blue tale that falls off to protect her. She then imagines herself with the tail of other forest creatures until she is surprised by finding her own tail has regrown.

The book is geared towards younger children and is a lovely nature story, not just a telling of facts. The illustrations of the five-line skink with various tales are beautiful and amusing. The book even has mapping and matching activities in the back. According to the book flap, this is Janet Halfmann's 28th book so I am very interested in her other writings.

The book is published by Sylvan Dell Publishing, a company dedicated exclusively to math and science literature. Their offerings are mostly on Nature, but with several other topics as well. Still, their nature books alone are well worth adding to your "must read" list for living science. The editor and co-owner homeschooled her children, and they even ran a contest for homeschool student last year. What a perfect Living Science publishing house!

Saturday, February 21, 2009

Science Saturday Challenge #4

We've been learning about properties of matter, and this week's experiment demonstrates a few of them. We read pages 10 - 19 in the Usborne Science Encyclopedia. Search for keyword "properties of matter" at your library for relevant titles.

First you'll need to make a super saturated salt solution (a.k.a. brine) by boiling 2cups of water and then adding salt in batches, stirring in between, until the salt no longer dissolves. Let it cool.


Water (hot and cold)
Food coloring
3 small glass containers


Put equal amounts of brine, ice water, and hot tap water into each of the three containers (we used special plastic test tubes, the ones from which 2L bottles are made, with 2 tablespoons of liquid in each.)

Add a drop of food coloring into each at approximately the same time and watch what happens. In this video, red is hot, yellow/green is cold, and blue is brine.

The red and the yellow/green drops sank at about the same rate, but the red diffused throughout the water much faster. You can see this better with purple dye better (purple is cold, red is hot water.)

Density is mass (g) per volume (ml) or
D = m/v
For a liquid this is easy to calculate. For a solid you can figure out the volume by how much water it displaces (see pg. 17 of the encyclopedia to set this up.)

Other Resources:

Chem1 Virtual Textbook: Density and Buoyancy (advanced)

I Love Density has a complete science project on density (intermediate)

We found several Gizmos that demonstrated density. One had objects on a shelf that you could put on a scale to get weight (mass), then in a graduated cylinder to get volume. I did the calculation for the kids (they were fractions that I converted to a decimal.) You can then put the object in a liquid in which you can adjust the density. The kids were impressed when I started out with the object floating and as soon as I adjusted the fluid density to a number less than the object, the object sank.

Friday, February 20, 2009

Skeleton model

We finished our skeleton model this week, as well as the corresponding chapter in Blood and Guts.

In the picture, the models are being held onto a magnetic bar by magnets embedded into color plastic spheres that I placed in the eye sockets.

My kids also taped their thumbs to their palms and tried to do their daily activities that way. It lasted 30 minutes.

Wednesday, February 18, 2009

Living Media: ExploreLearning Gizmos

offers a one year $149 subscription, or $97 if you buy through Homeschool Buyers Co-op of over 400 math and science simulations called Gizmos. For the price you get an extensive offering of really great math and science simulations.

Gizmos are grouped by subject (math or science) and grade (3 to 5, 6 to 8, and 9 to 12.) Within each subject and grade are topics, like Life Science, Physical Science, Earth and Space Science, and so on (or Number & Operations, Algebra, Geometry, Measurement, and Data Analysis & Probability for math.) Each topic has subtopics, each of which have half a dozen or so Gizmos. They require either Flash or Shockwave players, both of which are free.

While each Gizmo comes with an Exploration Guide and assessment questions, my kids love to just play with the various simulations, even science ones geared toward high school. When done with the guides and assessments, though, the topics are rigorously covered, especially from 6th grade on, making Gizmos well worth using as a spring board for lesson planning.

Gizmos are colorful but not flashy, make sounds but are not noisy. Many are intuitive to use making them great for both formal lessons or fun exploration. The site offers an anonymous 5 minute free pass or you can register for a free 30 day trial.

By the way, read my Living Media post on Science of Relations, my homeschool blog, if you are curious about the label.

Saturday, February 14, 2009

Science Saturday Challenge #3

Expanding and contracting air has myriad applications; in our home lab we'll use it to inflate and deflate a balloon. Adding heat energy to air causes it to expand and displace cooler air, thus decreasing its density and causing it to rise. It follows that cooling the air has the opposite effect.


Plastic soda bottle



Fill the soda bottle with very hot tap water and let it sit for around 5 minutes to warm it up; empty the hot water.

Put the opening of the balloon over the opening of the bottle. Run the bottle, cautiously, under the hot tap water. You will see the balloon inflate a little.

Now run cold tap water over the bottle. The balloon will not only deflate, but may also be pulled into the bottle quite a bit. Run the hot water again to re-inflate the balloon.

Here are three videos demonstrating what happens:

Sometimes this is done by putting burning paper into the bottle, and instead of a balloon you use a hard boiled egg on top of a jar with just the right sized opening, sucking the egg into the jar. But this can mislead some to think that the flame is creating a vacuum by consuming the oxygen (which is replaced by other gases so no vacuum is formed.) And this version can be reversed in both directions repeatedly, making it a hit if you have multiple children that want to try it out.

Here's a PBS interactive demonstration of what is going on.

Wednesday, February 11, 2009

Tuesday, February 10, 2009

Homeschool Showcase

Check out the Homeschool Showcase at Weird, Unsocialized Homeschoolers. Lots of great stuff to inspire you, hosted on an outstanding blog. Enjoy!

Sunday, February 8, 2009


Would you like a chance to look at bugs through a scanning electron microscope? My boys would, and Bugscope gives kids that chance. After signing up ("Home School" is one of the radio button options under "School Information") they will contact you to confirm the 1 hour time slot. Then you send them bugs that you want to view in the SEM.

I signed up our homeschool coop since I am about to teach a Beginner's Microscopy class. I am hoping to schedule the hour for the last Thursday in April, our last day of class. One of the advantages of homeschooling is that we could book the session in the summer if April doesn't work.

I sure hope we thaw here earlier enough to get some interesting bugs to them in time should we get that April date!

Friday, February 6, 2009

Science Saturday Challenge #2

Pressure is force applied over an area, P = F/A. The larger the area, the less the force on each unit of area. In other words, the force is "spread out" across the whole area.


4 balloons
1 small table or other long, flat area that kids can stand on


Inflate the balloons about half way, tie them off, and place them on the floor.

Turn the small table over and place it on the balloons.

Holding the table stady help your children stand in the center of the table.

Ds#1 knew right away that the balloons would not pop, though he thought it had more to do with the balloons not being directly under his weight.

They noticed how the balloons changed shape; I pointed out that all 4 balloons changed because the weight (force) in the center of the table created pressure in all 4 balloons and was, in fact, divided among the balloons. Also, the balloons spread out so that more area touched the table, which decreased the pressure on any one spot.

When you do it, put the balloons under the table a bit more, otherwise the corners of the table can dig into a balloon if a child does not step directly onto the center of the table. Ds#3 stepped up with ds#1 for a total combined weight of about 100 lbs. Ds#2 had a fever and only wanted to look on.

The standard unit of Pressure is 1 pascal (Pa) = 1 Newton/m² = kg/(m· s² ), named after Blaise Pascal, who invented the hydraulic press and the syringe, among other things. The Imperial equivalent is psi, or pounds per square inch.

You can also demonstrate this using straight pins. Tape graph paper to cardboard. Stick a pin through every corner. Place an inflated balloon on the pins and a brick on top of that. Just like the bed-of-nails trick!

For more information visit:

Thursday, February 5, 2009

Google Earth's New Features

Google Earth 5.0 is now available, and continues to be a free download. One neat new feature is ability to explore the ocean. Other features include historical images and virtual tours. Here is an introduction to the new features.

If exploring the earth is not enough, you can explore the surface of Mars as brought to you by Google with the help of NASA imagery. Here is an explanation of how it works.

Monday, February 2, 2009

Really beautiful snowflake pictures

Kenneth Libbrecht is a physicist that studies snowflakes and takes pictures of them with a photomicroscope. The results are stunning! Here is a gallery that displays nine of them.

Snowflakes, The Art of the Snowflake: A Photographic Album, and The Little Book of Snowflakes are a few of his books filled with this beautiful photography, and probably a fact or two about snowflakes.

We're getting more of the lovely crystals tonight.

Hands On Homeschool Blog Carnival--First Edition

I am excited to announce the first edition of the Hands On Homeschool Blog Carnival at Cheryl's blog, Talking to Myself. It has over a dozen entries and over half of them are science related (science naturally lends itself to hands on learning, doesn't it?)

I pray this blog carnival blesses your homeschooling endeavors. If you would like to contribute a hands on project to the next edition, you can do that here.

Sunday, February 1, 2009

Journey North

Journey North is a web site that has a series of programs for schools and homeschoolers to follow along with. Many of them relate to animal migration sitings, thus the name, though it has other projects as well. One relates to whale migration, another to observing seasonal changes throughout the year (starting in September.)

I signed up our homeschool co-op to participate in the Mystery Class. For 10 Mondays we will record our local sunrise and sunset, and calculate our photoperiod (amount of daylight.) On Friday we will look up the same data for the 10 Mystery Classes scattered throughout the world. Later in the program the site will post other geographical clues to these locations. In the end we submit the data, and have an opportunity to talk with the Mystery Classes.

The program begins tomorrow, February 2nd, and I found out about it yesterday. I have seven families so far, and I hope to find 3 more so each family will track one of the 10 Mystery Classes. During the week each family can find their own sources to learn more about daylight around the globe and through the seasons, longitude and latitude, graphing, data collection, and such.

These are simple and fun projects to apply science and math concepts.