Friday, February 18, 2011

Outdoor Hour Challenge - Winter Series #6 - Salt

We've been enjoying doing the nature studies and challenges on the Handbook of Nature Study website, so I decided to do another one this week.  This one is the Outdoor Hour Challenge Winter Series #6 - Salt.

The website says, "For this challenge we will be doing something a little different. How would you like to grow your very own crystals to observe? You can make our own crystals by dissolving salt in water and then letting it sit in a saucer in your very own windowsill." 

This description immediately was of interest to the girls.  Did they want to make crystals?  Yes!

The sentences below that are in bold typeface are from the Handbook of Nature Study website.  The sentences in regular typeface are my comments.  When I've used quotes from the Handbook of Nature Study (HNS), I put those in italics.

Inside Preparation Work:

Read pages 753-754 in the Handbook of Nature Study. These pages give you a quick study of this common substance that we use daily.

Each [salt] crystal is a beautiful little cube, often with a pyramid-shaped depression in each face or side.

Close-up of salt crystals.  This image is from the internet.
Hopefully, the ones the girls make turn out like these.

In Ithaca, New York, the salt deposits are about 2,000 feet below the surface of the earth.

When the United States was first settled, salt was brought over from England; but this was so expensive that people could not afford it, and so they soon began to make their own salt by evaporating sea water in kettles on the beach.


I read a few books to the girls:

The Story of Salt by Mark Kurlansky

The Story of Salt is a kid-friendly version of Salt: A World History. In it, Kurlansky shares the history and science of salt. Here are some interesting things we learned while reading this book:
•Salt is the only rock consumed by humans.

•Salt paid for the Great Wall of China.

•Roman soldiers were often paid in salt.
•Without salt there would be no mummies.

•When the Jamestown colony was started, a saltwork was established.

•When America declared independence from England, the salt supply was cut off. (Salt was needed to make gunpowder. Losing their supply of salt prior to a war was a major challenge.)

•Ghandi walked 240 miles to the sea to defy British law and make salt.

•Today, the U.S. is the world’s largest supplier of salt.

The second book that we read was Sodium by Savatore Tocci. This book wasn't as interesting as the first book, but it did have some interesting facts - especially how sodium affects the human body (both positive and negative).

The third book that I used with this nature study was Welcome to the U.S.A. - Utah by Ann Heinrichs.  There are two pages about The Great Salt Lake.  When I read the part about being able to float in the Great Salt Lake, I could refer to the floating egg experiment that we did earlier in the afternoon.  This helped the girls immediately visualize the salt water and the abililty for someone to float in the lake. 

One thing we learned was that the northern part of the lake is saltier than the southern part.  Also, if it rains the saltiness of the water decreases, so things cannot float as easily in the lake.


Be sure to read through the lesson starting on page 753 that outlines an easy to complete activity to make salt crystals to observe using regular table salt and water. Get your crystals growing and then take your outdoor time. I would suggest putting the saucer in a warm windowsill where it will not be moved.

There were some questions in the HNS that encourage children to observe.  The questions are in italics below, with the observations made by the girls in standard typeface.

When you pour the salt into the water, what becomes of it?  The water gets absorbed by the salt.  It gets thick.

How do you know when the water will hold no more salt? The water is gone and only wet, thick salt is left.

In a few days, the girls will be able to answer the following questions:

After a bowl filled with the salt water has stood exposed to the air for several days, what becomes of the water?

From which saucers did the water evaporate fastest - those in the warm places or those in the cold?  In which did the crystals form first?

Which saucers contained the largest crystals - those from which the water evaporated first, or those from which it evaporated more slowly?

Could you see how the crystals began?  What is the shape of the perfect salt crystal?  Do the smallest crystals have the same shape as the largest ones?


Outdoor Hour Time:

Spend 15-20 minutes outdoors this week in your own backyard carefully looking for something that interests you. Relaxed nature study outside your own backyard can be surprisingly fun since you let your children lead your adventure.

The girls in the tree by Bailey (the pony).

They spent quite a bit of time in the tree despite a drop in temperature (it was only in the 20s today - a drop from near 50 degrees yesterday).

The girls climbing a tree on the nature walk.

We walked over to the tree we were looking at last week (the one with the holes that the woodpeckers made).  The girls found these unusual growths or fungi growing on the bark:

Olivia learned about fungi this week as part of her science lessons, so I took this growth from the tree as well as a couple other ones so the girls and I can draw them, cut them open, and explore them more closely with a magnifying glass.

Another growth higher on the tree.

This mushroom was near the base of the tree.  It looked like it would be easy to get off the tree, but it was actually quite difficult. It was either frozen or just very solid (not soft like a mushroom); and I had to use my foot to press down on it in order to get it off the tree.

Took this mushroom off the tree to explore indoors.

We walked from the east pasture to the backyard where there is a brush pile/fire pit and a double-grafted apple tree.  Half of the apple tree toppled over during the big November 2010 ice- and snowstorm.  The branches that were trimmed were brought to the brush pile where the rabbits have been using it for shelter and for food.

Branches that have the bark eaten off by rabbits.
(Rabbit pellets/waste are on the snow.)

The girls were excited that they could see the little teeth marks left by the rabbits in the wood.

Rabbit teeth marks in the wood.

So, after a brief nature walk, it looks like we'll be further exploring fungi/mushrooms and rabbits during the upcoming week.


Something you might like to try if you have freezing temperatures in your area is to conduct an experiment where you try to freeze salt water outdoors in your own backyard. Take two pie pans. Fill one with tap water and one with salt water. Compare the time it takes for each to freeze.

Pie pans - one with no salt and the other with 1 tablespoon of salt.

The girls and I started at 2:30 p.m. by placing 1 cup of water in each pie pan.  In one of the pie pans, Olivia added 1 tablespoon of salt.  We placed the pie pans outside on a tray in the shade behind some bales of alfalfa. 

The pie pan with no salt froze first.

By 3:56 p.m., the water with no salt had frozen solid.  The water with salt had sections that had ice on top, but liquid underneath.  When the pie pan was lifted, the water underneath moved and spilled a bit onto the tray.

The pie pan with salt was partially frozen, but still had
quite a bit of liquid underneath the frozen top.

What I enjoyed seeing was that when we went out to feed the horses and clean the barn, the girls immediately rushed over to see if the water froze.  They obseved what they saw and were genuinely excited about the results.

Sophia checking to see if the ice is solid in the no-salt pie pan (it is).
The salt water combination in the other pie pan is not frozen.


Follow-Up Activity:

Keep close watch on your salt crystals growing in your saucer. Use a page in your nature journal to record your crystal’s growth. You can use a hand lens to observe the crystal's shapes more closely and then record their appearance in your nature journal.

It took about six days before we actually began to see some salt crystals form in our saucer. They are fairly small but with a magnifying glass we could see their shapes easily. We found it easier to observe the crystals if you put them on a dark surface.

I will come back to this posting to update what the girls observe and to share pictures of the salt crystals. 

This wasn't on the Handbook of Nature Study website, but I thought it might be interesting for the girls to try.  It's called "The Floating Egg" and it was on the Steve Spangler Science website.

According to the website, the experiment is " simple and amazing. A raw egg will float in very salty water but will sink in plain tap water. Why? Salt water is more dense than regular water." 

The first step is to make a very saturated salt solution by dissolving roughly 4 tablespoons of salt in about 2 cups of water. Use pickling or Kosher salt to make a clear salt solution. (We used pickling salt.) Table salt may be used, but the solution will be somewhat cloudy due to the additives used to make the salt free-flowing.

Sophia placing the egg in the
mixture of tap water and salt water.

Fill a glass half full with the salt water. Slowly add plain water by pouring it down the sides of the glass, being careful not to mix the two liquids. Gently drop the egg into the water and watch as it sinks through the plain water, only to abruptly stop when it hits the salt water. The egg floats on the top layer of the salt water.

The egg is floating in the middle of the jar.
When it was placed in the jar of water, it sank
until it reached the salt water.

The next experiment was called "The Rising Egg."  Fill the bottom 1/5 of a tall glass with salt. Add just enough water to make a wet salt layer. Carefully lower an egg down on top of the wet layer of salt.

Olivia placing the egg on the wet layer of salt.

Slowly add more water by pouring it down the sides of the glass so as not to disturb the bottom layer of water. Cover the top of the glass with cellophane and a rubber band. Notice how the egg rests on the layer of undissolved salt on the bottom of the glass.

Be sure to put the glass in a place where no one will be able to disturb it. Observe for weeks. That's right, weeks. Months even! Over the course of the next several weeks, the bottom layer of salt will begin to dissolve in the water above it. As the salt dissolves, the egg will rise off the bottom and float on the layer of salt water.

As more time passes, the salt level continues to drop and the egg continues to rise. Be sure to put the glass in a place where no one will be able to disturb it. Record the egg's progress by marking on the outside of the glass using a felt tip marker.

(Note: We put the egg on the salt on Friday, February 18, 2011. After filling the jar with water and then placing the saran wrap and rubber band around the top, we placed it in the dining room on a high shelf - away from the cats.)


Ice cubes with salt on them (left) and ice cubes without salt (right).

Another experiment we did was called "Which Melts First?"  The girls took two different small bowls each.  In each bowl, they put two ice cubes.  On top of one of each girl's ice cubes, they put 1 tablespoon of salt.  In the other bowl, the ice cubes did not have any salt.  They both anticipated that the ice cubes with salt would melt first.  

41 minutes later.

We started at 2:30 p.m. by 3:11 when the first picture was taken, the majority of the ice cubes had melted in the bowls with ice.

The winner:  ice cubes with salt on them. 

After 3:51, the girls observed that the ice with salt poured on it melted first.  The bowls with no salt still had some of the ice cubes remaining.  The bowls that had salt over the ice cubes were filled with water and the salt had sunk to the bottom of the bowl.


We enjoyed doing quite a few experiments using salt.  The favorite one for us all was the floating egg. 


Kala said...

I really liked Kurlansky's Salt: A World History. It was interesting to hear how something I buy for 50 cents a pound used to be an important trade item around the world.

It sounds like the experiments were really fun.


Very Verdant said...

This sounds like a fun and informative web site. I need to go check it out.

You all did a great job with your lessons!

Anonymous said...

My kids and I stopped by the Great Salt Lake a few years ago, and my son hopped in to check out how much he'd float. He tried to hold his feet down under the water, but they'd just pop back up again.

Barb-Harmony Art Mom said...

Wow! What a great salt study you had and I also enjoyed reading about your outdoor time too! I loved that the salt study was partly done outdoors so it gets you to spend time outside even though it is really cold in your world. I enjoyed seeing your rabbit shelter and the teeth marks too.

I can't tell you how much I am enjoying your entries in this series of challenges. Your family is such a great example to all of us.

Thanks for sharing your link with the OHC. I feel honored.

Monica said...

What a great study! My girls love climbing in the trees too!

Cathy said...

Wonderful study, thank-you for sharing. My kids have been talking about salt lately. I think they would enjoy this study.

I found your post from the ABC's of Homeschooling link-up and I'm now following your blog.