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Experiment: Density of Sea Water

Milford Sound

In our study of the ocean, we come to another interesting fact about salt water.

It is more dense than fresh water.  This means that there is more mass in a volume of it than there is in fresh water.  More mass means that gravity has more effect upon it.

Salt water is heavier than fresh.

You can test this in your kitchen lab.

Materials:

  • a transparent container
  • food coloring
  • distilled water
  • salt
  • plastic wrap (may use paper)

Procedure:

  1. Into the glass container, put the water and enough salt so that the water is saturated and there is salt on the bottom of the jar.
  2. Add a few drops of food coloring.  Just for a moment enjoy the sight of the color diffusing into the water.  Stir it up to finish the mixing of the color.
  3. Carefully, place the plastic wrap on the surface of the colored water.
  4. Slowly pour some distilled water onto the plastic wrap.
  5. Slide the plastic wrap out from the jar smoothly so that the two bodies of water do not mix.
  6. Do you notice a clear layer of water standing above the colored water?  If you are careful not to agitate the water, it will remain so for a number of hours.  Gradually, the color will become uniform throughout the jar as the molecules of the salt diffuse throughout.

How does this effect show up in the world?

In Texas’ Galveston Bay, rain (fresh water) falls onto the surface of the water and forms a layer of fresh water on top.

Where a stream meets the Pacific Ocean (or Atlantic) the stream water will tend to stay at the surface of the water until the two are mixed by tidal or wave action.  Milford Sound, in New Zealand, is fed by fresh water streams, and maintains a constant fresh water layer several feet deep above the salt water.

Have you encountered any other examples of this phenomenon in your homeschool adventures?  Leave a comment and tell us about it!

 

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Acceleration Options for the Gifted Child

The education of a gifted child can be interesting because, like all children, gifted children develop in stages and in spurts.  They often are inconsistent in their abilities and may be extremely good in one subject and extremely poor in another.  Your brilliant young mathematician may not be able to spell his sister’s name!

They may develop sudden, intense curiosities for obscure (to us) subjects, like whales.  He reads everything on whales in the encyclopedia, and goes on to contact the Study the Whales Committee to apply for a grant to study the whales.  So, you get geared up for a great unit on whales when, poof, he is interested in airplanes.  And is this the same child that two months ago wanted to build his own computer (starting with the circuit boards)?

But, you say, the texts you bought don’t have anything in them about whales, or computers.  Besides, he doesn’t have time for independent studies because of his regular work that he says is boring.  In fact, even math can be a pain when she already knows how to do the problems in the fifth grade book.

You know that there are probably techniques she doesn’t know (meaning that they have not been explained to her yet), so you are leery of skipping ahead.

Is any of this familiar?

If so, read on for a few ideas about how you can manage when the curriculum doesn’t meet the needs of your child.

Actually, the first task is acknowledging that the curriculum doesn’t measure up.  The reality is that there are children who do not need a lot of practice and who catch on to concepts quickly.  Some children merely need to read the book to assimilate the material.  It is unfair to require that they go lock step through material they already understand.

What can you do?  What can you skip?  How do you know if he is missing something important?

These important questions may have an answer in acceleration, either moderate or radical, and in using such techniques as compacting and prescriptive teaching.

Acceleration has always been the mainstay of gifted education.

One form of acceleration is simply speeding up the pace of the lessons. Although this can be very fulfilling to a student who is a motivated, fast worker, the pace would just bog down many gifted children.  If some of the busy work were simply cut out by compacting and prescriptive teaching, this moderate acceleration is more workable.

Another form of acceleration is called radical acceleration.  Most gifted children can skip entire grade levels in a subject with no ill effect and some should skip entire grades in every subject.  Because most texts are written in the spiral method with concepts re-introduced every year, a child will probably not miss a thing.

Whatever the level of giftedness and acceleration, any child who does not need the practice and who can understand easily and quickly, does not need to go through curriculum at a normal pace.

Acceleration is a good option for gifted homeschoolers.

Compacting means using a regular curriculum but teaching it in less time by eliminating traditional methods.  The Johns Hopkins University at the Center for Talented Youth has pioneered courses in which a whole year of material is compacted into three weeks.  In the American History course (high school level) students do some field trips, a debate, a research paper, several tests, many essays, and a lot of reading as they cover all of American History.

You can do this at home by using the text as a reference book; by often using other ways than tests to evaluate your student’s understanding; and by incorporating a few good ideas like a research project, field trips, and essays.

Obviously, the student would do all this instead of more routine work, not on top of it.

Another way to compact is by using pretests.  Give him or her the chapter test and if your child scores well, then skip that chapter.  Also, in most texts, the first few chapters are reviews of last year’s work that you can certainly skip.  In a more radical move, use a placement test to determine the grade level at which your child should be working and believe it even if it shows that your child should be two grade levels higher.  You can always return to the skipped text(s) if there is a problem.

Prescriptive teaching is similar to the methods already mentioned in that the student skips material he or she already knows.  Find out what he knows by testing, mark the topics he misses and cover only that material. 

Mastering Mathematics sells a comprehensive test over arithmetic skills that can help in this way.

For grammar or language arts, use the final exam from the text to determine any missing concepts, and then teach only those.

If your child is profoundly gifted, even these options may not be enough.  A different type of text may be the best solution; one which is not written in a spiral, but which covers the entire topic once.  As well, you may decide to use a single advanced text instead of many elementary texts.

When homeschooling, you are not bound by a set of rules about how you cover material, but you must first recognize if the curriculum is not meeting the needs of your gifted child.

Then, apply a method of acceleration that is appropriate for your child whether moderate or radical, using compacting, prescriptive teaching, or some other type of acceleration.  In this way you can challenge your child and give him or her the time for wonderful projects and investigations.

What solutions have you found in teaching your advanced student?  What resources are you using?  Leave a comment and let us know about it!

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Experiment: Salt Water and Buoyancy

This experiment serves to illustrate some of the properties of salty water.  As you do this experiment, be sure to record it in your notebook.  Use the scientific method in a writeup of the experiment.

A characteristic of salty water is that in it things float better than they do in fresh water.  In a fresh water lake you would float a little lower than you would in the ocean.  The more salty the water the higher you would float.  You would float higher in the very salty Great Salt Lake than you would in the less salty ocean.

You can demonstrate this in your kitchen.

Materials:

  • Salt
  • Distilled water
  • 2 clear glass containers
  • a wooden block

Procedure:

  1. Place equal amounts of distilled water into the glass containers.
  2. Into one of the glass containers, place four tablespoons of salt.  Mark the container so that you know which one has the salt.
  3. Mark your wooden block with a fine tipped indelible marker so that it is marked vertically into half centimeters.
  4. Place the block into the distilled water carefully so that the block is upright in the water.  You should be able to read the markings on the side of the block to determine the depth at which the block floats.
  5. Repeat using the salty water.
  6. Compare the results.  In which type of water did the block float the highest: salty or distilled?

I tried this with a marshmallow.  The marshmallow in the salty water floated slightly higher than the marshmallow in the distilled water.  But since I had not marked the marshmallow first, the results were hard to see and the marshmallow started to dissolve.

This experiment works well with fresh eggs.  When placed in fresh water, an egg sinks to the bottom of the glass.  When placed in a glass of water with 1 tablespoon of salt dissolved in it, the fresh egg will float.