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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.

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Experiment: Salt and Solubilities

“It is an everlasting covenant of salt before the Lord for both you and your offspring.”  Numbers 18:19

The presence of salt in the ocean has always been very interesting to ocean goers, especially since there seems to be no reason why the sea should be salty and not alkaline, or full of some other set of chemicals.  But the reality of it is that the salt in the ocean effects the physical characteristics as well as the chemical characteristics of the ocean and its life.

This experiment serves to illustrate some of the properties of salty water.  As you do the experiment, be sure to record it in your notebook.  Use the scientific method.  If you like, a report can be made using the critical thinking questions included in the procedure.

Salt and Solubilities

One of the basic reasons for a salty sea is the fact that sodium chloride is able to be dissolved in water.  But that saltiness depends upon the temperature of the water.   When water is cold less salt will dissolve in it.  When water is hot, more salt will dissolve.  The Gulf of Mexico is of higher salinity water than is the Arctic Ocean.  The Gulf of Mexico has a higher temperature than does arctic water.

You can test the solubility of salt in water in your kitchen.

Materials:

  • Salt
  • Distilled water
  • Thermometer (for older students)
  • Canning jars
  • Heat source
  • Measuring spoons

Procedure:

  1. Make ice cubes from the distilled water.
  2. Fill three canning jars with water: one with water at room temperature, another with water which has ice in it, and the last with boiling water.  Older students should use more jars with more different temperatures of water in them.
  3. Add salt by teaspoon to each of the jars, stirring between each teaspoonful until dissolved.   Count the teaspoons.  Stop adding salt when it no longer dissolves.
  4. Which jar of water dissolved the most salt?   Explain how the increase in energy of the water molecules affected the dissolution process?
  5. Make a graph showing the relation of water temperature to the amount of salt dissolved in the water.
  6. Does the salt precipitate out when the hot water cools?
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Studying the Ocean

The Sea. Even the name has some kind of elemental drawing power.  People have always been impressed by its size and power.  Boats and trading routes have been important to people since early times.    But, how can you study the ocean when you are landlocked?  How can homeschoolers in Ohio study the sea?  Does Galveston hold all the keys to the study of the gulf or can you take a trip to the ocean at home?

In the United States and, perhaps, in other parts of the world, the oceans are under siege.  Life in the sea has always been in jeopardy from natural events, but today we have additional manmade problems.

Some oceanic problems are: the quality of the beaches, the number and amount of fishes available for catching, and the presence and diversity of life in the upper reaches of the seas.

These three problems are suitable for study for homeschoolers because they are concrete, real problems which can be studied from long distance, if necessary.  The first can even become an action project, too, especially since there are so many lakes and water fronts across the United States.  The problems suggested also present complex legal issues which are excellent starting points for discussing our complicated life as Christians living in a republic.

The quality of the beaches may have changed since your grandparents were growing up….

If you have access to a beach you may decide to conduct interviews in an attempt to document any changes the beach may have undergone whether good or bad.

Young people of thirty or less may not be able to remember the state of the beach in the 1950’s, so you will have to interview some older people to add the perspective of years.  Try to get copies of pictures if you can.  By the way, this activity can be done at any beach, oceanic or freshwater.

Changes to look for:

  1. Presence of private homes on the beach itself.
  2. Presence or absence of garbage on the beach.  What types of trash are found?
  3. Beach closed or open to auto traffic
  4. Distance to shore for fishing trawlers changed.
  5. Has the average size of fish changed in the last two decades?
  6. Addition of groins out into the water to help build up the beach.  (Or allowing them to fall into disrepair or removed totally)
  7. Condition of the substrate (sand ) under the water just off shore has changed.  Is it mostly sand or is it silty?
  8. What are the dangers of the beach to children?  Example:  In the 1950’s, children were warned to only go in the water ankle deep while beachcombing alone and to avoid stepping on man-o-wars.  Now, children should not even go alone and when beachcombing they should be wearing shoes because of the new hazards of the beach.

These are examples of changes which may have happened on your beach in the last sixty years or more.  The nice thing about this project is that action can take place after the research is done.  Beaches can be cleansed of rubble.  Groins can be build to add to beaches.  Regulations can be made or merely enforced.  This kind of project can bring lasting good to a community.

The decline of the fishing industry in the United States is proceeding as it has in many other countries….

Since no one owns the fish no one has an interest in regulating their harvest.  The government has taken this job but as we know the government has many conflicting interests.  In this case, the fish which are allowed to be taken are now smaller and they can be taken from places which are sometimes the breeding grounds of the fishes.  Replacement of the populations must take place, or the breeding stock will have been eaten.

The project for homeschoolers is really a research project.  The student should take one type of fish and trace the regulations governing the harvesting of that fish from about 1900.  Your student can make charts showing the size allowances through the years and the number allowed to be caught.  Remember that commercial fisheries have different rules and allowances for the catch.  Determine the breeding habits of the fish and compare that to the methods be which they are caught.  Remember, this project should be for only one type of fish.

The last topic concerns the uppermost reaches of the oceans:

Life in the oceans depends upon the surface.

The light from the sun hits the surface of the water and is either reflected or is admitted.  The light which penetrates the surface goes down to a point where the light can no longer pass.  This area of upper ocean is the euphotic zone.  In this region, plants can grow using the light from the sun to produce food.  The phytoplankton and zooplankton and the organisms which live off of them all depend upon the transmission of light.  Anything which will block off this light is a hazard to the organisms.  In addition, the dangerous frequencies of light called ultraviolet radiation (UV) can harm the organisms of this region.  If the UV radiation were increasing, the life of the upper region, the euphotic zone, would be in jeopardy.

God designed into the Earth’s ecology, a system of checks and balances, but man’s lack of wisdom may have created umbalances which can jeopardize life in the oceans.  Homeschoolers can measure and research these possible changes.

These facts give us lots of possibilities for research!

Even without a nearby ocean, a homeschooler can get sea salts from the pet store and recreate some of the upper levels of the oceans by adding water.

Using a photocell, a student can measure the light passing through the top few feet of the sea, or through any type of pollution, like suds or oil.  The UV passing through water can be measured by shining a UV light down into the tank at a photocell.

I had one student who hatched brine shrimp (from the local pet store), irradiated them with UV, recorded the results, drew conclusions, and won a science fair competition.

We’ll be posting more articles in the coming weeks on projects and experiments you can do in your homeschool to study the ocean.  Stay tuned!  You may wish to subscribe to the RSS feed so you don’t miss anything!