Category: chemistry

Posted on by

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.

Posted on by — 1 Comment

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?
Posted on by

High School Chemistry part 3: Resources for Teaching Chemistry

Chemistry resources are not always limited to what you see in a homeschooling catalog or at a homeschool convention, so here are a few for you to print and save until you need them.

Textbooks:
ChemCom: Chemistry in the Community by the American Chemical Society.  This popular high school level, college prep text is a completely new approach to the topic.  It is not a watered down version but is a good preparation for the SAT II: Chemistry exam.  It covers all of the usual topics, a little more organic chemistry, and a little less physical chemistry.  Going from one chemistry related problem in the community to another, a student studies the theory necessary to deal with the problem.  Lab is done frequently throughout the year and is included in the text.

General Chemistry by Jean Umland:  This college level text is written at the 10th grade reading level.  Designed for high ability, average readers who are college freshmen, this book is a good choice for future science and engineering majors who are homeschooling through high school.  Tested by some homeschoolers in Houston who reported in to the author, this book can be used in self-teaching situations.  It comes with a student study guide, a CD ROM, and keys.  Have your student use this text and prepare for the Advanced Placement test in May.

Chemistry by Jane Chisholm and Mary Johnson.  An excellent summary of the basic parts of chemistry: matter, atoms, physical changes, chemical changes, reactions, metals, acids and bases, organic chemistry, formulas, experiments, and more.  This would be a good book to read to your children leading into discussions.  Usborne recommends age eleven and up.  Fifth grade through seventh seems like a good range.  Some experiments are included.  I was unable to find this on the internet currently in print, but it looks like one that you should be able to find at your local library.

Videos:
The World of Chemistry is a set of video lessons teaching an introductory course at the non-science major, college level freshman year.  A scaled down version for public high school is also available.  I have seen one episode of the high school version and it seemed to be fairly clear and simple.  The set of videos can be purchased in 26 half hour lessons separately or as an entire course.  There are correlating texts available.

Books of experiments and kits:
Doing high school chemistry at home means doing lab, too.  You can do chemistry lab at home easily!  There are many good lab manuals on the market.  Here are a few.  A good place to go for ideas is to a local college bookstore.  There, you will find an entry-level lab manual, perhaps even one using little or no extra equipment.

Chemistry Experiments by Mary Johnson.  An excellent book of experiments using simple home equipment and chemicals.  The experiments use some imaginative methods to keep the equipment within the common type found around the home.  Some explanations and safety recommendations seem to be too brief.  Recommended.

The Usborne Book of Science Experiments by Jane Bingham.  This book of experiments is for older children (ten and up), and as you would expect, the experiments are more difficult than the Science Activity book above.  Physics, chemistry, and technology are some of the topics.  This would be a good manual to use at the junior high level for science lab (not the text).  Please have the child make a write-up of the experiments he performs, though, with an emphasis on the conclusion step to check for understanding of the principle.  Recommended.

Experiences in Chemistry by Kathleen Julicher.  This is a laboratory manual written specifically for home and other small schools.  At the secondary level, the manual meets requirements for a high school chemistry lab, but can be used at the junior high level with interested students.   Equipment and chemical kits are available to homeschoolers from Home Science Tools.  The simple experiments are based on sound fundamentals and the questions relate the principles to everyday life. 

Cooking and Science by Joseph Julicher.  This workbook uses some classic recipes to teach fundamental chemistry.  Equipment is simple since you already have it in your kitchen.  Prelab and postlab questions require high school level knowledge of chemistry.

Chemical Magic from the Grocery Store by Andy Sae.  Fifty-nine activities are in this book, all designed to generate curiosity about chemistry, demonstrate principles, and dispel “chemophobia.”  Not designed to be a comprehensive lab manual for high school students, it is still full of activities that can be done at home and with little material.

A Laboratory Manual: Experience the Extraordinary Chemistry of Ordinary Things  by B. Coburn Richardson and Thomas G. Chasteen.  This is a lab manual designed for the non-science oriented kid.  There are twenty-seven well-explained experiments.  These labs were chosen for their interest, use of normal things (like aluminum cans) familiarity of reactions, and challenge, although some of the labs require lab equipment most homeschoolers will not have.

MicroChemistry by Tom Russo.  These lab manuals are designed to get students a taste of chemistry lab without the amount of chemicals usually used in laboratories.  The students use very small portion and instead of test tubes, use plastic depression plates.  I have used several of the experiments out of Book I and enjoyed its clarity of explanation.  Comes with a teacher’s guide with complete details about preparing the chemicals and lab equipment.  Also has levels II and III available.
References:
Essential Chemistry by Clive Gifford.  Filled with the key principles of chemistry, this book could easily be a study guide for high school chemistry.  This book is very good and concise in its writing.

Dictionary of Chemistry by Jane Wertheim, Chris Oxlade and Dr. John Waterhouse.  Usborne recommends using this book as a dictionary supplement to a textbook and as a review guide.  Both of those sound like an excellent way to use a book filled with well-made charts and easy to understand commentary.  A bonus in the appendix is the list of good experiments.  Some of these can be done at home with a few moderate equipment purchases.

Magazines and More:
ChemMatters by the American Chemical Society.  This is a great little magazine for the chemistry student.  The publication is sixteen pages full of anecdotes and interesting stories concerning chemistry in the world around us.  You can subscribe to the magazine for $14 for a year (4 issues) or read selected articles online.

Cliff Notes: Chemistry  This online guide is pretty fundamental and has most of the topics from high school chemistry.  Missing some detail, it can serve as an alternative way to review some chemistry, not as a primary source.

Part 1: High School Chemistry
Part 2: Myths about Teaching Chemistry