Abstract

Objective

In this experiment you will learn about soluble and insoluble chemicals, and use the difference in solubility of salt and salt to separate the components of a mixture.

Introduction

Chemistry is the study of matter and how matter behaves and interacts with other kinds of matter. The way that matter behaves is called a "property" of matter. Everything around us is made of matter, and you can explore the properties of matter using some common chemicals around your home.

One important property of matter is called "solubility." We think about solubility when we dissolve something in water. If a chemical is soluble in water, then when you add it to water it will dissolve, or disappear. If it is not soluble, then it will not dissolve and you will still see it floating around in the water.

When you add a soluble chemical to dissolve in water you are making a "solution," and solutions are very important for chemistry. We call the chemical you are adding the "solute" and the liquid that it dissolves in the "solvent." Even though after a solute dissolves in a solvent it becomes invisible, it is still there. If you were to evaporate all of the liquid away from the solution, you would be left with your dry chemical again. In fact, this is how salt is processed in giant salt flats where seawater is slowly evaporated, leaving behind huge amounts of sea salt.

All of the different kinds of matter can be sorted into categories based upon whether they are soluble or not in different solvents. Because of this, the properties and solubility of different chemicals can be used to separate mixtures of chemicals. A chemical mixture is a blend of two or more different kinds of chemicals where the individual chemicals do not react with each other, but remain separate. You can see an example of this when you look closely at a dry mixture of salt and sand.

In this experiment, you will use the different properties of the chemicals in salt and sand to separate a mixture. By doing this, you will learn about the solubility of soluble and insoluble chemicals.

Terms, Concepts, and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• chemical
• crystals
• mixture
• solution
• soluble
• solute
• solvent
• insoluble
• filtration
• evaporation

Bibliography

• This website at Chemistry 4 Kids has a great tutorial on chemistry, matter properties and mixtures. Go check it out:
  Rader, Andrew. 2005. Rader's Chem4Kids. Andrew Rader Studios. 12/13/05.
  http://www.chem4kids.com/files/matter_intro.html
• Here is a fun experiment that explores the relationship between solubility and buoyancy, using salt, water and a golfball:
  Anonymous, 2005. "Lab Zone: Great Salt Golf Ball." Science News for Kids. Washington, D.C. 12/13/05.
  http://www.sciencenewsforkids.org/articles/20051019/LZActivity.asp
• Cobb, Vikki, 1972. "Science Experiments You Can Eat." Harper Collins, New York, NY. 12/13/05
  http://www.vickicobb.com/scienceyoueat.html

Materials and Equipment

• salt
• sand
• tea kettle
• 2 small glass jars with lids
• water
• measuring cup
• funnel
• coffee filter
• magnifying lens

Experimental Procedure

1. Before you begin, you will want to examine your salt and sand closely and make some initial observations. Place some salt and sand on a napkin and using your magnifying glass, make some observations and draw what you see. What do you notice? Record your observations in a data table like the one shown below:
   
   

   	Salt	Sand
   Observations before mixing
   Amount before mixing
   Observations of mixture
   Total amount of mixture
   Observations after adding water
   Observations after separation & drying
   Amount after separation & drying

   
   
   Note: If your sand has a lot of debris in it, use a strainer to purify it.
2. In your glass jar, add 1/4 cup of salt, and 1/4 cup of coarse sand.
3. Put the lid on your jar and shake until the salt and sand are completely mixed together.
4. Using your magnifying lens, look closely at the mixture. What do you notice? Can you still see the individual grains of salt and sand ? Record your observations in your data table.
5. Put the teakettle on the stove, and heat up some boiling water.
6. Pour 1/2 cup of boiling water into your jar and stir with a spoon. Be careful and get help from a parent or adult, the glass will get very hot!
7. Using your magnifying lens, look closely at your solution. What do you notice? Can you still see the individual grains of salt and sand? Record your observations in your data table.
8. Place the coffee filter in the funnel and place the funnel in the top of your second glass jar to make your separation apparatus:
   

9. Slowly pour the solution over your filter, being careful not to pour too much at once. As the solution seeps through the filter, let it collect in your jar.
10. Now look at the coffee filter, what do you see? Carefully scrape off any particles with a spoon and place them into the first glass jar.
11. Place both glass jars onto a cookie sheet, and bake in the oven at 325 degrees until all of the water has evaporated from both of the jars. You will need an adults help with this.
12. Remove the jars and allow them to cool to room temperature before handling. They will be very hot!
13. After the jars are cool, use your magnifying lens to make observations of the two jars. What do you notice? Can you still see the individual grains of salt and sand? Are they mixed together or separated? Record your observations in your data table.
14. Now carefully use a measuring cup to measure the amount of salt and sand you ended up with. Do these amounts match the amounts you started with? Why do you think this happened?

Variations

• Many different chemicals have different solubilities. By adding different amounts of salt, sugar or baking soda to water you can see how soluble each chemical is. Just add each chemical a teaspoon at a time to a glass of water until you notice that it no longer dissolves when you stir it around. Be sure to use the same amount of water for each experiment! The chemical that dissolves the most into the same amount of water is the most soluble, and the chemical that dissolves that least is the least soluble. Try it!
• How might temperature affect the solubility of a chemical? Try dissolving the same amount of sugar in hot water, room temperature water and ice-cold water. What happens? Can you think of other variables that might affect solubility?

• For more science project ideas in this area of science, see Chemistry Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Last edit date: 2010-07-26 12:13:13