Class 12th Chemistry Projects for 2009 Exams
Science Projects Chemistry
Saturated Solutions : Measuring Solubility
The goal of this project is to measure the solubilities of some common
chemicals: table salt (NaCl), Epsom salts (MgSO4), and sugar
A good part of the substances we deal with in daily life, such as milk,
gasoline, shampoo, wood, steel and air are mixtures. When the mixture is homogenous,
that is to say, when its components are intermingled evenly, it is called a
solution. There are various types of solutions, and these can be categorized by
state (gas, liquid, or solid). The chart below gives some examples of solutions
in different states. Many essential chemical reactions and natural processes
occur in liquid solutions, particularly those containing water (aqueous
solutions) because so many things dissolve in water. In fact, water is sometimes
referred to as the universal solvent. The electrical charges in water
molecules help dissolve different kinds of substances. Solutions form when the
force of attraction between solute and solvent is greater than the force of
attraction between the particles in the solute. Two examples of such important
processes are the uptake of nutrients by plants, and the chemical weathering of
minerals. Chemical weathering begins to take place when carbon dioxide in the
air dissolves in rainwater. A solution called carbonic acid is formed. The
process is then completed as the acidic water seeps into rocks and dissolves
underground limestone deposits. Sometimes, the dissolving of soluble minerals in
rocks can even lead to the formation of caves.
State of Solute
|State of Solvent
||State of Solution
|Air, natural gas
|Alcohol in water, antifreeze
|Carbonated water, soda
|Sea water, sugar solution
|Hydrogen in platinum
If one takes a moment to consider aqueous solutions, one quickly observes
that they exhibit many interesting properties. For example, the tap water in
your kitchen sink does not freeze at exactly 0°C. This is because tap water is
not pure water; it contains dissolved solutes. Some tap water, commonly known as
hard water, contains mineral solutes such as calcium carbonate, magnesium
sulfate, calcium chloride, and iron sulfate. Another interesting solution
property is exhibited with salt and ice. Have you ever had the chore of throwing
salt on an icy sidewalk? When the ice begins to melt, the salt dissolves in the
water and forms salt water. What happens to the freezing point of water when
salt is added to it? Even some organisms have evolved to survive freezing water
temperatures with natural "antifreeze." Certain artic fish have blood
containing a high concentration of a specific protein. This protein behaves like
a solute in a solution and lowers the freezing point of the blood. Going to the
other end of the spectrum, one can also observe that the boiling point of a
solution is affected by the addition of a solute. Do eggs cook faster or slower
when salt is added to the pot of water? These two properties, namely
freezing-point depression and boiling-point elevation, are called colligative
properties (properties that depend on the number of molecules, but not on
their chemical nature). Exploring these properties and others of aqueous
solutions are just some of the many ways that you could expand the scope of this
Finally, if you enjoy learning about solutions or other areas of chemistry,
consider a career in the physical sciences. One example is working as an analytical
chemist. Such chemists analyze the chemical composition of substances. They
conduct many experiments to identify special characteristics of substances for a
wide variety of reasons. Perhaps they are charged with testing municipal
drinking water for its purity, or perhaps they must test a forensic sample for
evidence in a trial. Whatever the reason, it is challenging work that requires
precision and creative thought.
In this project you will measure the aqueous solubility of some common
household chemicals: table salt (NaCl), Epsom salts (MgSO4), and
sugar (sucrose, C12H22O11). How much of each
chemical can dissolve in a given volume of water?
Terms, Concepts and Questions to Start Background
To do this project, you should do research that enables you to understand
the following terms and concepts:
- Soluble vs. insoluble
- Chemical structure of water
- Polar molecule
- Force of attraction
- Concentration of a solution
- Dilute vs. concentrated
- Sodium chloride (NaCl)
- Magnesium sulfate (MgSO4)
- Sucrose (C12H22O11)
- What is a saturated solution?
- What is the difference between a saturated solution and an unsaturated
- Any basic physical science text will have a chapter on solutions or
solubility. Begin by reading a chapter on basic solution chemistry, such as
Chapter 4 in:
Haber-Schaim, U., R. Cutting, and H. G. Kirksey, 1999. Introductory
Physical Science, seventh edition, Belmont, MA: Science Curriculum, Inc.
- The Chem4Kids website is a good reference for basic chemistry concepts.
Here is a link to their webpage on solutions:
Andrew Rader Studios, 1997–2007. "Chem4Kids.com: Matter:
Solutions," Chem4Kids.com [accessed October 3, 2007] http://www.chem4kids.com/files/matter_solution.html.
- This website has a collection of demonstration videos illustrating various
properties of solutions:
Maynard, J.H., 1998–2000. "General Chemistry Demonstrations:
Properties of Solutions," University of Wisconsin-Madison, Chemistry
Department, Demonstration Lab [accessed October 3, 2007] http://genchem.chem.wisc.edu/demonstrations/Gen_Chem_Pages/11solutionspage/solutionsmain.htm.
- The experimental procedure is based on:
Materials and Equipment
To do this experiment you will need the following materials and equipment:
- Distilled water
- Metric liquid measuring cup (or graduated cylinder)
- Three clean glass jars or beakers
- Non-iodized table salt (NaCl)
- Epsom salts (MgSO4)
- Sugar (sucrose, C12H22O11)
- Disposable plastic spoons
- Three shallow plates or saucers
- Electronic kitchen balance (accurate to 0.1 g)
Do your background research so that you are familiar with the terms,
concepts, and questions, above.
Determining Solubility: Method 1
- Measure 100 mL of distilled water and pour into a clean, empty beaker or
- Use the kitchen balance to weigh out the suggested amount (see below) of
the solute to be tested.
- 50 g Non-iodized table salt (NaCl)
- 50 g Epsom salts (MgSO4)
- 250 g Sugar (sucrose, C12H22O11)
- Add a small amount of the solute to the water and stir with a clean
disposable spoon until dissolved.
- Repeat this process, always adding a small amount until the solute will no
- Weigh the amount of solute remaining to determine how much was added to
the solution. Save your saturated solutions for the second method.
Determining Solubility: Method 2
- Label the underside of each saucer with tape, one for each solution.
- Weigh the empty saucer and record the weight.
- Pour in 10–15 mL of the appropriate saturated solution (corresponding to
the label on the saucer).
- Weigh the saucer + solution and record the weight.
- Repeat steps 2–4 for each of the three solutions.
- Put the saucers in a warm place (e.g., an oven on low heat) and allow the
water to evaporate.
- Re-weigh the saucers + dry crystals.
- Tip: make sure all the water has evaporated by weighing each saucer
several times, with an interval back in the oven in between, to make
sure the weight is no longer changing.
Analyzing Your Results
- To make sure that your results are reproducible, you should repeat your
solubility experiment at least three separate times for each chemical.
- For each solubility determined by Method 1, you will have the original
volume of water, the total mass of the solute, and the remaining mass of the
solute. You can calculate how much of the solute was dissolved.
- For each solubility determination by Method 2, you will have the mass of
the dry solid after evaporation, and the mass of the original solution. You
can calculate the mass of the water that evaporated.
- Calculate the average solubility, in grams of solute per 100 mL of water,
as determined by each method.
- More advanced students should also calculate the standard deviation of the
solubility, as determined by each method.
- Compare the results of the two methods.
- Compare your results to published solubilities for the three chemicals.
- Let's say that instead of starting with pure water, you tried to dissolve
Epsom salts (MgSO4) in a saturated solution of NaCl. Do you think
this would work? How much MgSO4 would you expect to dissolve?
Would it be more, less or the same amount as in an equal volume of distilled
water? Design an experiment to find out.
- You could also try the experiment above with the other five pair-wise
combinations of the three chemicals.
- Another variation you could try is an experiment on the how fast solutes
dissolve. What can you do to increase the rate at which a solute dissolves
in a solvent? How much more quickly does the solute dissolve, compared to
when the solute is simply added to the solvent?