The Effect of Temperature on the Water Solubility of Alum, Baking Soda, Epsom Salt, and Salt


Researched by Jonathan N.


The purpose of this experiment was to determine how temperature affects the dissolving time of various common powders.

I became interested in this idea when I was looking at previous science projects and found people who had done projects to see what kind of aspirin dissolved quickest. Something related to chemistry seemed like a good choice.

The information gained from this experiment could benefit industries, which routinely dissolve huge amounts of substances. It could also benefit just about anyone like a cook who uses dissolving in their daily life.


My hypothesis was the water with the hottest temperature would dissolve the powders the quickest. 

I based my hypothesis on the Encarta Encyclopedia Deluxe, which states that, “Solubility increases with the increasing temperature of the solvent for most substances.” 


The constants in this study were: 
* Area at which experiment is done
* Amount of water (used as the solvent)
* Amount of each solid (used as a solute)
* Procedures
* Kind of cup
* Size of cup
* Timing measurement

The manipulated variable was the temperature of the water.

The responding variable was the time it took for each solid to dissolve. 

To measure the responding variable I used a stopwatch that measured in seconds. 


12 Tsp Alum
12 Tsp Epsom Salt
12 Tsp Baking Soda
12 Tsp Salt
1 Stovetop
1 Sink
12 Cups Water (58 degrees Celsius) 
12 Cups Water (79 degrees Celsius)
12 Cups Water (100 degrees Celsius)
1 Stopwatch
1 Celsius thermometer
1 Bath towel


1. Lay down a bath towel
2. Heat 3 L of water to 58 degrees Celsius.
3. Pour 250 mL of the heated water into a glass.
4. Place 1-tsp of the substance you are testing into the glass and start timing immediately when it is placed in. Stir to help it dissolve.
5. When the substance is done dissolving (so that the substance is no longer visible at all), immediately stop timer and record.
6. Do this four times for each substance using different cups for each trial. 
7. Dump the water in all four glasses into sink and clean thoroughly with soap and water. Dry using a paper towel. 
8. Heat 3 L of water to 70 degrees Celsius.
9. Repeat steps 3-7 to test each substance with the water that is heated to 79 degrees Celsius. 
10. Heat 3 L of water to 100 degrees Celsius.
11. Repeat steps 3-7 to test each substance with the water that is heated to 100 degrees Celsius.
12. When finished experimenting, make sure that all the results are recorded and that the work center is clean.
13. Calculate the average dissolving time for each substance and record.


The original purpose of this experiment was to see how heat affected water’s ability to dissolve various powders.

The results of the experiment were: The water at 100 degrees Celsius dissolved each substance the quickest. The substance that had the least difference in dissolving time between temperatures was salt. The substance that had the biggest difference between temperatures was Alum, which went from the average dissolving time of 21.25 seconds at 79 degrees Celsius to 9.25 seconds at 100 degrees Celsius. 

See the table and graphs below.


My hypothesis was the water with the hottest temperature would dissolve the powders the quickest.

The results indicate that this hypothesis should be accepted.

Because of the results of this experiment, I wonder if different substances, like baking powder, washing detergent, and sugar, would dissolve quicker than any of the substances tested.

If I were to conduct this project again I would conduct more trials for each substance in each temperature. I would use more, different kinds of substances, and I would use more temperatures for conducting the tests.



Uses of Dissolving

Dissolving is used for a great amount of things. It is used by cooks for seasonings and dishes, when preparing laxatives and pain relievers, largely by factories for products, and continuously by scientists for experiments.

Why Solubility is Important

Solubility is very important and is used for a lot of important purposes. Without solubility, nothing would dissolve. Some solutions are very important. Baking soda, for example, is used for cleaning, deodorizing, to relieve heartburn, acid indigestion, sour stomach, and upset stomach.

Epsom salt is used for a laxative and for bathing. Without solubility, baking soda and Epsom salt would be almost useless, along with other substances. 


Dissolving is when a substance merges with a liquid and passes into solution. A solution is a mixture of two or more substances that cannot be separated. A solvent is the substance in which the solute is being dissolved.

The solute is the substance being dissolved in the solvent. A solution becomes saturated when it is no longer able to dissolve any more solute. This is called a saturated solution. 


Chemically, water is H2O. Water molecules are formed when two hydrogen molecules and 1 oxygen molecule combine.


Water is a great solvent for many substances. It is able to attach itself to positive and negative ions, like sodium and chlorine from the compound sodium chloride. That is why different salts dissolve in a water solution. Water can, in the same way, dissolve polar molecules, like ethyl alcohol. 

Water can also dissolve gases. The two most important gases found dissolved in water are carbon dioxide and oxygen. Pure water is unable to penetrate limestone, but when mixed with carbon dioxide, it is able to penetrate it, along with other hard substances. Water that has been combined with carbon dioxide has even carved the biggest underground caves and caverns.


When a substance is cold and does not come in contact with heat, the molecules move slowly. When the substance does come in contact with heat, the vibration becomes rapider and the molecules possess more energy of motion.

Effect on Dissolving

With the increasing temperature of the heat being received by the substance, its solubility increases. Basically, the higher the temperature, the higher the solubility of the substance.


Alum is the name of a particular group of double salts. Double salts consist of two simple salts. Alum is the double salt of hydrated potassium and aluminum sulfate. The compound is called potassium sulfate.

There are also other types of alum. Some are ammonium alum, sodium alum, and potassium chrome alum. Most alums are manufactured from bauxite. Some of alum’s uses are to make glue, dyes, baking powder, and leather tanning agents. Some of the industry uses are to purify water and harden plaster of Paris. 

Sodium Chloride

Salt is a clear, brittle material that is used to preserve and flavor food. It is also used for the manufacture of a large number of chemicals and chemical products. Salt consists of sodium and chlorine. The chemical name for salt is sodium chloride and the mineral name is halite. The formula for salt is NaCl.

It forms clear crystals, mostly perfect cubes. The impurities in it make it appear white, gray, yellow, or red. The source of all salt is the brine of seas, lakes, etc. The deposits that are now underground were formed by the evaporation of seawater millions of years ago. It is necessary for good health. 

Human blood contains salt that is needed for cells to function properly, though studies show that salt or sodium compound can result in high blood pressure. For this reason, people attempt to reduce their sodium intake, and instead use substitutes that do not contain sodium.

Baking Soda

Baking soda is a stomach alkalizer that soothes skin irritations. It is the source of carbon dioxide in baking powders and also in some fire extinguishers. It is a white, crystalline powder, also known as bicarbonate of soda. It is soluble in water and very slightly soluble in alcohol. 

Most acids decompose it. The major use of baking soda is foods. It is used in effervescent salts and is sometimes used to correct excess stomach acidity. Because it is less soluble than the carbonate, carbon dioxide is bubbled into a saturated solution of pure carbonate, and then it precipitates so it can be collected and dried.

Epsom Salt

Epsom salt is a white powder that, in the past, was commonly used as a laxative. It was mixed with water to form a solution for soaking inflamed body parts in. It was also used to temporarily relieve constipation. Now it is rarely used. It is the powder form of magnesium sulfate, and was named for Epsom, England, where it was first obtained.


Water is extremely important. It is used to dissolve substances humans often use. Dissolving is also very important. Heat speeds up the process of dissolving in water.


“Bicarbonate of Soda,” World Book Encyclopedia, 1998, Volume 2, p. 289

Busch, Marianna A.  "Alum," World Book Encyclopedia, 1998, Volume 1, p. 390.

Butt, John B., “Solution,” World Book Encyclopedia, 1998, volume 18, p. 587

Dean, Jr., Walter E.  “Salt,” World Book Encyclopedia,  1998, Volume 17, p. 72

Neufeldt, Victoria and Gurlanik, David B., Webster’s New World Dictionary: Third College Edition, New York, London, Toronto, Sydney, Tokyo, and Singapore, Prentice Hall, 1991, p. 397

Reed, Brian V. “Epsom Salt,” World Book Encyclopedia, 1998, Volume 6, p. 345

“Sodium Bicarbonate,”, 1/21/04

“Water: The Universal Solvent”, The New Book of Popular Science 2000 Edition, Danbury, Connecticut, Grolier, 2000, 83 & 84


I would like to thank the following people for helping make my project possible:
* My dad for aiding me during researching.
* My mom for helping me conduct the experiments and for being willing enough to let me stay after school during the after-school classes. 
* Mr. Newkirk for helping me SO much with this project.

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