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Project Design Plan
Everyone knows that water boils at 212°F, but does adding salt to a pot of water make it boil at a higher temperature? Being a person that cooks frequently at home, I wanted to test the debated idea that adding salt to my water will make it boil faster. One of my friends says it does raise the temperature and therefore cooks it faster. My other friend says it only helps it taste better.
Table salt is often added to water before the boiling process in hopes that the water will boil faster. It has been argued that the boiling temperature difference is insignificant with a small pot of water. However, when adding salt to larger amounts of water, the change is more noticeable.
Southwest Research Institute states that the heat capacity of salt water is less than that of pure water, which means that it takes less energy to raise the temperature of the salt water 1° C. than pure water. The time it takes a pot of water to boil is controlled by three things, first is how much heat you put into the pot, second is how fast the temperature rises and third is the boiling point of the liquid (Southwest Research Institute, 2014).
Salt elevates the boiling temperature of water using a process known as boiling point elevation. With water being a known solvent and salt a non-volatile solute, when you add salt to the water, it makes the water an impure solvent, and raises its boiling point above that of pure solvents (Effect of Salt on the Boiling Temperature of Water). Experimental Design Steps
Water will be boiled four different times as follows:
1.2 cups of distilled water are added to a 2 quart cooking pot
a. First run add NO salt – this is the control
b. Second run add 1 Tablespoon of table salt – Trial #1
c. Third run add 1 Tablespoon of table salt – Trial #2
d.Fourth run add 1 Tablespoon of table salt – Trial #3
2. For each run, bring water to boil
3. For each run, record the highest temperature reading of the boiling water
4. After first through third runs, allow pot and burner to cool
5. Wash pot after each run to clean salt residue
A typical recipe will call for a dash of salt in the water. The articles I read made me believe that adding more salt would make the temperature difference more noticeable, I upped the salt to 1 tablespoon of salt to each pot of water per run, instead of a dash. Adding a dash of salt could skew the results, because when adding a dash, you will not have the same measurement of salt to each pot of water as you would when measuring the salt with a tablespoon. In order to reduce error, so I used three trials.
Sequence of Events
During each trial I will be measuring the temperature of the water with a thermometer. Once it reaches its highest temperature, I will record it in my data table. This will be the process for each trial.
Tools, Technologies, and Measurement Units
2 Quart Cooking Pot
Pint measuring cup
Teaspoon and tablespoon measuring spoons
Thermometer (Degrees Fahrenheit)
Stove top burner (electric)
Independent Variable: Amount of salt added to the water
Dependent Variable: Temperature at which the water boils
Controlled Variables: Temperature of stove setting, pot, type of water, brand of salt, amount of water, thermometer
Threat Reduction to Internal Validity
By washing the pot and thermometer between each trial, I will reduce the amount of salt residue that is on the pot that could alter my results. I will use the same heating unit, pot, and thermometer each time to get more valid results.
The hypothesis of this experiment is that adding table salt to water will raise the boiling temperature of the water. Process of Data Collection
Boiling Point of Two Cups of Water
Amount of salt added (IV)
Temperature of boiling water in Fahrenheit (DV)
No Salt (Control)
1 Tablespoon Salt Run #1
1 Tablespoon Salt Run #2
1 Tablespoon Salt Run #3
As predicted, adding salt to water does raise the boiling temperature of the water, even if only minimally. Variations in the boiling temperature may be contributed to slight variations in the measurements of the salt added to the water. It is important to measure both the water and salt accurately to ensure accurate results. Appropriate Methods
For each run, 2 cups of water were added to a 2 quart saucepan; 1 tablespoon of salt was then added to the water and stirred to mix the two ingredients together. The saucepan was then put on the stove and brought to a boil. Once the water reached a full boil the final temperature was recorded using a Go-Temp thermometer. The tools and methods used in this are appropriate to the experiment.
The results were larger than anticipated. The average temperature of the water with the salt was 215.1 degrees Fahrenheit, while the temperature of the control was 212.7 degrees Fahrenheit. This was a difference of 2.4 degrees. Conclusion
Confirmation of Hypothesis
My hypothesis was confirmed. Adding table salt to water causes the water to boil at a higher temperature. The temperature readings were hard to make. Oven mitts had to be worn to keep my hands from getting burned. I had to be sure that the thermometer wasn’t too close to the stove or the temperature would be skewed.
Experimental Design as a Key Factor
How you design your experiment is key to helping you keep your results reliable and valid. You only need one independent variable. If you have more than one, you won’t know which one is actually affecting your results, it will also be harder to measure. Making as many variables as possible constant will help increase the reliability of the experiment.
By following this plan and report, you can replicate this experiment. One might try adding different amounts of salt to see if there is a point at which the amount of salt added stops increasing the boiling point. Evaluation of Validity
Replicating this experiment will add to the validity of my results and others results. If the experiment is replicated numerous times this will add to the
validity, resulting in a more accurate conclusion. It is important to measure both the water and salt accurately to ensure that the results collected are as accurate as possible.
Does water boil faster if you put salt in the water? (n.d.). Retrieved July 19, 2014, from http://www.swri.org/10light/water.htm
EXPERIMENTAL SCIENCE PROJECTS: The Effect of Salt on the Boiling Temperature of Water. (n.d.). Retrieved July 19, 2014, from http://www.freesciencefairproject.com/projects/effect_salt_boiling_water.html
Effect of Salt on the Boiling Temperature of Water. (n.d.). Retrieved July 19, 2014, from http://www.actiondonation.org/articles/effect-of-salt.html
Post navigation. (n.d.). Retrieved July 19, 2014, from http://www.sciencebase.com/science-blog/how-does-salt-affect-the-boiling-point-of-water.html