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Evaporation & Cooling

Background Information:

      In my science fair project, I am trying to find out how evaporation affects heating and cooling. Evaporation is the process where molecules in a liquid escape into a gas phase. The project will show how it affects cooling and heating in buildings and the skin. It will also show how energy can be wasted through evaporative cooling with boiling water.  Liquids are more volatile than others because certain liquids, such as alcohol, evaporate at a lower temperature. Volatility means to evaporate quickly. When you pour rubbing alcohol on your skin, it cools your skin more than water because of the rubbing alcohol volatility. The rate of cooling caused by evaporation depends on the rate at which molecules can escape from the liquid.

      Evaporative cooling works on the principle of heat absorption by moisture evaporation. It is nature’s cooling through the evaporation of water. Evaporative coolers are also known as swamp coolers. Swamp coolers are most often used in hot and dry areas. Dogs do not sweat, but their cooling mechanism is similar to humans cooling mechanism. Even if dogs don’t sweat there is a certain way that the excess heat is removed.  

Question: How does evaporation affect heating and cooling? 

Hypothesis:

I think that the pot that is covered would boil the fastest. With the cover on the pot it causes the water to evaporate faster and it uses less energy than the pot with the cover. This affects heating. I think that the rubbing alcohol will evaporate the fastest because it is more volatile than water. This affects cooling. 

Variables:

      Manipulated- water, temperature

      Responding-water, rubbing alcohol

      Controlled-stovetop

Materials:

Measuring Cups

Water

Rubbing Alcohol

Cooking Oil

Plastic Plates

Paper Towels

Clear Tape

Ballpoint Pen

Infrared Thermometer

Stop Watch

Small Fan

Two Pots of Boiled Water

Stove Top 
 

Procedure:

Evaporative Cooling in Buildings

  1. Fill a measuring cup with tap water and allow it to come to room temperature.
  2. Place four disposable plastic plates, with the up sides down, on a work surface.
  3. Fold each paper towel in half twice.
  4. Place a folded paper towel on top of each plate.
  5. Tape the edges of the paper towels to the plates.
  6. Label the paper towels 1, 2, 3, and 4.
  •  
    1. The paper towels will be labeled as:
  •  
    1. Start the stopwatch.
    2. Take the temperature of the paper towels with the infrared thermometer. Take three readings of each paper towel. Record the temperatures and times.
    3. Pour water on paper towel #2, enough to wet it.
    4. Pour rubbing alcohol on paper towel #3, enough to wet it.
    5. Pour oil on paper towel #4, enough to wet it.
    6. Take the temperature of each paper towel, and record the temperature and time in your lab notebook.
    7. Repeat the temperature readings three more times.
    8. Record your observations.
    9. Repeat steps 1-14 two more times, with fresh paper towels, but you can rinse and reuse the plates. Average the results.
    10. Repeat steps 1-15 three more times, only for these trials, with the fan gently blowing over the paper towels. Record the temperatures.
    1. Mark a small spot on your arm with a ballpoint pen.
    2. Measure the temperature of the skin on your forearm near the pen mark.
    1. Pour some room temperature water on your arm.
    2. Take the temperature of your skin near the mark. Record all data.
    3. Take a temperature reading every minute until your arm dries.
    4. Repeat steps 1-5 two more times.
    5. Repeat steps 1-6 of this section three times, this time using the fan or helper with the paper plate to blow air on your arm. Average all of the results.
    6. Graph your results.
    7. Repeat steps 1-9 of this section using rubbing alcohol.
    1. Add 8 cups of tap water to each pot.
    2. Check the starting temperature of the water with the infrared thermometer. Record the time and temperatures.
    3. Start two burners on your stovetop. They should be set to the same setting.
    4. Cover one of the pots with a lid, but not the other.
    5. Put the pots on the burners.
    6. Use the infrared thermometer to record the temperature of the water every 3 minutes.
    1. Determine how long it takes for the water in each pot to come to a boil.
    2. Stop taking the temperature of a pot when it is at a full boil. Decide if the water is at a boiling point. Repeat two more times and average your results. Make a graph.
    •  
         
    •  
      •  
        • 1: no liquid
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      •  
           
    •  
      •  
        • 2: water
    •  
      •  
           
    •  
      •  
        • 3: rubbing alcohol
    •  
      •  
           
    •  
      •  
        • 4: oil
  •  
    Evaporative Cooling on Skin

    Take two more readings and average them.

     
    Evaporative Cooling When Boiling Water

    Measure the temperature of the open pot by pointing the thermometer at the surface of the water. Measure the temperature of the covered pot for a split second removing the lid and pointing the thermometer at the surface of the water.

     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
    Tables for Evaporative Cooling in buildings. 

    These tables represent evaporation cooling in buildings. 1 stands for no liquid, 2 stands for water, 3 stands for rubbing alcohol, and 4 stands for oil. 
     

    •  
      •  
        •  
          •  
              Time 1 2 3 4
              2 27.7 27.3 27.5 27.4
              4 27.4 25.4 21.7 25.8
              6 26 23 17.9 25.2
              8 24.8 21.3 17.7 24.6
              10 25.2 20.5 16.3 24.3
                         
              Trial 2        
              Time 1 2 3 4  
              2 26.6 26.8 26.9 26.6  
              4 26.6 24.2 23.1 26  
              6 25.2 22.2 20.2 25.2  
              8 24.2 20.8 18.3 24.2  
              10 24.7 20.6 18.8 24.7  
                         
                       
              Trial 3        
              Time 1 2 3 4  
              2 27.3 27.3 27.7 26.7  
              4 26.8 24.2 20.7 26.5  
              6 25.4 22.2 17.9 25.8  
              8 24.7 22.6 17.2 24.7  
              10 24.7 20.7 17.7 24.8  

     
     
     
     
     

     
     
     
     
     
     
     
     
     
     
    Trial 1
               
    Time 1 2 3 4  
    2 27.4 27.5 27.2 26.8  
    4 25.5 18.4 13 24.9  
    6 24.8 17.6 13.5 24.8  
    8 24.6 16.9 14.4 24  
    10 24 15.5 15.3 24.6  
                 
    Trial 2          
    Time 1 2 3 4  
    2 26.1 26.5 26 25.3  
    4 25.5 19.8 15.5 24.2  
    6 24.4 18 14.3 24.1  
    8 23.8 16.5 13.8 24.3  
    10 24.1 17.4 15 24.8  
                 
    Trial 3        
    Time 1 2 3 4
    2 27.1 26.1 25.5 25.6
    4 25.7 22.3 17.1 26
    6 25.5 19.5 15.1 24.9
    8 24.5 18.2 14 25.5
    10 24.5 18 14.5 25.6

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    This table shows the average of the paper towels temperatures that were not fanned. 3 which represent the rubbing alcohol had the lowest temperature among the no liquid, the water and the oil. 1 represents the no liquid had the highest temperature. 

      1 2 3 4
    Trial 1 26.22 23.5 20.22 25.46
    Trial 2 25.46 22.92 21.46 25.34
    Trial 3 25.78 23.4 20.24 25.7

     
     
     
     
     
     
     
    This table shows the average of the paper towels temperatures that were fanned. The rubbing alcohol had the lowest temperature when it was fanned. The no liquid paper towel had the highest temperature when it was fanned. 

      1 2 3 4
    Trail 1 25.26 19.18 16.68 25.02
    Trial 2 24.78 19.64 16.92 24.54
    Trial 3 26.46 20.82 17.24 25.52
             

     
     
    Tables for Evaporative Cooling on skin.

    Time Temperature   Time Temperature   Time Temperature
    Start: 1 29.6   Start: 1 28.3   Start: 1 27
    2 29.4   2 26.9   2 25.4
    3 29.5   3 27.4   3 25
    4 28.6   4 26.2   4 25.3
    5 29.1   5 25   5 26.3
    Average 29.24   Average 26.76   Average 25.8

    This is the evaporative cooling of skin. These data tables represent the temperature and time for the water to evaporate without a fan. 
     

    Trial 1                                               Trial 2          Trial 3 
     
     
     

    This is evaporative cooling on skin using a fan. These data tables represent the temperature and time for the water to evaporate with a fan. 

    Trial 1                                                Trial 2            Trial 3 

    Time Temperature   Time Temperature   Time Temperature
    Start:1 27.1   Start: 1 26.1   Start:1 29.4
    2 22.4   2 23   2 25.5
    3 23.6   3 22.3   3 22.9
    4 22.4   4 18.9   4 26.4
    5 25.8   5 19.6   Average 26.05
    Average 24.26   6 20.9      
          Average 21.8      

     
     
    These three tables represent evaporative cooling on skin with rubbing alcohol without a fan. The average temperatures for each trial were the same.

      Trial 1                                            

    Time Temperature
       Start:1 35.6
    2 30.9
    3 29.9
    4 30.6
    Average 31.75

    Trial 2

    Time Your browser may not support display of this image.Temperature
    Start:   1 34.3
    2 30.8
    3 30
    Average 31.7
       
     
    Trial 3
     
    Time Temperature
    Start:   1 34
    2 30.9
    3 30.2
    Average 31.7
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    Trial 1  
    Time Temperature
    Start:   1 32
    2 26.5
    3 24.8
    Average 27.77
     
     
    Trial 2
     
    Time Temperature
    Start:   1 31.7
    2 26.3
    3 28.8
    Average 28.93
     
    Trial 3
     
    Time Temperature
    Start:1 30.7
    2 24.2
    3 26.7
    Average 27.2

     
    Table for Boiling water with and without a lid and the effect of Evaporative Cooling.

    This table shows the boiling point for the covered pot was 12 minutes at 200 degrees Celsius and the uncovered boiling point was 21 minutes for 200 degrees Celsius. 

    Trial 1

    covered uncovered Time (minutes)
    93.8 91.9 Start                    0
    111 104 3
    160 126 6
    190 150 9
    200 160 12
      170 15
      180 18
      200 21

     
     
     
     
    This table shows the boiling point for the covered point was 103.4 degrees Celsius at 21 minutes and the uncovered pot boiled at 93.3 degrees Celsius for 36 minutes. 

    Trial 2

    Time covered uncovered
    Start 32 33.9
    3 45.6 45
    6 59.5 53.6
    9 73.1 62.8
    12 82 71.9
    15 90.3 78.4
    18 97.6 82.5
    21 103.4 85.9
    24   89.3
    27   92.1
    30   92.9
    33   93.5
    36   93.3

     
     
     
     
     
     
     
     
     
    This table shows the boiling point for the covered point was 97.9 degrees Celsius at 9 minutes and the uncovered pot boiled at 98.2 degrees Celsius for 21 minutes. 
     

    Trial 3:

    Time covered uncovered
    Start 36.8 27.4
    3 59.1 39.1
    6 77.2 58.4
    9 97.9 68.4
    12   77.6
    15   84.4
    18   91.4
    21   98.2

     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
    Graph

    These graphs show the time and the temperature that the covered and uncovered pots boiled for.

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    Analysis:

           In the experiment testing evaporative cooling in buildings the paper towel that had the lowest temperature in the evaporative cooling in buildings was the rubbing alcohol with the fan. The largest temperature difference in the paper towels was between the rubbing alcohol and the oil. The rubbing alcohol and then the water had the lowest temperature with the fan. The experiment proved that the substance that had the most volatility (greater tendency to evaporate) was the rubbing alcohol. The rubbing alcohol with the fan experiment shows the effectiveness of swamp coolers cooling buildings because it is the same concept of a fan blowing and helping cool air to travel around a building. 

             In the experiment showing the evaporative cooling on skin the rubbing alcohol with the fan cooled the skin to the lowest temperature before evaporating. The rubbing alcohol had the lowest temperature and when it evaporated the temperature rose back up almost to the starting point temperature. The water with the fan was the second lowest temperature. The experiment with the fan cooled the body more efficiently than without the fan.

                In the experiment of the boiling water with and without a lid, the pot with the lid got to boiling point much faster than the pot without the lid. This happened because the pot with the lid was not exposed to evaporative cooling in the kitchen but the pot without the lid was exposed and this prevented it from reaching boiling point as quickly as the covered pot. This proved how energy can be wasted through evaporative cooling in the kitchen.  

    Conclusion:

          My project shows how evaporation affects heating and cooling in different environments: the human skin, and in buildings and boiling water. Evaporative cooling is nature’s most efficient way of cooling through the evaporation of water.  When heat is added to water and causes it to boil, energy is lost in the evaporative cooling. Sweating by humans is a physiological reaction that uses evaporative cooling as a mechanism to eliminate extra heat. In my experiment, there are two beneficial aspects of evaporating cooling. It is used to cool down buildings and the other is to regulate human skin.  

             Evaporative cooling can be energy waste as shown in boiling water without a lid. In order to not waste energy, use a lid and you will cut down on energy waste. Using a lid saves more energy because it takes less time to boil. Energy can be saved in buildings by using evaporative coolers. Evaporating coolers are appliances that use air flow to distribute cool air and ventilation in a building or home.  This will save a lot of energy instead of using air conditioner units which use a lot of energy and create high electricity bills. Swamp coolers also supply fresh and filtered air.

          There were problems to the connections of this experiment to the real world. If I could add another liquid to my experiment, it would be milk. I want to see if the temperature increases or if it decreases for evaporative cooling in buildings. I also want to see if it affects the temperature on the skin. I want to see if it evaporates quicker or slower than rubbing alcohol and water. 
     
     
     
     
     

    Bibliography

    Science Buddies. http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p071.shtml

    Chem4Kids. http://www.chem4kids.com/files/matter_evap.html

    Air & Water, Inc. http://www.air-n-water.com/faq_swamp.htm

    http://ezinearticles.com/?expert=Ray_Douglas

    http://www.air-conditioner-home.com/Swamp-Cooler-Info/