Defrosting with Alcohols

Can we de-ice a windshield with sanitizer? We tested isopropanol and ethanol at different concentrations to see which was most effective for de-icing at -40C.
Brynn McManes Madison Dooley
Grade 6

Presentation

No video provided

Hypothesis

Our hypothesis is that isopropanol will not freeze at -40 degrees Celsius at a lower concentration than ethanol and therefore be more effective for use in de-icing windshields in winter in Calgary. This is because isopropanol is more commonly found in hand sanitizers and therefore may be more effective.

Research

         

4 Types of Alcohol:

1.       Methanol

2.       Ethyl Alcohol

3.       Isopropyl Alcohol

4.       Ethylene Glycol

January 14, 2024

 

Variables

Manipulated Variables

  • Type of alcohol in the solution
  • Concentration of alcohol in the solution

Responding Variable

  • Freezing point of the solution

Controlled Variables

  • Total volume of solution
  • Experimental setup
  • Ambient (room) temperature

Procedure

Concentration

  1. Used the equation: C1 x V1 = C2 x V2 to figure out V1 with:
    • C1 = the concentration of the alcohol (100% for ethanol and 99% for isopropanol)
    • C2 = the concentration of the solution being tested
    • V2 = the total final volume for the test
    • V1 = the value we solved for, which is the volume of the undiluted alcohol to use
  2. Subtract the volume of alcohol for the test (V1) from the total volume for the test (V2) to determine how much distilled water to add.

Freezer test 

  1. Put on safety gear
  2. Label ice cube trays
  3. Figure out which concentration will go in which spot in the tray (recorded in log book)
  4. Follow concentration procedure to calculate volumes to make concentrations
  5. Measure alcohol for first concentration using graduated cylinder
  6. Add distilled water to make 20 mL total solution
  7. Pour solution into correct spot on tray
  8. Repeat 4-7 until all different concentrations have been added to the trays (one tray for Isopropanol and Ethanol)
  9. Place trays in freezer. Record the time and the freezer temperature when the trays are inserted
  10. Leave thermometer in freezer and check temperature one hour later.
  11. Leave trays in freezer for 25 hours and 47 minutes
  12. Remove trays from freezer and record time and temperature.
  13. Inspect trays and determine which cubes have frozen (use a toothpick to check for solid or not). Record concentrations that did and did not freeze. 
  14. Repeat the test for any concentrations that did not freeze or that were inconclusive (slushy).

Dry ice test 

  1. Put on safety gear
  2. Gather materials
  3. Use data from freezer test to extrapolate concentration for dry ice test
  4. Follow concentration procedure to calculate volumes to make solution
  5. Measure alcohol for first concentration using graduated cylinder
  6. Add distilled water to make 150 mL total solution
  7. Pour solution into the beaker
  8. Place beaker on the magnetic stirrer and add the stirring rod
  9. Set up thermometer on the side of the beaker so it does not touch the beaker or the stirring rod
  10. Wrap the beaker with a towel to help keep the temperature more constant
  11. Start the stirrer
  12. Record the time and temperature
  13. Add dry ice to the beaker and start the timer
  14. Record the temperature every minute
  15. Add dry ice as needed (when the temperature started to increase or the dry ice was observed to have melted)
  16. Continue steps 12 and 13 until the temperature stops changing (consistent for approximately 5 minutes) and the solution gets cloudy/has ice crystals
  17. Add results to extrapolation graphs and extrapolate revised concentration for subsequent dry ice tests.
  18. Repeat steps 4 to 18 as needed until results show concentration has a freezing point of -40 degrees Celsius.

Observations

Ethanol

  • Extrapolation from freezer test predicted 60% concentration at -40ºC

  • Tested 60% concentration and it froze at -41.8ºC.

  • Repeated extrapolation, updated with results from first dry ice test, which predicted 59% concentration at -40ºC

  • Tested 59% concentration and it froze at -39.9ºC

 Isopropanol

  • Extrapolation from freezer test predicted 80% concentration at -40ºC

  • Tested 80% concentration and it froze at -42.8ºC

  • Repeated extrapolation, updated with results from first dry ice test, which predicted 75% concentration at -40ºC

  • Tested 75% concentration and it froze at -26.7ºC

    • Result seemed incorrect compared to predicted results (either 75% or 80% test result seemed to be wrong)

  • Repeated extrapolation, updated with results from previous tests, which predicted 79% concentration at -40ºC

  • Tested 79% concentration and it froze at -30.5ºC

    • 80% concentration result seemed incorrect

    • Retested a 75% concentration (repeated twice to test repeatability)

  • Tested 75% concentration and it froze at -26.1ºC (average for three tests).

  • Repeated extrapolation, discarding the results from the 80% test, which predicted 87% concentration at -40ºC

  • Tested 87% concentration and it froze at -39.4ºC

  • Repeated extrapolation with result from 87% test and confirmed that a concentration of 87.5% was likely to result in a freezing point of -40ºC did not repeat testing due to materials not being available and results being close from 87% test

Analysis

Ethanol 

Isopropanol

Isopropanol - Error Checking

Conclusion

In conclusion, our hypothesis was incorrect. Our experiment found that ethanol can be used at a lower concentration than isopropanol for de-icing at -40 degrees Celsius.

Application

  • The results of our experiment can be used to help people who may need to defrost their windshield without the need to scrape or apply harmful substances or things that can break the windshield. 

  • Repurposing extra hand sanitizer into another useful purpose because many people have extra left hand sanitizer over from the pandemic. 

  • Our experiment found the lowest concentration of alcohol in the hand sanitizer to be effective at -40 degrees Celcius to minimize the cost and potential risks of using alcohol to defrost a windshield.

  • The results of our experiment can be used to help people who may need to defrost their windshield without the need to scrape or apply harmful substances or things that can break the windshield. 

  • Repurposing extra hand sanitizer into another useful purpose because many people have extra left hand sanitizer over from the pandemic. 

  • Our experiment found the lowest concentration of alcohol in the hand sanitizer to be effective at -40 degrees Celcius to minimize the cost and potential risks of using alcohol to defrost a windshield.

Sources Of Error

Freezer Test

  • Concentration of the solution (measured using graduated cylinder that had 0.2mL increments)
  • Incomplete mixing of the solution
  • 1st Trial - additional dilution due to ice maker getting ice into test
  • Variations in freezer temperature during test

Dry Ice Test

  • Concentration of the solution (measured using graduated cylinder that had 0.2mL increments)
  • Volume of dry ice added created some super-cooled measurements that had to be reviewed

Citations

Acknowledgement

We would like to thank the following people for helping us to do our science fair project:

  • Madison’s mom for helping with the scientific method and editing.
  • Madison’s dad for supervising us while using the dry ice.

Attachments

No Log Book Provided