Pressure in the Diet CokeTM & MentosTM Reaction


Perform a series of experiments on the reaction between Diet CokeTM and MentosTM candies. Use the data to estimate what the pressure would be inside a sealed 2 L bottle of Diet Coke with 5 Mentos mints.


Your plan should include the following information, but in your own words.

  1. Make a Diet Coke & Mentos fountain.
  2. Set off your fountain & measure the height of the spray.
  3. Repeat with caps that have different size holes.


Write out your detailed procedure. Be sure to descrbe how you made the fountain (include a labeled diagram, the size of the bottle of Diet Coke, number of Mentos and how you attached them together, etc.):

Construction of Diet Coke & Mentos Fountain

and how you measured the height of the spray, using a ruler as a scale hypsometer.

Measuring the height of the spray.

(In the above example, the height of the spray would be 4.5m.)

Data & Observations

Here are data for each of the honors Physics classes:

Block Diameter of hole
Dist. to 2m mark
Height of 2m mark
Dist. to top of spray
Height of spray
A 4.0 11.5 2.0 40.0    
A 4.8 9.0 2.0 34.0    
A 4.8 11.5 2.0 39.0    
A 5.6 12.0 2.0 36.0    
E 4.0 OOPS 2.0 39.0    
E 4.0 14.0 2.0 42.0    
E 4.8 8.0 2.0 28.0    
E 4.8 12.0 2.0 32.0    
E 5.6 11.5 2.0 37.5    
E 5.6 13.5 2.0 42.0    


Calculate the pressure in each bottle using the equation P = ρgh, with ρ = 998 kg/m3, g = 9.8 m/s2, and h as calculated from your measurements. Use the data from your class. If you choose to leave out one or more data points, be sure to include an explanation!

Plot a graph of pressure vs. diameter of the opening. Draw a best-fit line and extrapolate to an opening of 0 mm to find the pressure that would be present in a bottle with no opening.

An example graph with sample data is shown below:

Graph of pressure vs. diameter of opening.

Because you are calculating the pressure with no opening as the y-intercept of your best-fit line, you must either:
  • Calculate the y-intercept graphically, plotting your data points accurately on graph paper and drawing the best-fit line with a straightedge.
  • Calculate the best-fit line and y-intercept statistically, using linear regression. If you do this, be sure to provide the slope, intercept, and correlation coëfficient.
Remember to include possible sources of uncertainty/error.


Last modified: Sunday, 3 June 2012, 1:19 AM