A coffee mate fireball

Coffee mate is a powdered coffee that you would mix with water (hot or cold) to make a cup of coffee. But who knew that it was flammable! Coffee mate would not ignite when on a tea spoon but when it is suspended in the air the surface area is increased. Therefore a greater amount of oxygen can react with the coffee mate so it can be ignited and produce a fireball. A fireball is cause due to the individual particles of coffee mate catching alight and then producing enough heat to catch the nearby particles producing a chain reaction. Coffee mate behaves just like flour or corn flour in terms of it being a fugitive dust, which Harwood (p19) defines as a ‘combustible particle of a particular size’. The U.S. EPA states that a suspended particle can have an aerodynamic diameter of not greater than 30 micrometers

Here are two videos to show the ignition and combustion of corn flour and then white flour; white flour for this demonstration had to be sieved to gain the find powdered needed:

Corn Flour from 1veritasium (2012)

White Flour from Science fix (2011)

Fugitive dust can be extremely dangerous and can be explosive in the right conditions and settings. Both the Saif Corporation (p3) and Harwood give an example of a ‘Dust fire and Explosion Pentagon’. This gives us the five things we need for a dust explosion: ‘Ignition’, ‘confinement of dust cloud’, ‘oxygen in air’, ‘combustible dust’ and ‘dispersion of dust particulates’. Once all these factors are present a dust explosion will occur, this is known as the primary dust explosion. If there is any dust suspended in the air nearby or a large amount of settled dust nearby a secondary explosion can take place; this secondary explosion can be far more powerful than the first. The diagram below from Harwood (p10) shows how the primary explosion can serve as an ignition for the secondary explosion: 

This just shows how dangerous it was in flour mills will all that flour dust hanging round in the air in the confined space; just like a time bomb ready to explode...

 Biography

Harwood, S. Combustible Dust: Safety and Injury Prevention. Kirkwood Community College: Community Training and Response Center. [Online].
Available at: http://www.osha.gov/dte/grant_materials/fy08/sh-17797-08/cd_instructor_manual.pdf (accessed 12 March 2013).

 Saif Corporation. (2011) Combustible dust. SAIF Corporation: Industrial Hygiene. [Online]
Available at: http://www.saif.com/_files/SafetyHealthGuides/Combustible_Dust.pdf (Accessed 19th April 2013).

 Sciencefix (2011) Flour Fireball.
Available at: http://www.youtube.com/watch?v=64Ej0sQveT8 (accessed 6th April 2013).

 U.S. EPA. Fugitive Dust Sources. US Environmental Protection Agency. [Online]
Available at: http://www.epa.gov/ttnchie1/ap42/ch13/final/c13s02.pdf (accessed 7th April 2013).

1veritasium (2012) Corn Flour Fireball.
Available at: http://www.youtube.com/watch?v=uWEp_4fHX4Y (accessed 10th April 2013).

Soil pH Tests

Follow up from the pH investigation.

Whilst in the woods on Monday 15^th of April our group decided that we could try and measure the pH levels within the soil around certain trees. This experiment was carried out to investigate whether or not the acidity levels in the soil would differ from tree to tree within a fairly localised area.

The key questions we wanted to be able to answer form this experiment were:

1.     If the acidity level within the ground would change from plant to plant and from tree to tree?

Here are the answers we found for the question.

We looked at three different trees/ plants and took two measurements of the soil from different sides of the plants to make the test fairer.

We used barium sulphate  (this is used to help separate the soil grains so the soil goes into suspension) and pH indicator solution to determine the pH of the soil. We did this by:

1.     Digging a small amount of soil around the plant and putting this into a test tube.

2.     We then added the barium sulphate ( one spatula).

3.     After the powder had settled, we added distilled water to the test tube to fill it to half way.

4.     We then added 10ml of pH indicator solution.

5.     We shook the test tube and left to settle.

This particular sample of soil was taken from a cherry laurel. This was the less acidic than the black thorn and less alkaline than the lime tree so we decided as a group to give this a 7.0 on the pH scale.

This sample came from a Black Thorn. This was the only acidic soil we found whilst taking our six samples throughout the woods. As a group we decided to give this a 5.0 on the pH scale.

This is a sample of soil taken from the bottom of a lime tree. This was the most alkaline of all of the soils tested. As a group we decided that this was a 7.5 on the pH scale.

The measurements that were taken twice as to give a more accurate representation of the pH levels within the soil around the plants. We did this because the soil around the forest is very chalky and we did not want this to have a noticeable impact on the pH levels.  We also did this test twice to make sure that the results were accurate with each other, as you can see from the 3 photos that have been taken, both tubes in all three photos are similar in colour even though they were taken from slightly different patches of soil. This shows that our results were more accurate.