This experiment investigates the catalytic effect of ash on the combustion of sugar. Initially, an attempt was made to ignite a sugar cube with a lighter, which was unsuccessful. Likewise, ash alone could not be ignited. However, after sprinkling ash onto the sugar cube, the mixture burned with a blue flame. This indicates that certain metal oxides1[chemical compounds of metals with oxygen that often act as catalysts] in the ash act as catalysts2[substances that accelerate a chemical reaction without being consumed] and facilitate the thermal decomposition3[the process by which a substance breaks down into simpler compounds due to heat] of sugar.

Null Hypothesis: Pure ash has no effect on the flammability of sugar.

1. Introduction

Sugar is a carbohydrate with a stable crystalline structure that does not easily ignite under normal conditions. Only at high temperatures does sugar begin to caramelize and eventually char. However, this process can be significantly accelerated by the presence of catalysts. Ash, particularly the residues of burned organic materials, contains metal oxides4[chemical compounds of metals with oxygen that often act as catalysts] and other mineral compounds that function as catalysts for the decomposition of sugar. The aim of this experiment is to investigate the catalytic effect of ash on the combustion of sugar.

2. Material and Methods

Materials:

  • 1 sugar cube
  • Ash (e.g., from a tobacco pipe or burned paper)
  • Lighter or matches
  • Metal spoon or fireproof surface

Procedure:

  1. Place the sugar cube on a non-flammable surface.
  2. Attempt to ignite the sugar cube directly with a lighter.
  3. Observe and document the reaction.
  4. Attempt to ignite a small pile of ash with the lighter and record observations.
  5. Sprinkle a thin layer of ash evenly over the sugar cube.
  6. Hold the lighter to the sugar cube covered in ash and document the reaction.

Throughout the experiment, particular attention is paid to the color and shape of the flame, as well as the speed of combustion.

3. Results

When the sugar cube was heated directly with a lighter, no ignition was observed. Instead, the sugar began to melt and caramelize without producing a flame. Only after prolonged exposure to high temperatures did gradual charring occur, but this did not lead to sustained combustion. The ash, when tested separately with the lighter, also did not ignite. However, once a thin layer of ash was sprinkled onto the sugar cube, the mixture ignited immediately. The reaction proceeded quickly, producing a steady, blue flame. The combustion was significantly more intense than the previous attempt with pure sugar. During the process, no visible soot was formed, and the sugar was almost completely consumed.

4. Discussion

The results clearly demonstrate that ash exerts a catalytic effect on the thermal decomposition [the process by which a substance breaks down into simpler compounds due to heat] of sugar. The primary reaction facilitated here is the thermal decomposition of sucrose (C12H22O11), which is accelerated by the presence of metal oxides.

The thermal decomposition5[the process by which a substance breaks down into simpler compounds due to heat] of sucrose occurs in multiple stages. First, dehydration6[a chemical reaction in which water (H₂O) is removed from a compound] occurs, where sugar loses water under heat and decomposes into carbon and other organic compounds:

C12​H22​O11​ → 12C + 11H2​O

This process normally requires high temperatures, but it is significantly accelerated by the presence of catalysts such as potassium oxide (K2O)7[a basic oxide of the element potassium that reacts with water to form potassium hydroxide] and calcium oxide (CaO)8[a strongly alkaline white powder that reacts with water to form calcium hydroxide, also known as quicklime] in the ash. These metal oxides act as electron acceptors9[substances that receive electrons from another molecule, facilitating a chemical reaction], which promote the thermal breakdown of sugar molecules.

In a second step, the oxidation10[a chemical reaction in which a substance loses electrons, often involving oxygen] of the released carbon leads to the formation of carbon monoxide11[a colorless, odorless, and toxic gas produced during incomplete combustion] and carbon dioxide:

C+{1/2}O_2 right CO

C+O_2 right CO_2

The resulting intermediate products, such as carbon monoxide (CO) and hydrocarbons, can be fully oxidized into carbon dioxide (CO2) and water at higher temperatures:

CO+{1/2}O_2 right CO_2

H_2+{1/2}O_2 right H_2O

Role of Ash as a Catalyst

Ash contains significant amounts of potassium oxide (K2O) and calcium oxide (CaO), which act as catalysts for combustion. Specifically, potassium oxide reacts with water to form potassium hydroxide:

K_2O + H_2O right 2KOH

Potassium hydroxide (KOH) can then interact with the decomposition products of sugar, facilitating electron transfers that promote rapid oxidation.

Explanation of the Blue Flame Coloration

The blue color of the flame suggests that potassium ions (K+) [positively charged potassium atoms that influence flame coloration] are involved in the combustion process. Potassium salts, particularly potassium carbonate (K2CO3)12[a common salt found in ash that acts as a mild alkali], may vaporize at high temperatures and emit blue-violet light when their excited electrons return to the ground state:

Comparison to Other Catalytic Combustion Processes

A similar effect can be observed in chemical reactions involving strong oxidizers, such as potassium permanganate (KMnO4)13[a powerful oxidizing agent that facilitates combustion] or potassium chlorate (KClO3)14[a chemical compound that releases oxygen to accelerate burning], which also accelerate the decomposition of organic substances by releasing oxygen. Similar principles are used in industrial applications, such as sugar processing and pyrotechnics.

Safety Considerations

  • The experiment should be conducted on a fireproof surface.
  • Handling open flames requires caution.
  • Flammable materials should be kept away.
  • The flame can flare up unexpectedly; therefore, a safe distance should be maintained.
  • Ash may contain harmful residues depending on its origin. Direct skin or eye contact should be avoided.



  • 1
    [chemical compounds of metals with oxygen that often act as catalysts]
  • 2
    [substances that accelerate a chemical reaction without being consumed]
  • 3
    [the process by which a substance breaks down into simpler compounds due to heat]
  • 4
    [chemical compounds of metals with oxygen that often act as catalysts]
  • 5
    [the process by which a substance breaks down into simpler compounds due to heat]
  • 6
    [a chemical reaction in which water (H₂O) is removed from a compound]
  • 7
    [a basic oxide of the element potassium that reacts with water to form potassium hydroxide]
  • 8
    [a strongly alkaline white powder that reacts with water to form calcium hydroxide, also known as quicklime]
  • 9
    [substances that receive electrons from another molecule, facilitating a chemical reaction]
  • 10
    [a chemical reaction in which a substance loses electrons, often involving oxygen]
  • 11
    [a colorless, odorless, and toxic gas produced during incomplete combustion]
  • 12
    [a common salt found in ash that acts as a mild alkali]
  • 13
    [a powerful oxidizing agent that facilitates combustion]
  • 14
    [a chemical compound that releases oxygen to accelerate burning]