Special Effects: Pyrotechnics, Combustion, and Thermal Decomposition

Pyrotechnics is a specialized field responsible for the creation and management of fire, explosions, and detonations in action scenes.
While Computer-Generated Imagery (CGI) is used for larger effects, real explosions and fire remain popular for shooting close-up shots to ensure realism.
The primary role of the pyrotechnics team is to manipulate fire to make it appear intense and deadly for cinematic purposes.

Combustion is the scientific term for burning.
In a combustion reaction, a fuel is heated and undergoes a chemical reaction with oxygen.
The fire triangle is a conceptual model summarizing the three essential components required for combustion to occur:
- Fuel
- Heat
- Oxygen
If any one of these three components is removed, the fire is extinguished.
Combustion reactions are exothermic, meaning they release useful thermal energy (heat).
Applications of combustion reactions include:
- Heating homes.
- Powering the majority of cars.
- Generating electricity.

Methane ( $CH_4$ ) is a common fuel used in laboratory Bunsen burners, domestic gas cookers, and home boilers.
Methane is classified as a hydrocarbon.
A hydrocarbon is defined as a chemical compound made exclusively from the elements hydrogen and carbon.
Relevant elements and compounds involved in combustion include:
- Alcohol
- Hydrogen
- Carbon
- Oxygen
- Nitrogen

An experiment is conducted to compare the efficiency and products of different Bunsen burner flames (Safety vs. Roaring).
Materials required:
- Bunsen burner
- Heat-proof mat
- Safety goggles
- Tripod
- Two gauzes
- Two beakers
- Thermometer
- Stopwatch
Experimental Procedure:
1. Measure $100\,cm^3$ of water into a small beaker and record the initial temperature in degrees Celsius ( $^\circ C$ ).
2. Place the beaker on a gauze atop a tripod.
3. Heat the water for exactly $1\,\text{minute}$ using the orange 'safety' flame.
4. Move the Bunsen burner aside, record the final temperature, and calculate the change in temperature.
5. Observe and describe the physical appearance of the bottom of the gauze (looking for soot or discoloration).
6. Repeat the process using a second beaker with fresh $100\,cm^3$ of cold water, this time using the blue 'roaring' flame for $1\,\text{minute}$ .
The data is recorded in a table with the following columns:
- Flame Type (Roaring vs. Safety)
- Starting temperature ( $^\circ C$ )
- End temperature ( $^\circ C$ )
- Change in temperature ( $^\circ C$ )
- Observations of gauze and beaker

Complete Combustion:
- Occurs when there is an excess of oxygen available.
- The only products formed are carbon dioxide ( $CO_2$ ) and water ( $H_2O$ ).
- General word equation: $\text{Hydrocarbon} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water}$ .
- Chemical equation for methane: $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$ .
Incomplete Combustion:
- Occurs when there is an insufficient supply of oxygen.
- The products include water ( $H_2O$ ), carbon monoxide ( $CO$ ), and carbon ( $C$ ), which appears as soot.
- In some instances, carbon dioxide ( $CO_2$ ) may also be produced.
- Example word equation: $\text{Methane} + \text{Oxygen} \rightarrow \text{Carbon Monoxide} + \text{Carbon} + \text{Water}$ .
- Example chemical equation: $3CH_4(g) + 4O_2(g) \rightarrow 2CO(g) + C(s) + 6H_2O(g)$ .
- Visual indicators: Fires with enough oxygen tend to burn cleaner/bluer, while those without enough oxygen produce visible smoke or soot (yellow/orange flames).

A decomposition reaction is a chemical process involving the breakdown of a single substance into at least two different products.
Example of general decomposition: The breakdown of hydrogen peroxide into oxygen and water.
Thermal decomposition is a specific type of decomposition that utilizes heat to achieve the breakdown of a substance.
Metal carbonates often undergo thermal decomposition.
Example: The thermal decomposition of calcium carbonate ( $CaCO_3$ ) produces calcium oxide ( $CaO$ ) and carbon dioxide ( $CO_2$ ).
- Word equation: $\text{Calcium carbonate} \xrightarrow{\text{heat}} \text{Calcium oxide} + \text{Carbon dioxide}$ .

Distinguishing between combustion and thermal decomposition depends on identifying if the substance is reacting with oxygen (combustion) or breaking down due to heat (decomposition).
Case Studies:
1. $\text{Iron} + \text{Oxygen} \rightarrow \text{Iron oxide}$ : This is a combustion reaction.
2. $\text{Calcium carbonate} \rightarrow \text{Calcium oxide} + \text{Carbon dioxide}$ : This is a thermal decomposition reaction.
3. $\text{Wax} + \text{Oxygen} \rightarrow \text{Water} + \text{Carbon dioxide}$ : This is a combustion reaction.
4. $\text{Hydrogen} + \text{Oxygen} \rightarrow \text{Water}$ : This is a combustion reaction.
5. $\text{Copper carbonate} \rightarrow \text{Copper oxide} + \text{Carbon dioxide}$ : This is a thermal decomposition reaction.

Education Requirements:
- A Bachelor's degree in Chemical Engineering or Chemistry is typically required.
- Professional certification and specialized training in fireworks and pyrotechnic handling.
Additional Necessary Skills:
- Creativity for designing visual effects.
- Self-motivation.
- Significant interest in the principles of chemistry and physics.