Smashing Thermit Reaction
Publication No. 12008
Take two rusty iron balls, wrap one in aluminum foil, then bang them together and watch the sparks fly!
Rusted iron balls, 2½" diameter, 2
This demonstration will produce sparks that may shoot several feet. Wear protective goggles or safety glasses and gloves when performing this demonstration. The balls are heavy. Make sure to have a tight grip on the balls before striking them together. Keep fingers to the side of the balls so they are not pinched. Take care to avoid causing hand, arm or shoulder pain from repeated strikes. A teacher demonstration only. Do not allow students to perform this demonstration.
The iron balls may be reused many times and ultimately be disposed of in the trash according to Flinn Suggested Disposal Method #26a. See Tips for procedure to clean and recharge balls with rust.
Student Worksheet PDF
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesDeveloping and using models
Disciplinary Core IdeasMS-PS1.B: Chemical Reactions
HS-PS1.A: Structure and Properties of Matter
HS-PS1.B: Chemical Reactions
Crosscutting ConceptsSystems and system models
Energy and matter
MS-PS1-2. Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
Answers to Questions
The reaction is the same as the classic thermit reaction but much safer. When the balls are struck, the rust (Fe2O3) reacts with the aluminum foil (Al) to produce aluminum oxide (Al2O3), elemental iron (Fe) and heat. This reaction is a highly exothermic, single replacement reaction. Aluminum is oxidized and iron is reduced. The melting point of iron is 1530 °C and the reaction temperature reaches approximately 2200 °C. (ΔH° = –849 kJ/mole)
Fe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(s) + heat
The reaction coordinate diagram for this reaction is shown in Figure 2.
The activation energy (Eact) needed for the reaction to occur is provided by the mechanical (kinetic) energy of the iron balls being struck against one another and the aluminum foil. Once the activation energy is reached, the reaction proceeds very rapidly to produce the products and heat. The loud noise and the sparks result from the large amount of thermal energy (ΔH) released by the reaction.
This demonstration originated from the work of Troy Lilly, Western Texas College, Snyder, Texas, and was first presented to Flinn Scientific by Larry Peck, Texas A&M University, at the 16th Biennial Conference on Chemical Education. Special thanks to Alan Slater, retired, Stratford Central Secondary School, Stratford, Ontario, who provided Flinn Scientific with instructions for this activity.