A forensic chemistry lab does not change the content of the course: it changes the question. Instead of following a recipe until the right number appears, the student is handed a case —a chemical burn, a fire, an unidentified sample— and has to gather evidence, analyse the data and defend a conclusion. Stoichiometry, thermochemistry and separation science are all still there; what gets added is a reason to use them.
The three experiments covered here come from Vernier's Forensic Chemistry Experiments lab book and were presented by three teachers —Anne Lavelle, Randy Booth and Nüs Hisim— in a Vernier webinar for the NSTA. All three work in secondary school, in pre-university courses such as AP or IB, and in introductory university chemistry, with the same Go Direct® ecosystem Districalc distributes across Latin America.
Why does the forensic framing work in chemistry?
The practical difference between a traditional lab and a forensic one is who asks the question. In the first, the procedure already contains the answer and the student checks that the measurement matches. In the second, the student has an open case and must decide what to measure, how to measure it, and how far the data supports an accusation. That difference is what turns a routine titration into an argument that has to be defended in front of the class.
The other, less obvious effect is curricular: the same forensic case can be pitched at three different levels without rewriting the lab. The base procedure suits a secondary course; adding the dilution calculations and the derivative analysis turns it into a pre-university or first-year university investigation. The lab is the same; what changes is how much is asked of the student.
"It is applicable for all levels."Anne Lavelle, chemistry teacher, Magnificat High School (Ohio), on the forensic titration lab
Experiment 1 · Messed-up makeup: an acid-base titration with a case behind it
The case: a stage performer suffered chemical burns after using a contaminated makeup remover. The question the class has to answer is how much sodium hydroxide was added to the product.
Students titrate a sample of the makeup remover against a hydrochloric acid solution of known concentration, follow the pH curve in real time, locate the equivalence point and, from there, calculate the sodium hydroxide concentration and the total mass added to the product. The result is not "right" or "wrong" in the abstract: it is the figure with which the class supports or discards the tampering hypothesis.
Concepts covered
- Acid-base neutralisation
- Dilution calculations
- Reading pH curves and the equivalence point
- Stoichiometry
- Data analysis and interpretation
How to adapt it by level
- Entry level (general secondary): the equations are provided ready-made, the drop counter is skipped and students work with the pH sensor alone.
- Intermediate (science-track courses): most of the lab is kept, but the derivative analysis is left out.
- Advanced (pre-university AP or IB, and first-year university): the full dilution calculation, the drop counter setup and the first- and second-derivative analysis are all included.
Equipment: Go Direct® pH Sensor, Go Direct® Drop Counter and Vernier Graphical Analysis.
Experiment 2 · Burning accelerants: calorimetry applied to a fire
The case: students act as forensic analysts and compare the accelerant sample collected at the scene with the samples seized from two suspects.
The setup is deliberately simple: each fuel sample is burned under an aluminium can of water, the temperature change is recorded, and the heat of combustion of each accelerant is calculated. With those three values in hand, the class decides which of the two suspects had the same fuel that turned up at the scene. It is the same calorimetry as always; the difference is that the final number points at someone.
Concepts covered
- Energy transfer
- Heat of combustion
- Thermochemistry and calorimetry
- Experimental design
- Quantitative analysis
Setup and safety notes
- Use aluminium beverage cans. If the can has no tab, punch two small holes near the top rim to pass the stirring rod through.
- Start with the water between 10 and 15 °C, and make sure no ice is left unmelted in the beaker.
- Alcohol flames are nearly invisible: tell students what to look for before lighting, and work in a well-ventilated area.
- Extension for advanced courses: calculate the heat of combustion in kJ/mol using the molar masses from the pre-lab work.
Equipment: Go Direct® Temperature Probe and Vernier Graphical Analysis.
Experiment 3 · Arson: identifying the accelerant by gas chromatography
The case: a series of suspicious barn fires. Students receive an unidentified accelerant sample and have to determine what it is made of.
The work happens in two stages. First the class builds its own library of chromatograms by running known compounds and recording their retention times. Then it injects the unknown sample and compares. What is pedagogically interesting is that students are not handed a reference table: they build it, and in the process they have to explain why one compound takes longer than another to leave the column — which is, at bottom, a question about intermolecular forces.
Concepts covered
- Gas chromatography
- Retention time analysis
- Intermolecular forces
- Molecular properties
- Separation science
Randy Booth, who teaches at Itineris Early College High School (Utah), notes that this lab runs unchanged from secondary school through the first courses of general university chemistry: it is the same instrument and the same analysis, with a different level of rigour expected in the interpretation.
Looking after the instrument
- Power the Mini GC at least 5 minutes before using it, and let it return to room temperature before switching it off.
- Do not pull the syringe plunger back past 0.6 µL: the wire can come out of the needle.
- Use reagent-grade compounds. Water damages the instrument, and store-bought isopropyl alcohol can contain between 9 % and 30 % water.
Equipment: Go Direct® Mini GC™ and Vernier Instrumental Analysis.
The equipment for all three experiments
A lab that already works with Go Direct® pH and temperature sensors can run the first two experiments without buying anything else; the third one needs the Mini GC™. Below is each component with its page in the regional store, where prices for Chile are listed.
Go Direct® Sensor de pH
Measures pH in real time during the makeup remover titration. It is the one sensor experiment 1 cannot do without.
See it on TecnologíasEducativas.cl ↗
Go Direct® Contador de Gotas
Counts and records titrant volume drop by drop, which is what makes the first- and second-derivative analysis possible in advanced courses.
See it on TecnologíasEducativas.cl ↗
Go Direct® Sensor de Temperatura
Records the water temperature change in the accelerant calorimetry of experiment 2.
See it on TecnologíasEducativas.cl ↗
Go Direct® Mini GC™
Benchtop gas chromatograph that runs on room air, with no carrier gas tank. It is the instrument behind experiment 3.
See it on TecnologíasEducativas.cl ↗
Vernier Graphical Analysis™
Free data-collection and analysis app for experiments 1 and 2; the Pro edition adds curve fitting and video analysis.
See it on TecnologíasEducativas.cl ↗
Vernier Instrumental Analysis™
Software that drives the Mini GC and displays the chromatograms with their retention times.
See it on TecnologíasEducativas.cl ↗
Forense con Vernier
Lab book with Vernier's forensic investigations, teacher guidance and electronic files for the course.
See it on TecnologíasEducativas.cl ↗Districalc: forensic chemistry for schools and universities across Latin America
Districalc is an authorised Vernier distributor operating in more than 20 Latin American countries since 1981. We supply the Go Direct® sensors, the Mini GC™ and the lab books, and we back the rollout with teacher training and local technical support.
You can browse the full chemistry catalogue to see the rest of the Vernier ecosystem —spectrophotometry, electrochemistry, conductivity— and the teacher training page for the professional development that comes with every rollout.
Is your institution planning a forensic chemistry unit this year? Write to us: we put together the equipment list according to the level of the course and the experiments you want to cover.
To go deeper: Vernier's original article on three forensic chemistry experiments, the page for the Forensic Chemistry Experiments lab book, and the forensics lab book on TecnologíasEducativas.cl.
Ready to build your forensic chemistry unit?
Districalc supplies the Vernier sensors, the lab books, the teacher training and the technical support to put these experiments into your chemistry curriculum — in any Latin American country.
Contact UsFrequently asked questions
Which forensic chemistry experiments can be run in a school lab?
Three investigations cover a good share of the curriculum: an acid-base titration to determine how much sodium hydroxide was added to a tampered makeup remover, a combustion calorimetry to compare accelerants from a fire, and a gas chromatography analysis to identify an unknown accelerant. All three come from Vernier's Forensic Chemistry Experiments lab book and work from high school through introductory college chemistry.
Which sensors are needed for the tampered makeup remover titration?
The Go Direct pH Sensor is essential. The Go Direct Drop Counter is optional and gets added when you want the first- and second-derivative analysis in advanced courses. Data is collected with Vernier Graphical Analysis, which is free. In a secondary course the pH sensor alone is enough.
How is the same forensic lab adapted to different levels?
At secondary level the equations are provided ready-made and students work with the pH sensor alone. In science-track courses the full lab is kept but the derivative analysis is left out. At pre-university or first-year university level the full dilution calculation, the drop counter setup and the first- and second-derivative analysis are all included. The base procedure does not change: what changes is how much is asked of the student.
What precautions does the accelerant calorimetry experiment require?
Work in a well-ventilated area and warn students that alcohol flames are nearly invisible, so they know what to look for before lighting. The water should start between 10 and 15 °C, with no ice left unmelted. If the aluminium can has no tab, punch two small holes near the top rim to pass the stirring rod through.
What care does the Go Direct Mini GC need in the arson analysis?
It has to be powered at least 5 minutes before use and allowed to return to room temperature before being switched off. The syringe plunger must not be pulled back past 0.6 µL, or the wire can come out of the needle. And only reagent-grade compounds should be used: water damages the instrument, and store-bought isopropyl alcohol can contain between 9 % and 30 % water.