Weigh a sample, heat it, and reweigh it to find out how much of a compound is made of each element — then check your math against the real formula.
Balance & Burner
DIGITAL BALANCE-- . -- g
Ready to begin. Place the empty container on the balance.
Data & Calculations
Trial History
Trial
Container (g)
+ Initial (g)
+ Final (g)
% A
% B
% Error
No completed trials yet. Finish a worksheet and check your work to log a trial here.
Teacher notes
Each student (or each "new trial") gets randomized masses and a small amount of built-in experimental error, so results are never identical and percent-error discussion is always meaningful.
The worksheet checks numeric answers within a tolerance of about ±0.3 percentage points, so reasonable rounding is accepted.
"Show correct values" is disabled until a student has attempted a check, to discourage skipping the calculation.
Use "Print lab report" for a clean, gradable printout of the data table, worksheet, and trial history with the apparatus and buttons hidden.
Two experiments are included: synthesis of magnesium oxide (mass gain) and dehydration of a copper sulfate hydrate (mass loss) — together they cover both directions of percent-composition-by-mass reasoning.
This file is a single self-contained HTML page with no external dependencies or network calls, so it should run unmodified inside most LMS or classroom-tool embeds.
A printable "Certificate of Achievement" unlocks the first time a student's worksheet checks out fully correct, and updates automatically if they go on to complete the second experiment too. Students type their own name before printing — nothing is submitted or saved anywhere.