Balancing Chemical Equations Simulation

In a chemical reaction atoms are never created or destroyed, only rearranged. That is why every equation has to balance: each element needs exactly as many atoms on the right as on the left. You balance an equation by changing the coefficients, the big numbers in front of the formulas, which count how many molecules there are. The small subscripts inside a formula are fixed, because changing one would make a different substance. Once every element matches, check that the numbers are the smallest whole numbers that work. 2H₂ + O₂ → 2H₂O has four hydrogen and two oxygen atoms on both sides, while H₂ + O₂ → H₂O has two oxygen atoms going in and only one coming out, and an atom cannot simply vanish. Because atoms are conserved, mass is conserved too. Students can change number of h₂ and number of o₂ and compare what happens. Use it for chemistry inquiry with Middle School and High School on a projector or student device.

Standards: NGSS MS-PS1-5, HS-PS1-7

• Balance H₂ + O₂ → H₂O and watch the oxygen scale level out
• Change one coefficient to fix an element and see what it does to the others
• Double every number in a balanced equation and see why it is flagged as not the smallest
• Work up from the warm-up equations to burning propane, C₃H₈ + O₂ → CO₂ + H₂O
• Drag the spotlight lens onto an atom to count one element across the whole equation

1. 1Predict how changing number of h₂ will affect the hydrogen atoms in, then test the prediction.
2. 2Use evidence from the interactive visual to explain the result.

Questions teachers ask