Reaction rates · Grade 10
The disappearing cross
ChemAI · Worksheet
NameClassDate
Aim
How does concentration change the time for sulfur to hide the X?
⚠ Sulfur dioxide is released: work in a well-ventilated room.
Before you start: what do you predict will happen? Why?
What you do
| Step | What I observed | |
|---|---|---|
| 1 | Add 5 mL of hydrochloric acid to beaker 1. Tip: set the speed to ×5. | |
| 2 | Add 5 mL of hydrochloric acid to beaker 2 (half the thiosulfate concentration). | |
| 3 | Wait until the X disappears in both beakers and compare the times. |
Questions
- Write a word or symbol equation for one reaction you observed.
- Explain your most important observation using particles, ions or energy.
- Was your prediction right? What would you change to get a more reliable result?