Choose a method, control variables and use evidence from graphs.
| English | Chinese |
|---|---|
| control variable | 控制变量 |
| mass loss | 质量损失 |
| end point | 终点 |
| tangent | 切线 |
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Give one limitation of the gas-syringe method and a specific improvement.
Identify the variable, measurement and control first. Distinguish mass remaining from mass lost.
Gas may escape before sealing; use a sealed arrangement that allows mixing after sealing, or minimise and standardise the delay. Check connections for leaks.
The mass falls from 120.50 to 120.02 g in 60 s. Find the average mass-loss rate.
Subtract final mass from initial mass, then divide by time.
Mass lost = 0.48 g. Rate = 0.48 ÷ 60 = 0.0080 g s⁻¹.
Two cross experiments take 80 s and 40 s at the same endpoint. Compare relative rates.
For the same endpoint, compare 1/time.
1/40 is twice 1/80, so the 40 s experiment has twice the relative rate.
Use Lesson 4 in your worksheet for written practice. Your teacher will discuss those answers in class.