Year 7 Science · Unit 2 · Lesson 10
Challenge Worksheet
Learning Goals
Design a mini-experiment
A scientist wants to test: "Does particle size affect the rate at which antacid tablets dissolve in water?" Plan the investigation below.
| What I will change (independent variable) | |
| What I will keep the same (controlled variables, list at least 3) | |
| What I will measure (dependent variable) | |
| My prediction (what I expect to happen and why, using particle ideas) | |
| How I would know if my prediction is wrong | |
| One limitation of this experiment |
1. After carrying out the antacid experiment, a student finds that the powdered tablet dissolved in 18 seconds and the whole tablet dissolved in 95 seconds, but both left the same clear solution with no undissolved solid. Explain these results using the concepts of surface area, rate, and maximum solubility.
2. A student plans to test particle size but accidentally uses warm water (40°C) for the powdered tablet and cold water (18°C) for the whole tablet. Explain what is wrong with this experimental design and predict how it would affect the student's conclusion about particle size.
Wrap Up
In one sentence, what was the main idea of this lesson?