Year 7 Science · Unit 2 · Lesson 17
Challenge Worksheet
Learning Goals
Design a mini-experiment
A scientist wants to test: "Does temperature affect how much sugar can dissolve in 100 mL of 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) | |
| How I would know if my prediction is wrong | |
| One limitation of this experiment |
1. A student conducts the experiment above and finds that at 80°C, about 360 g of sugar dissolves in 100 mL of water, but at 20°C only about 204 g dissolves. When the 80°C solution cools back to 20°C in a sealed container, crystals begin to form at the bottom. Using the terms saturated and solubility, explain why this happens.
2. The scientist wants to make the experiment more reliable. She decides to repeat each temperature level three times and take an average. Explain why repeating trials and averaging results improves the reliability of the data. What could cause the three trials to give slightly different results even when the procedure is followed carefully?
Wrap Up
In one sentence, what was the main idea of this lesson?