Year 8 Science · Unit 1 · Lesson 4
Challenge Worksheet
Learning Goals
Design a mini-experiment
A scientist wants to test: "Does the number of leaves on a shoot affect the rate of water uptake?" Plan the investigation below. Remember: a good experiment changes only one thing at a time.
Background
Leaves carry out transpiration, they lose water vapour through their stomata. This loss of water "pulls" more water up through the xylem from the roots. If leaves drive water uptake, then the number of leaves on a shoot might affect how fast water moves up the stem. You will use fresh leafy shoots (such as celery or geranium) placed in water, and measure how much water disappears over time.
| 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 (use the word "because") | |
| How I would know if my prediction is wrong | |
| One limitation of this experiment |
1. A student removes all the leaves from one shoot and keeps 10 leaves on a second shoot. After one hour, the leafless shoot has taken up 2 mL of water, and the leafy shoot has taken up 18 mL. Explain this difference using what you know about stomata, transpiration and the role of leaves in the plant's vascular system.
2. Suggest one way to improve this experiment so that the results would be more reliable. Explain why your improvement helps.
Wrap Up
In one sentence, what was the main idea of this lesson?