Scientific method variables (worksheet) | PDF - Free Printable

Here’s the solution to the questions based on the diagram:

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1. According to the diagram, which question is being tested?

✔ Correct Answer: c. Does adding fertilizer cause flowering plants to grow taller?

Explanation:
The diagram shows two identical potted flowering plants. Both receive 200 mL of water. The only difference is that one plant receives 10 mL of fertilizer, while the other does not. This setup is a classic controlled experiment designed to test the effect of one variable — fertilizer — on plant growth (specifically height, as implied by the question).

- Option a (salt water) — not mentioned or shown.
- Option b (how much fertilizer plants need) — this would require testing multiple amounts; here, only one amount is used.
- Option d (best kind of fertilizer) — this would require testing different types of fertilizers; only one type is shown.

So, the experiment tests whether adding fertilizer causes plants to grow taller — making c the correct answer.

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2. Write change in the blank beside the change variable; responding beside the responding variable; and control beside any control variables.

✔ a. the size of the pot → control

✔ b. the kind of potting soil → control

Explanation:

In a scientific experiment:
- Change variable (independent variable) = what you deliberately change to test its effect → In this case, it’s whether or not fertilizer is added. (This isn’t listed in parts a or b, so we don’t assign “change” to either.)
- Responding variable (dependent variable) = what you measure or observe as a result → Here, it’s plant height (again, not listed in a or b).
- Control variables = factors kept the same to ensure a fair test → These include:
- Size of the pot (both pots look identical)
- Kind of potting soil (assumed same unless stated otherwise)
- Amount of water (200 mL each)
- Type of plant
- Light, temperature, etc. (implied to be same)

Since both a. the size of the pot and b. the kind of potting soil are kept constant to avoid affecting the outcome, they are control variables.

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✔ Final Answers:

1. c. Does adding fertilizer cause flowering plants to grow taller?

2.
- a. the size of the pot → control
- b. the kind of potting soil → control

*(Note: The actual “change variable” — fertilizer — and “responding variable” — plant height — are not listed in parts a and b, so no “change” or “responding” labels are assigned to those blanks.)*