Experimental Variables Worksheet | PDF | Experiment | Nature - Free Printable

Let's solve each of the three experimental scenarios on the Experimental Variables Worksheet by identifying the Independent Variable (IV), Dependent Variable (DV), Constants, and Control.

---

1) The number of flowers on different breeds of bushes in a greenhouse is recorded every week for two months.

- IV (Independent Variable):
*Different breeds of bushes*
→ The experimenter is changing the type of bush (breed), so this is what is being manipulated.

- DV (Dependent Variable):
*Number of flowers*
→ This is what is being measured or observed over time.

- Constants:
- Greenhouse environment (temperature, light, soil type, watering schedule, etc.)
- Time interval (recorded weekly)
- Duration of the experiment (two months)
→ These factors are kept consistent across all bushes to ensure fair comparison.

- Control:
*None explicitly stated as a control group.*
→ However, if one breed is considered "standard" or used as a baseline for comparison, it could serve as a control. But since no specific control is mentioned, we might say:
→ *There is no clear control group; all breeds are being compared against each other.*

> ✔ Answer Summary:
> - IV: Breed of bush
> - DV: Number of flowers
> - Constants: Greenhouse conditions, watering, light, soil, recording frequency
> - Control: None specified (all groups are experimental)

---

2) You give four sunflowers different watering with either pure water or different concentrations of salt solutions. After a two-week period, the height is measured.

- IV (Independent Variable):
*Type of water given (pure water vs. different salt concentrations)*
→ The experimenter is changing the water type/salt concentration.

- DV (Dependent Variable):
*Height of the sunflowers*
→ This is what is being measured after two weeks.

- Constants:
- Type of sunflower (same species)
- Amount of water given (if equal volumes)
- Pot size, soil type, sunlight exposure, temperature, duration of experiment (2 weeks)
→ All factors except water type must be kept constant.

- Control:
*Sunflower watered with pure water*
→ This group serves as the baseline to compare against the salt-treated plants.

> ✔ Answer Summary:
> - IV: Concentration of salt in water (or type of water)
> - DV: Height of sunflowers
> - Constants: Sunflower type, pot size, soil, light, temperature, amount of water, time
> - Control: Sunflower(s) receiving pure water

---

3) Three redwood trees are kept at different humidity levels inside a greenhouse for 12 weeks. One tree is left outside in normal conditions. Height of the tree is measured once a week.

- IV (Independent Variable):
*Humidity level*
→ The experimenter is varying the humidity inside the greenhouse.

- DV (Dependent Variable):
*Height of the tree*
→ Measured weekly to see how growth changes with humidity.

- Constants:
- Type of tree (redwood)
- Light exposure (assuming similar lighting)
- Soil type and amount
- Watering schedule
- Measurement frequency (once per week)
- Duration (12 weeks)
→ These should remain unchanged across all trees.

- Control:
*The tree left outside in normal conditions*
→ This tree is not exposed to controlled humidity levels and represents natural conditions, providing a baseline for comparison.

> ✔ Answer Summary:
> - IV: Humidity level
> - DV: Height of the tree
> - Constants: Tree species, soil, light, water, measurement timing, duration
> - Control: Tree left outside in normal conditions

---

✔ Final Answers:

#### 1)
- IV: Breed of bush
- DV: Number of flowers
- Constants: Greenhouse conditions, watering, light, soil, recording frequency
- Control: None specified

#### 2)
- IV: Type of water (pure water vs. salt solutions)
- DV: Height of sunflowers
- Constants: Sunflower type, pot size, soil, light, temperature, water volume, time
- Control: Sunflower watered with pure water

#### 3)
- IV: Humidity level
- DV: Height of the tree
- Constants: Tree species, soil, light, water, measurement frequency, duration
- Control: Tree left outside in normal conditions

---

This worksheet helps students understand how to identify key components of an experiment, which is essential for designing valid scientific investigations.