Experimental variables worksheet - Name: Date: - Studocu - Free Printable

Problem: Identify the Independent Variable (IV), Dependent Variable (DV), Constants, and Control for each of the given science experiments.

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

1. Independent Variable (IV):
- The breeds of bushes are the independent variable because they are the factor being changed or varied in the experiment.

2. Dependent Variable (DV):
- The number of flowers is the dependent variable because it is what is being measured and is expected to change based on the type of bush.

3. Constants:
- Environmental conditions in the greenhouse: Factors such as temperature, light, humidity, and soil quality should be kept constant to ensure that any changes in the number of flowers are due to the breed of the bush and not other variables.
- Time period: The recording is done weekly over two months, so the time interval is consistent.
- Watering schedule: All bushes should receive the same amount and frequency of watering.
- Fertilization: All bushes should receive the same type and amount of fertilizer (if used).

4. Control:
- There is no explicit control mentioned in this experiment. However, if one breed of bush is chosen as a standard for comparison, it could serve as a control. For example, if one breed is known to have a typical flowering pattern, its performance could be compared to the others.

---

#### Experiment 2:
Description: 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.

1. Independent Variable (IV):
- The type of watering solution (pure water vs. different concentrations of salt solutions) is the independent variable because it is the factor being manipulated.

2. Dependent Variable (DV):
- The height of the sunflowers is the dependent variable because it is what is being measured and is expected to change based on the type of watering solution.

3. Constants:
- Sunlight exposure: All sunflowers should receive the same amount of sunlight.
- Soil type and quality: The soil should be the same for all sunflowers.
- Amount of water: If using different concentrations of salt solutions, the total volume of water given to each plant should be the same.
- Temperature and humidity: These environmental factors should be kept constant.
- Age and initial size of sunflowers: All sunflowers should start at the same age and size.

4. Control:
- The sunflowers watered with pure water serve as the control group. Their growth will be compared to the sunflowers watered with salt solutions to determine the effect of the salt concentration.

---

#### Experiment 3:
Description: 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.

1. Independent Variable (IV):
- The humidity levels inside the greenhouse are the independent variable because they are the factor being changed.

2. Dependent Variable (DV):
- The height of the trees is the dependent variable because it is what is being measured and is expected to change based on the humidity levels.

3. Constants:
- Light exposure: All trees should receive the same amount of light.
- Temperature: The temperature inside the greenhouse should be controlled and consistent for the trees under different humidity levels.
- Watering schedule: All trees should receive the same amount and frequency of watering.
- Soil type and quality: The soil should be the same for all trees.
- Initial size and age of trees: All trees should start at the same age and size.

4. Control:
- The tree left outside in normal conditions serves as the control. Its growth will be compared to the trees grown under different humidity levels to determine the effect of humidity on tree height.

---

Summary of Answers:

#### Experiment 1:
- IV: Breeds of bushes
- DV: Number of flowers
- Constants: Environmental conditions, watering schedule, fertilization, time period
- Control: None explicitly stated; could be a standard breed for comparison

#### Experiment 2:
- IV: Type of watering solution (pure water vs. salt solutions)
- DV: Height of sunflowers
- Constants: Sunlight, soil type, amount of water, temperature, humidity, age/size of sunflowers
- Control: Sunflowers watered with pure water

#### Experiment 3:
- IV: Humidity levels
- DV: Height of trees
- Constants: Light exposure, temperature, watering schedule, soil type, initial size/age of trees
- Control: Tree left outside in normal conditions

---

Final Answer:

\boxed{
\begin{array}{l}
\text{Experiment 1:} \\
\text{IV: Breeds of bushes} \\
\text{DV: Number of flowers} \\
\text{Constants: Environmental conditions, watering schedule, fertilization, time period} \\
\text{Control: None explicitly stated; could be a standard breed for comparison} \\
\\
\text{Experiment 2:} \\
\text{IV: Type of watering solution (pure water vs. salt solutions)} \\
\text{DV: Height of sunflowers} \\
\text{Constants: Sunlight, soil type, amount of water, temperature, humidity, age/size of sunflowers} \\
\text{Control: Sunflowers watered with pure water} \\
\\
\text{Experiment 3:} \\
\text{IV: Humidity levels} \\
\text{DV: Height of trees} \\
\text{Constants: Light exposure, temperature, watering schedule, soil type, initial size/age of trees} \\
\text{Control: Tree left outside in normal conditions}
\end{array}
}