ES HWK 12.2.16 - Identifying Variables Worksheet - Free Printable

Let's go through each of the four experimental scenarios and identify the independent variable, dependent variable, and control variable for each.

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1) Different rose bushes are grown in a greenhouse for two months. The number of flowers on each bush is counted at the end of the experiment.

- a. Independent Variable: *Type of rose bush*
(This is what is being changed or tested — different types of rose bushes.)

- b. Dependent Variable: *Number of flowers on each bush*
(This is what is being measured or observed as a result of the independent variable.)

- c. Control Variable: *Growing conditions (light, temperature, water, soil type, etc.) in the greenhouse*
(These factors are kept constant to ensure that only the type of rose bush affects the outcome.)

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2) You water three sunflower plants with salt water. Each plant receives a different concentration of salt solutions. A fourth plant receives pure water. After a two-week period, the height is measured.

- a. Independent Variable: *Concentration of salt solution*
(The amount of salt in the water varies among the plants.)

- b. Dependent Variable: *Height of the sunflower plants*
(This is what is being measured after the treatment.)

- c. Control Variable: *Amount of water given, light exposure, soil type, pot size, temperature, and time period*
(All these are kept the same except for the salt concentration. The fourth plant with pure water serves as the control group.)

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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.

- a. Independent Variable: *Humidity level*
(Different humidity levels are applied to the trees.)

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

- c. Control Variable: *Light, temperature, soil, watering schedule, type of tree, time period, and location (except for the one outside)*
(These should be kept constant. The tree outside serves as a control group under natural conditions.)

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4) Pea plant clones are given different amounts of water for a three-week period. The first pea plant receives 400 milliliters a day. The second receives 200 milliliters a day. The third receives 100 milliliters a day. The fourth receives no extra water (only natural sources). The height of pea plants is recorded daily.

- a. Independent Variable: *Amount of water given per day*
(This is varied: 400 mL, 200 mL, 100 mL, and none.)

- b. Dependent Variable: *Height of the pea plants*
(This is measured daily to observe growth response.)

- c. Control Variable: *Type of plant (clones), light exposure, soil type, container size, temperature, and time period*
(These are kept constant so that only water amount affects growth. The fourth plant (no extra water) acts as the control group.)

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✔ Summary Table:

| Scenario | Independent Variable | Dependent Variable | Control Variable |
|--------|----------------------|--------------------|------------------|
| 1 | Type of rose bush | Number of flowers | Light, temperature, water, soil, etc. |
| 2 | Salt concentration in water | Height of sunflower | Water volume, light, soil, pot size, etc. |
| 3 | Humidity level | Height of redwood tree | Light, temperature, soil, watering, etc. |
| 4 | Amount of water per day | Height of pea plant | Plant type, light, soil, temperature, etc. |

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💡 Key Definitions Recap:
- Independent Variable: What you change.
- Dependent Variable: What you measure.
- Control Variable: What you keep the same.

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