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The materials required for this science fair project:
- 15 potted radish plants of almost the same height
- distilled water
- tap water
- recycled water
- a ruler
- a black marker pen


1. For this science fair project, the independent variable is the type of water used to water the plants – distilled water, tap water and recycled water. The dependent variable is the height of the radish plants. This is determined by measuring the height of the radish plant every week. The constants (control variables) are the size of the pot, the original size of the plant, the type of plant, the amount of water given to each plant and the amount of sunlight received.

2.  Fifteen radish plants are separated into 3 groups of 5 pots each. The average height of the plants is obtained by totaling the height of the plants in each group and dividing by 5. The average height is calculated and recorded in the table below.

3. The pots in each group are labeled as “distilled”, “tap” and “recycled” using the black marker pen in order to differentiate between the 3 groups.

4. The 15 pots are placed in a location where they are able to receive the same amount of sunlight. They are watered once a day with the same amount of water. The group of pots labeled “distilled” is watered with distilled water only. The pots labeled “tap” are watered with tap water only and the pots labeled “recycled” are watered with recycled water only.

5. The height of the plants is measured once every week for the next 4 weeks. The average height for each group of plants is obtained by totaling the height and dividing by 5. The calculated average is recorded in the table given below.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 28 days for the science project experiment
Material availability:
You will need access to a source of recycled water.
Safety concerns:

Basic safety requirements