Experiment 4

Are small amounts of soap or detergent harmful to the growth of plants?


  • Radish or beet seeds
  • Soap and detergent
  • 3 Styrofoam cups
  • Soil
  • Water
  • 2 Quart jars

Do this first:

This is a picture of sproutsFill the jars to the same levels with water, and then make soap and detergent solutions. For one jar use 1/4 teaspoon detergent and fill with water. For the other, use 1/4 teaspoon soap and fill with water.

1.Plant 2 seeds in each cup, about 1-cm deep, and place in a sunny windowsill.

2. Water one cup with 2 tablespoons of soap solution every day.

3. Water a second cup with 2 tablespoons of detergent solution every day.

4. Water the remaining cup with 2 tablespoons of tap water every day.

5. Chart the growth of plants in each cup. Compare the results. Which sprouts first? Which grows fastest?


What happens to soap when it leaves your bathtub?