Chandani wanted to investigate the effects of substances mixed with the soil on plant growth. She decided to mix lime, urea fertilizer, common salt, and compost manure in the soil. Then she brought a bucket of soil from a nearby field and sieved it. She put that soil equally into 12 uniform-sized pots. Then she mixed two spoons of salt in every three pots, two spoons of urea fertilizer in each of the next three pots, two spoons of table salt in each of the next three pots and finally, two spoons of compost fertilizer in each of the remaining three pots. She then planted similar seeds of the same plant in every pot and placed them all in a sunny place in the house. She watered all the pots every day. After the plants grew, she measured the height of each plant daily and kept a record.
i) Identify the independent variable, the dependent variable and controlled variable in Chandani's experiment.
ii) Why did Chandani use 3 pots for each experiment?

Question

Chandani wanted to investigate the effects of substances mixed with the soil on plant growth. She decided to mix lime, urea fertilizer, common salt, and compost manure in the soil. Then she brought a bucket of soil from a nearby field and sieved it. She put that soil equally into 12 uniform-sized pots. Then she mixed two spoons of salt in every three pots, two spoons of urea fertilizer in each of the next three pots, two spoons of table salt in each of the next three pots and finally, two spoons of compost fertilizer in each of the remaining three pots. She then planted similar seeds of the same plant in every pot and placed them all in a sunny place in the house. She watered all the pots every day. After the plants grew, she measured the height of each plant daily and kept a record.

i) Identify the independent variable, the dependent variable and controlled variable in Chandani's experiment.

ii) Why did Chandani use 3 pots for each experiment?

Atith Adhikari · Accepted Answer

Chandani's experiment has all three variables of scientific research. We have identified them and noted below:

Independent Variable: Amount of substances mixed into the soil, including lime, urea fertilizer, common salt, and compost manure
Dependent Variable: Height of plant
Controlled Variable: Seeds of the plant, Quantity of Soil, Amount of sunlight, Water received by the plant

By using three pots for her experiment, Chandani minimizes error and eliminates anomalies. If it is true that the amount of substances mixed into the soil affects the growth (in height) of the plant, the seeds placed in the three pots containing the same amount of substances must experience similar growth.

This factor increases the validity of the outcomes of the experiment.