Question

a chemist is study the effects of minerals on plant growth. She knows that phosphorus stimulates pant growth. She decides to test the effects of various phosphorus concentration on plants every 5 days over a 20 day period what is the independent variable?

Answer 1

independent variable is what you will change in an experiment.
therefore, the independent variable should be the concentration of phosphorus every 5 days
because she wanted to know how different concentration affects the plant growth