Final answer:
In a controlled experiment with plants, variables such as pot size and water amount are kept constant to isolate the effect of the tested variable. Factors like sunlight, soil temperature, and water loss are potential confounding factors that need to be controlled. The experiment's objective would be to observe the impact of a single variable, such as the presence of detergent in soil on plant growth.
Step-by-step explanation:
Scientific Experiments with Plants
When conducting scientific experiments with plants such as measuring their growth in response to different conditions, it is crucial to control certain variables to isolate the effects of the variable of interest. In such a controlled experiment, plants might be grown in the same type and size of pots to ensure that container size does not impact growth variability. Additionally, providing the same amount of water to all plants isolates other variables such as light or nutrients that might be tested. In an experiment that aims to determine how a factor like detergent in the soil affects plant growth, both a control group (without detergent) and a test group (with detergent) should be present to compare the outcomes.
Common issues that can arise in experiments involve uncontrolled variables such as sunlight in Gary's case where pots are placed in sun and shade, which affects the confidence in attributing differences in growth to the presence of detergent only. Similarly, factors such as soil temperature, water loss due to evaporation, and the effect of insects could all be potential uncontrolled variables that might influence the outcome of an experiment if not properly managed.
In summary, a properly designed controlled experiment in a laboratory setting involves meticulous planning to ensure that all variables, except the one being tested, are kept constant.