A student conducts an experiment to determine how the temperature of water affects the time for sugar to dissolve. In each trial, the student uses a different amount of water and a different temperature of water.

What is wrong with this experimental design?

The student does not have a dependent variable.

The student needs to perform more trials.

The student did not change enough independent variables.

The student changed more than one independent variable.

An experiment is a procedural method of solving a scientific problem or answering a scientific question. An ideal experiment should contain two variables namely: independent variable and dependent variable.
Dependent variable: This is the variable that the experimenter measures in the experiment. The dependent variable responds to changes made to the independent variable.
Independent variable: This is the variable that is manipulated in an experiment in order to bring about a response.

In the experiment conducted by the student in this question in order to determine how the temperature of water affects the time for sugar to dissolve. The independent variable is the DIFFERENT TEMPERATURE OF WATER while the dependent variable is the TIME TAKEN FOR SUGAR TO DISSOLVE.

N.B: An experiment should have only one independent variable and all other variables should be kept constant. This is to have a reliable result.

However, this student used two independent variables (temperature and amount of water) for the experiment, which is wrong for the experimental design.

Therefore, the fact that the student changed more than one independent variable is wrong for the experimental design.