The fact that the student used different amount of water (another independent variable) is wrong with the experimental design
WHAT ARE THE COMPONENTS OF AN EXPERIMENT?
An experiment aims at solving a scientific problem or answering a scientific question. An experiment should contain a variable being changed called INDEPENDENT VARIABLE and a variable being measured called DEPENDENT VARIABLE.
In an ideal experiment, only one independent variable should be used while every other variable should be kept constant. This is done so as not to affect the result of the experiment.
In the experiment conducted by the student in this question, two independent variables were used i.e. the differentamount of water and the differenttemperatures. This is what is wrong about the experimentaldesign.
In a nutshell, the fact that two independent variables were used by the student is what is wrong about the experimentaldesign.
