Answer:
By isolating one variable at a time, Zach can draw more accurate conclusions about the relationship between the variable and the reaction rate. This helps to ensure that any observed changes are due to the variable being tested, rather than being influenced by other factors.
Step-by-step explanation:
The problem with Zach's experimental design is that there are two variables in each trial (option C).
In an experiment, it is important to have only one variable changing at a time in order to determine its specific effect on the outcome. This is known as controlling variables. In Zach's experiment, he is changing both the form of magnesium (ribbon, coil, slivers) and the concentration of the hydrochloric acid (1.0 M, 2.0 M, 3.0 M) in each trial. This means that it is unclear which variable is responsible for any observed changes in the reaction rate.
To improve the experimental design, Zach should only change one variable at a time while keeping all other conditions constant. For example, he could run separate trials where he keeps the magnesium form constant (e.g., ribbon) and changes only the concentration of the hydrochloric acid. This would allow him to observe and compare the effect of acid concentration on the reaction rate while controlling for other factors.
By isolating one variable at a time, Zach can draw more accurate conclusions about the relationship between the variable and the reaction rate. This helps to ensure that any observed changes are due to the variable being tested, rather than being influenced by other factors.