The variables

As from the previous post, the next question is to write the variables involved.

In this question, you are requested to give the responding variable of the experiment..
Clue: Observe the diagram given.. what had changed??

From the diagram you'll see that it was the gas volume that's different for each measuring cylinder.

So, it must be the volume of the gas (hydrogen) is the responding variable, don't you think?

Correct!!

The answer is: "The volume of the gas produced"

OR

You can also refer to the statement, "...to study the reactivity of metal..." at the beginning of the question above... This statement shows the AIM of the experiment.

What are we going to study? The reactivity of metals... So, the reactivity of metals should be the responding variable.
To answer, just COPY that statement back!  ---> "The reactivity of metals" in the answer area. You'll get correct answer!

Extensions:

Which, do you think are the

• manipulated variable? (Clue: look back at the beginning of this question)

Can you see the statement, "...to study the reactivity of metal P, Q and R..."?
In this experiment, we used three types of metal, right? Which means, we manipulate the type of metals used for the experiment.. so, that IS the manipulated variable.

To answer this question, just write "The types of metal" in the answer area.
OR just copy "Metal P, Q and R" from the statement...

•  Constant variable? (clue: Look at the statement AGAIN!)

Can you see the "...when reacts with water within 5 minutes."?
In this experiment, we fix the time of reaction to 5 minutes only, not 10, not 20.  All three measuring cylinders undergo the SAME time duration. It means, we made the time remain CONSTANT along the experiment, this is the constant variable.

To answer, just write "Time of experiment" in the answer line. That's all!