homework help pls...science graph...which is the independant variable?

10
Found 19th Sep 2010
Hi
I know this will be easy peasy to some of you science maths students.
My son missed a lesson and has to draw a graph which he has never done before, he's 11.
He has the figures for volume of acid and time of reaction.
Can i clarify which is the independant variable please as he has been told this goes on the x axis.
Are we right in thinking its the time of reaction.
Wow hope he never asks me another science question otherwise I may have to have a hotline to HUKD.

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As above the independant variable is the one that the user controls, so must be the volume of acid.


The independent variable are changes that occur in an experiment that are directly caused by the experimenter in this case this would be the volume of acid as it can be changed by the person doing it. Hope this helps!!

Original Poster

thanks thats what he did originally but his graph seems to be strange. He has been told to do a straight line from zero...
I understand doing a straight line through the middle of the coordinates but my son thinks it goes from (0,0) and his line runs top left downwards if that makes sense.
he was expecting it to run bottom left upwards.

In that case he has probably got the titles for the axis the wrong way around. Was he sure that he was told to put the independant on the x axis?? usually the other way around......

Original Poster

emmaelise...i bet that is the problem he says he was told to put it on the x but it was his first time doing graphs so easy to get muddled. That would certainly make the graph look the way he had expected.

Would appreciate someone else confirming as well please
Should we have time of reaction on the bottom and volume up the side.
Thanks

Usually you would have the volume up the side and time of reaction along the bottom axis, maybe if he is unsure he can draw it both ways and show the teacher he has done his best.

or you could use 1/time instead of time

EDIT: Actually for this type of exp, probably best to switch the axes.
Time is usually kept on the x-axis; however usually the independant var is always on the x-axis also.
Therefore, switch the axes
Edited by: "amzmalhotra" 19th Sep 2010

You need to know what the actual experiment is to say which is the independent value: is it measuring the change in volume of acid over time as a reaction takes place, or measuring the time taken for a reaction at different volumes of acid? That information isn't in the OP so its not possible to say definitely one way or the other.

I'd have thought that the independent value is the time of reaction - the volume of acid depends on the time. In this case, the time will be on the x-axis, the volume on the Y. The resultant line should go from time=0, but that doesn't mean it has to pass through the origin of the graph (0,0)...

mumbojumbo

The independent variable is the object that the user can change/vary - … The independent variable is the object that the user can change/vary - I'm guessing it's the volume of acid in this experiment.


kidcat

As above the independant variable is the one that the user controls, so … As above the independant variable is the one that the user controls, so must be the volume of acid.


emmaelise

The independent variable are changes that occur in an experiment that are … The independent variable are changes that occur in an experiment that are directly caused by the experimenter in this case this would be the volume of acid as it can be changed by the person doing it. Hope this helps!!



My guess is the experimenter is observing the volume of acid that is present in a reaction as time passes, as opposed to changing the volume of acid and measuring time. In this case, time would therefore be the independant value; time=0 is when the reaction starts, as time passes the volume of acid will change...

If however, its an experiment in which different volumes of acid are used and the time it takes to create a reaction is measured, the time will be on the y-axis and the volume on the x, but I would have thought the former is more likely....






Edited by: "jah128" 19th Sep 2010

The independent variable is the one changed by the experimenter. In this case, it's the volume of acid and it goes on the x axis.

Quick memory aide :
x is across ( a cross!!)

The time the reaction takes is dependent upon the amount of acid, so time would be the dependant variable.
(The volume isn't a great choice of measurement BTW, teacher!!)

Probably the exp is something like to add acid to e.g. a bit of magnesium and time how long it takes for the Mg to dissolve.

Yes, plotting time against vol will give a straight line from the left going down. To get a line going through the origin (0,0), change time to the inverse ( 1 divided by time) but that will give some slightly tricky numbers for a Y7!!

Original Poster

Wow guys thanks tons. If my son is to be believed (?) they were just given the info and told to do the graph they weren't told what the experiment was actually about so I agree it is a bit confusing. It wasn't an experiment done in the class.
Think we may do both as he is worried about getting it wrong and then he can hand in the correct one.
Thank you to everyone, I am amazed how thorough and helpful you have all been. Wish i could still rep you.

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