Mr. Guch's rules for Good Graph
Making:
1. Always give your graph a title
in the following form: "The dependence of (your dependent variable) on
(your independent variable).
Let's say that you're doing a graph
where you're studying the effect of temperature on the speed of a reaction.
In this reaction, you're changing the temperature to known values, so the
temperature is your independent variable. Because you don't know the speed
of the reaction and speed depends on the temperature, the speed of the
reaction is your dependent variable. As a result, the title of your graph
will be "The dependence of reaction rate on temperature", or something
like that.
2. The x-axis of a graph is always
your independent variable and the y-axis is the dependent variable.
For the graph described above, temperature
would be on the x-axis (the one on the bottom of the graph), and the reaction
rate would be on the y-axis (the one on the side of the graph)
3. Always label the x and y axes
and give units.
Putting numbers on the x and y-axes
is something that everybody always remembers to do (after all, how could
you graph without showing the numbers?). However, people frequently forget
to put a label on the axis that describes what those numbers are, and even
more frequently forget to say what those units are. For example, if you're
going to do a chart which uses temperature as the independent variable,
you should write the word "temperature (degrees Celsius)" on that axis
so people know what those numbers stand for. Otherwise, people won't know
that you're talking about temperature, and even if they do, they might
think you're talking about degrees Fahrenheit.
4. Always make a line graph
Never, ever make a bar graph when doing
science stuff. Bar graphs are good for subjects where you're trying to
break down a topic (such as gross national product) into it's parts. When
you're doing graphs in science, line graphs are way more handy, because
they tell you how one thing changes under the influence of some other variable.
5. Never, EVER, connect the dots
on your graph!
Hey, if you're working with your little
sister on one of those placemats at Denny's, you can connect the dots.
When you're working in science, you never, ever connect the dots on a graph.
Why? When you do an experiment, you
always screw something up. Yeah, you. It's probably not a big mistake,
and is frequently not something you have a lot of control over. However,
when you do an experiment, many little things go wrong, and these little
things add up. As a result, experimental data never makes a nice straight
line. Instead, it makes a bunch of dots which kind of wiggle around a graph.
This is normal, and will not affect your grade unless your teacher is a
Nobel prize winner. However, you can't just pretend that your data is perfect,
because it's not. Whenever you have the dots moving around a lot, we say
that the data is noisy, because the thing you're looking for has a little
bit of interference caused by normal experimental error.
To show that you're a clever young
scientist, your best bet is to show that you KNOW your data is sometimes
lousy. You do this by making a line (or curve) which seems to follow the
data as well as possible, without actually connecting the dots. Doing this
shows the trend that the data suggests, without depending too much on the
noise. As long as your line (or curve) does a pretty good job of following
the data, you should be A-OK.
6. Make sure your data is graphed
as large as possible in the space you've been given.
Let's face it, you don't like looking
at little tiny graphs. Your teacher doesn't either. If you make large graphs,
you'll find it's easier to see what you're doing, and your teacher will
be lots happier.
So, those are the steps you need
to follow if you're going to make a good graph in your chemistry class.
I've included a couple of examples of good and bad graphs below so you
know what these things are supposed to look like. |
