Science Buddies: "Ask an Expert"

I am doing a project with the question being what does freezing and boiling water do to rocks?
After doing the project 3 times I came up with the results being nothing happens to the rocks.
I checked the rocks in 30 minutes, 1 hour and 9 hours.
How would I make a graph to reflect this data?

A graph is not suited to represent your results. Your statement in your post is a good representation of your results. You might be more specific about "nothing happens". Some things that might have changed would be the weight of the rock, the color of the rock, or the appearance of the surface as seen with a magnifier or microscope. One thing that I have read that can happen to rocks when freezing them is that water can get into a crack and, when the water freezes, the expansion of the water can crack the rock. Thus it might be interesting to include a rock with a crack or crevice in it. It might be a good idea to wrap this rock in a small towel before freezing it just in case it cracks with enough force to send the shards flying if it were not confined.

To add to John's reply, you can also rank your observations: macro or micro-damage. Basically, you would create an index (converting your observations to numbers). Then plot your observations in a scattered graph in which Y axis represents the index and X axis represents the temperature. Example, when you put a piece of rock in -11 degrees, you see the changes which match to the index number 3 based on the description that you already came with. So your dot on the graph will be the cross point of two perpendicular lines passing through -11 on X axis and 3 on Y axis. If you connects all these dots from various observations, you would see a trend line showing the effect of temperature on the extend of damages on a rock.

There are limitations in summarizing your observation to numbers; this method is often referred to a semi-quantitative measurement of a phenomenon.

An example ranking would be: Let's say from the most destructive changes to the least destructive changes.
You can define the description as you like. Of course, it is very important to clearly explain these descriptions in your project.

Index Description
5 cracks detected by a naked eye + change in the color + etc
4 cracks detected by a magnifier + change in color
3 change in color ...
.
.
.
0 No changes

I hope that this helps.

Good luck,
-Rooz