Gro-Beast
Objectives: If you complete all of these activities, you will be able to describe metric readings
from graduated cylinders; compare and order a set of objects according to a measurement; make
predictions before measuring; measure the length, mass and volume of objects using the
appropriate metric instruments; and record and graph data.
Materials Needed: Gro-Beasts, container, water, balance, ruler, graduated cylinder.
Activity: You probably will not do all of the activities listed here. The activities you choose
will depend on your grade level and the measuring devices available to you.
Measure the length of your Gro-Beast, either from head to tail or wingtip to wingtip,
whichever is greater. If you have a balance, measure the mass of your Gro-Beast. Later on, we
will construct a homemade balance. Record the time when you make these measurements.
The Beasts will grow too large to put in ordinary-sized graduated cylinders, but you can
still measure their volume. Put some water in a clear plastic cup. Mark the water level. Add the
Gro-Beast. Mark the new water level. Without removing your Gro-Beast, pour water from the
cup into the graduated cylinder until the water is back to its original level. If you were careful,
the volume of water in the graduated cylinder is equal to your Gro-Beast’s volume.
Leave your Gro-Beast in the container of water. Predict what you think will happen.
Periodically measure your Gro-Beast. Do this frequently at first, until you get an idea of what is
happening. Make a graph or bar chart of mass, length, or volume versus time. Fill in the table
below. Be sure to specify whether “result” is mass, length, or volume, and be sure to give units.
Other ideas for activities: give each Gro-Beast a name. Invent a story about your
Gro-Beast. Tell about its life, what its world is like, and what it did today. Older children can
look up their particular Gro-Beast in the encyclopedia and write a report on it. Color or construct
a dinosaur-times diorama for the Gro-Beasts to "live" in.
Gro-Beast Data Table
Date Time Result Date Time Result Date Time Result
Further Investigation: The Gro-Beast’s density is its mass divided by its volume. How do
you think its density will change over time. How does its density change? Explain.
Scientific Graphing
Objectives: After you have completed this activity, you should be able to make and interpret
graphs.
Materials Needed: Graph paper and pencil or computer and graphing program, data.
Activity: Graphs are used to convey information. Scientists expect graphs to follow standard
formats. Different scientists may use different formats, but the ones given here are understood
by all. However, if your curriculum requires that you use a different format for graphs, do not
hesitate to follow your curriculum. This activity uses your gro-beast mass data in constructing a
graph, but the instructions are the same for any kind of data.
1. Before you do a graph, you need to have some data.
If your experiment is simple, which is preferable, you
will have a single variable which you control, called the
independent variable, and a single variable which you
measure, called the dependent variable. For example,
you controlled the time when you measured the mass of
your gro-beasts, so time is the independent variable.
You actually measured the mass of your gro-beasts, so
mass is the dependent variable.
2. The independent variable is usually marked off along the horizontal, or x-axis. The
dependent variable (the thing you measure) is usually marked off along the vertical, or y-axis. If
you like to confuse people, switch these around.
3. You need to carefully choose the units for your axes.
We typically measure our gro-beast mass over a period of
of 9 or 10 days. You could mark off the horizontal axis in
units of days. However, because your measurements may
be spaced only a few hours apart, it may be better to mark
off the x-axis in units of hours. 9 days is 226 hours, so it
would be convenient for your x-axis to extend from 0
hours (when you first got your beast) to 250 hours. If
your beast started at 5 grams and reached a maximum of
39 grams, you might want to mark off your y-axis so it
extends from 0 to 40 (or maybe 50) grams. What if you
start a graph and a few days later find you set your axes up wrong? Well, paper is cheap, and the
electrons your computer uses are cheaper. When in doubt, start over and do it right.
4. Now you are ready to plot some data. Suppose
your gro-beast had a mass of 5 grams when you
first put it in water, and suppose you want to call
the time zero when you first put it in water. You
need to go horizontally to zero and up 5, then plot
the data point using a convenient symbol (I'll use
a closed circle here). Because scientists often put
their plots in boxes (for neatness) and because the
graphing program I use does it automatically, I'll
surround the whole plot by a box. Here's the
graph with the first point plotted. Notice my
graphing program only plotted half of the circle,
because the horizontal axis didn't extend to negative
numbers. On paper, do a whole circle centered horizontally at 0.
5. Suppose my first measurement (5 grams) was
at 10 a.m., and suppose at noon, the beast had a
mass of 7.5 grams. To plot this second data
point, go horizontally to 2 (noon minus 10 a.m. is
2 hours) and up to 7.5, and draw a circle. You can
still barely see this point, because 2 hours out of
250 is not very much. The only tricky part here is
calculating the elapsed time from when you put
your beast in water to when you took the
measurement.
6. I've invented some more data which give a
"typical" gro-beast growth curve. They grow
most rapidly when you first put them in water, and
shrink most rapidly when you first take them out
of water. The curves are usually fairly smooth.
Notice how I have connected the data points by
lines, which help your eye see the growth and
shrinking trends. These lines don't really mean
anything, and some scientists will complain if you
draw in "connect-the-dot" lines. Don't worry,
scientists like to complain. If the lines were some
theoretical calculation which was supposed to match the
data, then the lines really would be meaningful and scientists wouldn't
complain. I like to put the "connect-the-dot" lines in except in special circumstances.
7. If you want to use bar charts to represent your beast's growth, go right ahead. Graphs are
meant to convey information. If your bar chart conveys useful information, it is reasonable to
make one.