Exp. 1:
Exploding Particles
Required Locker Materials:
-
Ceramic evaporating dish
50ml beaker
Forceps / tweezers
Crucible tongs
Safety:
-
Safety eyewear: MUST BE WORN WITH
BUNSEN BURNER
Waste:
-
All popcorn waste can be disposed in
the normal trash bin
Experimental Objective:
Students will learn to use a Bunsen burner correctly. In addition students will learn to use
statistical methods to determine the precision of their experimental trials.
This experiment exposes students to the difficulties of repeating an experiment multiple
times and obtaining reproducible and consistent data. The use of statistical methods will
allow assessing the quality of the measured data.
Procedure
For this experiment record all observations and measurements in your notebook:
1. Sprinkle 20 to 25 kernels of popcorn into a dry, 50ml beaker. (Handling of the kernels
probably should be done with tweezers unless your fingers are exceptionally dry.)
2. Obtain a porcelain spot plate
3. Weigh one kernel on the mass balance and place it into a plate compartment.
4. Repeat this process until you have gathered ten kernels of similar size and mass.
5. Light the Bunsen burner.
6. With the unweighed pieces, develop a technique of popping each kernel singly without
scorching or fragmenting it. Use a beaker or an evaporating dish as the popper and a
cool burner flame as the heat source. Agitate the container, if necessary, with some sort
of holder or (if you are less sensitive) with your fingers. You may find that a direct
approach is successful, like waving the beaker and kernel over the flame, or that a more
subtle method is desirable-preheating the container. The object here is to obtain, with
consistency, completely-flowered, unscorched and unfragmented kernels.
7. Repeat this process with unweighed kernels until you are confident in the consistency of
your technique.
8. Pop and record the mass for each of the kernels placed in your spot plate.
9. Clean up and dispose of all kernels in a trash bin.
Calculations
For the calculation start a new section in your notebook. Remember you need to show
every calculation you do by writing down the equation and an example calculation. The
example calculation only needs to be done for one trial. The results of the remaining trials
can be written down in a table in your notebook.
Mass difference of popped vs. unpopped kernels
The mass difference is determined by calculating the difference in mass between popped
and unpopped kernels.
In general, physical changes of solids do not coincide with any change in mass.
Exp. 1
Leo Truttmann – Fall 13
%mass loss of kernels
In order to compare the different trails with each other we need to determine the % mass
loss of each kernel. Because each kernel has a different mass, the absolute mass loss will
be different for each trial. The relative loss (or %mass loss) should be more similar in each
trial, and therefore more useful to use in the following statistical analysis.
The %mass loss can be calculated according to following equation:
⌈mdiff ⌉
%mass loss =
mi,unpopped
× 100%
Average %mass loss
Average the %mass loss of all ten trials.
Standard Deviation of mass %mass loss
Following equation can be used to calculate the Standard Deviation:
St. Dev. =
∑(xi −x̅)2
n−1
%Precision
The %Precision is a measure of how reproducible your data set is. The smaller the number
the more precise in general a set of measurements are.
Std.Dev.
%Precision = average × 100%
Questions and Discussions
After you finished all the calculations write a short answer for each of the following
questions and discuss your answer.
1. What causes the weight difference? How could it be proven?
2. Does the popping result in a physical or chemical change.
3. Could any type of ”dried’’ kernel be used?
Exp. 1
Leo Truttmann – Fall 13