Transcript Improving Experimental Design

Gateway High School Science Department
Chemistry/Physics
[email protected]
Reading, Writing, Speaking
and Listening
Science and Technology
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CFF Laptops
CFF Digital Projector
Vernier Lab Pros
Vernier Temperature Probes
LoggerPro (Vernier Software for data
collection)
Microsoft Word
Microsoft PowerPoint
Moodle
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Before Experiment:
◦ Students in an academic chemistry class
are challenged to be able to design and
carry out an experiment to determine the
effects of adding salt to ice on the
freezing point water and whether or not
the changing of the freezing point is a
colligative property
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During Experiment:
◦ Lab groups must jigsaw in order to divide
up all of the salt and ice ratios in a timely
manner
◦ Students measure temperatures using
Venier LabPros, Vernier temperature
probes and CFF laptops
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After Experiment:
◦ Individual lab groups format LoggerPro
graphs into Microsoft Word documents
and post results to online forum (at
Gateway School District this is Moodle)
◦ Each group presents a brief PowerPoint
that outlines their results and preliminary
conclusions
◦ Each lab group retrieves all other groups
results in order to write complete the
required lab report
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Chemical Kinetics
◦ How molecules translate
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Colligative Property
◦ Property that depends on the concentration of solute
molecules or ions in a solution but not on the chemical
identity of the solute
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Systematic Error
◦ Error that arises from a flaw in equipment or the design
of an experiment
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Random Error
◦ Error that arises from the effects of uncontrolled (and
may be uncontrollable) variables in the measurement
(Ebbing and Gammon 2005)
(Harris 2003)
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Salts (same # molecules for each):
◦ Sodium chloride (NaCl)
 5.8 g
◦ Calcium chloride (CaCl2)
 11.1 g
◦ Ammonium chloride (NH4Cl)
 5.4 g
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Coffee cups and scoopula
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Water (ice)
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Mixing vs. Not Mixing
◦ 100 g
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Mixing vs. Not Mixing plays a big role in
gathering accurate data
Insulating the system also plays a role
◦ One vs. multiple coffee cups
◦ Lids?
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Time is a factor
◦ An initial trial run is needed to establish an
adequate time frame
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Many students predict that the freezing point of
water should increase when the salt is added
◦ Does this make sense?
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Many students in each class perceived (after the
experiment) that simply conducting more trials
would improve results
◦ Only addresses random error
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Some students immediately recognize that each
groups’ procedures must be adjusted to the
same length and involve stirring to eliminate
systematic error
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The National and PA Science Standards state
the need for understanding the nature of
science
Science education needs to stress both
content AND the process of science in order
to promote scientific literacy
◦ Students come from various elementary and middle
school settings (and sometimes other districts)
◦ Students usually take chemistry after Earth and
space science and biology
◦ The nature of science needs to be stressed in all
levels of science education
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The technology is easy to use and not very
time consuming
Don’t feel overwhelmed!
The Vernier technology can be used in
numerous other variations and applications
◦ Chemistry, Physics, Biology, and others
Vernier equipment is designed to mix and
match
Vernier equipment is reasonably priced and
basic startup equipment could be obtained
by mini grants
Forum software can be obtained for the
entire school
[email protected]