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Choosing Contexts and Experiments that Help Students Make Connections in Chemistry RET Program Summary. Brian Corry Summer 2012/13. Designing Curriculum Units that Help Students Make Connections in Chemistry RET Program Summary. Brian Corry Summer 2012/13. My background. - PowerPoint PPT Presentation
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Choosing Contexts and Experiments that Help Students Make Connections in Chemistry
RET Program Summary
Brian CorrySummer 2012/13
Designing Curriculum Units that Help Students Make Connections in Chemistry
RET Program Summary
Brian CorrySummer 2012/13
My background• Arrowhead High School
– Hartland, WI– AP Chemistry– General Physics and AP Physics
• Procter & Gamble– Cincinnati, OH– Researcher, Drying and Particle
Formation
• University of Illinois– Champaign, IL– BS Chemistry
Presentation Outline• Summary of RET Experiences and
Research• Connecting the research to chemistry
education / instructional model• Design criteria for curriculum that
helps students make connections• Curriculum Unit Example
RET Program• Research Experience for
Teachers– University of Wisconsin –
Milwaukee– Supported by NSF– Objective: collaborate with
MS / HS science teachers to improve the quality of science education
My Faculty Mentor• Dr. Alan Schwabacher
– UWM– PhD, Columbia– Organic Chemistry– Research focuses on
mimicking the selective binding of biological molecules
Catalyzed Hydrolysis of
BNPPChem 582 at UWM
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
bis(p-nitrophenyl) phosphate (BNPP) p-nitrophenol
Slow
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
p-nitrophenol
Cu2+, Fast
bis(p-nitrophenyl) phosphate (BNPP)
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
p-nitrophenol
Cu2+, Fast
bis(p-nitrophenyl) phosphate (BNPP)
Michaelis-Menten Kinetics
Hydrolysis of BNPP
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
Hydrolysis of a phosphate diester
Phosphate diesters are extremely important biologically
Hydrolysis of BNPP
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
Biochemistry
Hydrolysis of a phosphate diester
Kinetics / Catalysis
RateCatalyst?
O-
NO2
pKa = 7.16
Acid / Base
Yellow
pKa = 2.79pKa1 = 0.30 pKa2 = 4.96
O2N
O
P
OH
O-
O
O-
NO2
+
O2N
O
P
O
O-
O
NO2
+ OH2
Hydrolysis of BNPP
O2N
O
P
O
OHO
NO2
+ OH2
OH
NO2O2N
O
P
OH
OHO
+
Biochemistry
Hydrolysis of a phosphate diester
Kinetics / Catalysis
RateCatalyst?
O-
NO2
pKa = 7.16
Acid / Base
Yellow
Analytical / Spectroscopy
pKa = 2.79pKa1 = 0.30 pKa2 = 4.96
Hydrolysis of BNPP
Biochemistry
Kinetics / Catalysis Acid / Base
Analytical / Spectroscopy
10 g BNPP = $31510 g NaBNPP = $1500
Synthesis of BNPP
Synthesis of TNPP
250 g = $36 50 g = $27
O2N O
P
O
O
O
O2N
NO2
Et3N, CH 2Cl2+ 3 Et3NH+Cl-
1st time: 53% yield2nd time: 70% yield
PCl
O
Cl
Cl + 3
OH
NO2
TNPP
O2N O
P
O
O
O
O2N
NO2
+ OH2M EK, reflux
O2N
O
P
O
OHO
NO2
+
OH
NO2BNPP
1st time: 46% yield2nd time: 52% yield $400
Hydrolysis of BNPP
Biochemistry
Kinetics / Catalysis Acid / Base
Analytical / Spectroscopy
Hydrolysis of BNPP
Biochemistry
Kinetics / Catalysis Acid / Base
Analytical / Spectroscopy
Synthesis of TNPP/BNPP
Organic Synthesis
NMR / Characterization
Extraction / Purification TLC / Polarity
Absorbance is directly proportional to [PNP] =
Beer’s Law
O-
NO2
We can monitor the progress of reactions.
OH-
O2N
O
P
O
O-
O
NO2
O2N
O
P
OH
O-
O
+
O-
NO2
Rate is not first order…
…if you ignore ionic strength.
OH-
O2N
O
P
O
O-
O
NO2
O2N
O
P
OH
O-
O
+
O-
NO2
Rate is first order with respect to hydroxide.
OH-
O2N
O
P
O
O-
O
NO2
O2N
O
P
OH
O-
O
+
O-
NO2
Rate is first order with respect to BNPP.
OH-
O2N
O
P
O
O-
O
NO2
O2N
O
P
OH
O-
O
+
O-
NO2
A catalyst increases the rate of reaction.
Outcomes• Chemistry 582
– More effective synthetic route for BNPP– Students make their own reagents– Michaelis-Menten kinetics (not yet?)
• AP Chemistry– Access to expensive materials– Phosphate esters– PNP in Beer’s Law activity– BNPP to study kinetics/catalysis
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Collaboration Infrequent. Perhaps different groups pooling data.
Constant. Shared ownership of separate pieces.
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Collaboration Infrequent. Perhaps different groups pooling data.
Constant. Shared ownership of separate pieces.
Peer learning / communication
Rare. Some models of project-based learning.
Researchers and students teach one another.
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Collaboration Infrequent. Perhaps different groups pooling data.
Constant. Shared ownership of separate pieces.
Peer learning / communication
Rare. Some models of project-based learning.
Researchers and students teach one another.
Role of content Content is the focus. Laboratory experiences are a vehicle for investigating the content.
Chemistry content is obtained and used in the service of answering a research question.
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Collaboration Infrequent. Perhaps different groups pooling data.
Constant. Shared ownership of separate pieces.
Peer learning / communication
Rare. Some models of project-based learning.
Researchers and students teach one another.
Role of content Content is the focus. Laboratory experiences are a vehicle for investigating the content.
Chemistry content is obtained and used in the service of answering a research question.
Assessment of outcomes
Separates content and lab practices objectives. Original research findings seldom critiqued.
Integrates laboratory and content. Research findings necessarily critiqued.
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Primary owner Instructor Researcher or student
Collaboration Infrequent. Perhaps different groups pooling data.
Constant. Shared ownership of separate pieces.
Peer learning / communication
Rare. Some models of project-based learning.
Researchers and students teach one another.
Role of content Content is the focus. Laboratory experiences are a vehicle for investigating the content.
Chemistry content is obtained and used in the service of answering a research question.
Assessment of outcomes
Separates content and lab practices objectives. Original research findings seldom critiqued.
Integrates laboratory and content. Research findings necessarily critiqued.
Topics / disciplines One at a time. Some topics will be merged in advanced classes.
Multidisciplinary. Boundaries between topics blurred.
“When a school subject is taught for which there is a
professional counterpart, there should be a conceptual
connection to post-secondary studies and to the practice of that subject in the real world.”
National Research Council. (2009). Engineering in K-12 education: Understanding the status and improving the prospects. Washington, DC: The National Academies Press.
Standard Chemistry Education
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Structure
Content / Context
ChemistryExpected Outcome
Standard Chemistry Education
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Structure
Actual Outcome Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
“Your system is perfectly designed
to give you the results you're
getting.”W. Edwards Deming
Which outcome do we want?
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Content / Context
Chemistry
Outcome 1
Outcome 2
Unit Expectations
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Structure
Content / Context
ChemistryExpected Outcome
Course Expectations
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Structure
Content / Context
ChemistryExpected Outcome
Alternative Model
Content
Unit 1
Context
Content
Unit 2
Content
Unit 3
Content
Unit 4
Structure
Content / Context
ChemistryExpected Outcome
Alternative Model
Content
Unit 1
Context
Content
Unit 2
Content
Unit 3
Content
Unit 4
Structure
Content / Context
ChemistryExpected Outcome
Alternative Model
Content
Unit 1
Context
Content
Unit 2
Content
Unit 3
Content
Unit 4
Structure
Content / Context
ChemistryExpected Outcome
Important Design Consideration
Content
Unit 1
Content
Unit 2
Content
Unit 3
Content
Unit 4
Structure
ChemistryExpected Outcome
Context
Content / Context
Important Instructional Consideration
Context
Content
Unit 2
Content
Unit 3
Content
Unit 4
Structure
Content / Context
ChemistryExpected Outcome
Content
Unit 1
http://chemistry.beloit.edu/modules.html
These 2-4-week modules start with relevant real-world questions and develop the chemistry needed to answer them. In the process, students model how chemistry is actually done and discover connections between chemistry and other sciences, technology, and society.
Other curriculum materials
ACS CLUE Living by Chemistry
3 Important Design Criteria
Context
Connections
Questions
AP Chemistry “Big Ideas”
Big Ideas
Atomic Structure
Structure and
Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
AP Chemistry “Big Ideas”
Big Ideas
Atomic Structure
Structure and
Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
UnitsAtomic
Structure
Structure and Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
1
2
3
4
5
6
Context
Atomic Structure
Structure and Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
ACS Anchoring Concept Content Map (ACCM)
Context
Atoms
Bonding
Structure & Function
Inter-molecular
forces
ReactionsEnergy / Thermo-dynamics
Kinetics
Equilibrium
Experiments, Measurement
& Data
Visualizations
Context Example: NH3
• Bonding and structure• IMFs and Properties• Reactions and Stoichiometry
– Haber Process– Acid-base / Complex Ions
• Kinetics• Equilibrium• One problem: Data and experimentation
(Haber)
NH3 Production
Atomic Structure
Structure and Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
Context
Atomic Structure
Structure and Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
3 Important Design Criteria
•Rich enough to touch all “big ideas”•Explicitly developed to address them all•Appropriate level / familiarity
Context•Modeling the use of the big ideas to make
connections•Students are challenged to make these
connections
Connections
•Effective vehicle for making connections•Requires/promotes student engagement•Teachers need well-planned progressions
Questions
Classroom vs. Research LabFeature High School Chemistry Graduate Chemistry Research
Focus of work Units of content Research question
Science, 1987, 235, 1173-1178
Organic Phosphates
Atomic Structure
Structure and Properties
Reactions
Kinetics
Thermo-dynamics
Equilibrium
Traditional: How is DNA built?
DNA
Bases Ribose Phosphate
Introductory Activity
DNA is made up of…
Traditional: How is DNA built?
DNA
Bases
Structure
Function
Ribose
Structure
Function
Phosphate
Structure
Function
Introductory Activity
Alternative: What does DNA have to do?(and what about its structure allows it to do this?)
DNA
Functions
Information
Bases
Structure
Framework
Ribose
Structure
Glue
Phosphate
Structure
Introductory Activity
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
Why not A/G and T/C?
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
N
N
N
N
NH H
Ribose
A den ine
N
N
N O
H
H
Ribose
C ytos ine
N
N
N
N
N
O
Ribose
H
H
H
G uan ine
N
N
O
O
CH3
Ribose
H
Thym ine
PurinesPyrimidines
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
How do they hold together?
Why not A/G and T/C? Structural models / “rung” building Uneven spacing of ladder rails
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
Structural models
C ytos ineG uan ine
N
N
ON
NRibose
N
H
H
H
N
N
RiboseO
N
H
H
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
How do they hold together? Structural models Hydrogen bonds
Why not A/G and T/C? Structural models / “rung” building Uneven spacing of ladder rails
Why not A/C and T/G?
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
DNA Base Pairing Applet
http://chemmac1.usc.edu/java/bases/basepairs.html
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
What do base pairs do (dynamically) in DNA? Replication process
How do they hold together? Structural models Hydrogen bonds
Why not A/G and T/C? Structural models / “rung” building Uneven spacing of ladder rails
Why not A/C and T/G? Structural models / pairing applet No H-bond match up
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
What do base pairs do (dynamically) in DNA? Replication process Hold together and break apart
How do they hold together? Structural models Hydrogen bonds
How do they break apart?
Replication animations
Why not A/G and T/C? Structural models / “rung” building Uneven spacing of ladder rails
Why not A/C and T/G? Structural models / pairing applet No H-bond match up
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/
Driving QuestionWhy did nature choose those bases and pair them that way?
What do base pairs do (statically) in DNA?
Questions Investigations
Structure of DNA polymers
Explanations
“Rungs” of the ladder
What do base pairs do (dynamically) in DNA? Replication process Hold together and break apart
How do they hold together? Structural models Hydrogen bonds
How do they break apart?
Replication animations DNA helicases
Why not A/G and T/C? Structural models / “rung” building Uneven spacing of ladder rails
Why not A/C and T/G? Structural models / pairing applet No H-bond match up
What must each “rung” do? Ladder
1) Code information2) Space the rails evenly3) Hold the rails together
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate?
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate? Drawing LDS Common oxyanion with resonance forms, conjugate base of H3PO4
What is phosphoric acid? Working with LDS
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate? Drawing LDS Common oxyanion with resonance forms
What is phosphoric acid? Working with LDS Phosphate group with a hydrogen
attached to three oxygens
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
How acidic is phosphoric acid? Titration curve
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate? Drawing LDS Common oxyanion with resonance forms
What is phosphoric acid? Working with LDS Phosphate group with a hydrogen
attached to three oxygens
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
How acidic is phosphoric acid? Titration curve pKa values for three acidic
hydrogens
How does pH affect ionization?
Henerson-HasselbalchChemistry Version (what’s the pH?)
acidbaselogppH aK
Biochemistry Version (what’s there at that pH?)
aKppH10acidbase
H2PO4- HPO4
2-H3PO4
PO43-
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate? Drawing LDS Common oxyanion with resonance forms
What is phosphoric acid? Working with LDS Phosphate group with a hydrogen
attached to three oxygens
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
How acidic is phosphoric acid? Titration curve pKa values for three acidic
hydrogens
How does pH affect ionization?
HH Calculations / Speciation Curve
pH determines extent of ionizationAt pH=7, 50/50 H2PO4
-/HPO42-
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester?
OHP
O
OHOH
OP
O
OHOH
R
Phosphoric Acid Phosphate Ester
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
How many hydrogens are replaced?
OHP
O
OHOH
OP
O
OHOH
CH3
OP
O
OHO
CH3
CH3
OP
O
OO
CH3
CH3
CH3
Phosphoric Acid Phosphate monoester
Phosphate triesterPhosphate diester(like DNA)
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
What does replacing hydrogen do to acidity?
Mono/di/tri ester consideration
How many hydrogens are replaced? Research It depends. There are phosphate
mono-, di-, and tri- esters.
OHP
O
OHOH
OP
O
OHOH
CH3
OP
O
OHO
CH3
CH3
OP
O
OO
CH3
CH3
CH3
Phosphoric Acid Phosphate monoester
Phosphate diester(like DNA)
Phosphate triester
1
23 1
1
2
No acidic hydrogens
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
What does replacing hydrogen do to acidity?
Mono/di/tri ester consideration
Triesters have 0 acidic hydrogens. Diesters have 1, monoesters 2.
What are the relative pKas for each of these?
How many hydrogens are replaced? Research It depends. There are phosphate
mono-, di-, and tri- esters.
Handbook of Biochemistry and Molecular Biology
OHP
O
OHOH
OP
O
OHOH
CH3
OP
O
OHO
CH3
CH3
OP
O
OO
CH3
CH3
CH3
Phosphoric Acid Phosphate monoester
Phosphate triester
1
23 1
1
2pKa1 = 2.1
pKa2 = 7.2 pKa3 = 12.3 pKa1 = 1.5
pKa2 = 6.3
pKa = 1.3 No acidic hydrogens
Phosphate diester(like DNA)
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
What does replacing hydrogen do to acidity?
Mono/di/tri ester consideration
Triesters have 0 acidic hydrogens. Diesters have 1, monoesters 2.
What are the relative pKas for each of these? Research pKa1 ≈ 1-2 for all
How many hydrogens are replaced? Research It depends. There are phosphate
mono-, di-, and tri- esters.
What are the major species at pH = 7?
OHP
O
OHOH
OP
O
OHOH
CH3
OP
O
OHO
CH3
CH3
OP
O
OO
CH3
CH3
CH3
Phosphoric Acid Phosphate monoester
Phosphate triester
1
23 1
1
2pKa1 = 2.1
pKa2 = 7.2 pKa3 = 12.3 pKa1 = 1.5
pKa2 = 6.3
pKa = 1.3 No acidic hydrogens
Phosphate diester(like DNA)
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
What does replacing hydrogen do to acidity?
Mono/di/tri ester consideration
Triesters have 0 acidic hydrogens. Diesters have 1, monoesters 2.
What are the relative pKas for each of these? Research pKa1 ≈ 1-2 for all
How many hydrogens are replaced? Research It depends. There are phosphate
mono-, di-, and tri- esters.
What are the major species at pH = 7?
pKa, Calculations, graphs
Phosphate diesters are ionized at pH 7.
Where is the “A” in DNA?
Driving QuestionWhy did nature choose phosphates?
How is DNA like phosphoric acid?
Questions Investigations
Structure of DNA polymers
Explanations
Two hydrogens replaced by a carbon of the ribose
What is a phosphate ester? Research Phosphoric acid with carbon groups
replacing the hydrogens
What does replacing hydrogen do to acidity?
Mono/di/tri ester consideration
Triesters have 0 acidic hydrogens. Diesters have 1, monoesters 2.
What are the relative pKas for each of these? Research pKa1 ≈ 1-2 for all
How many hydrogens are replaced? Research It depends. There are phosphate
mono-, di-, and tri- esters.
What are the major species at pH = 7?
pKa, Calculations, graphs
Phosphate diesters are ionized at pH 7.
Where is the “A” in DNA? Discussion DNA is not an “acid” at pH 7
Driving QuestionWhy did nature choose phosphates?
What does that piece of the chain have to
do?
Questions Investigations
Structure of DNA polymers
Explanations
Link things in the DNA chain.
What type of bonding behavior is required? Discussion The unit in that space has to be
able to link at least two times
What elements / groups could do this? Brainstorming Yes: O, S, N, P, As, molecule
No: H, Halogens
What is a phosphate? Drawing LDS Common oxyanion with resonance forms
What is phosphoric acid? Working with LDS Phosphate group with a hydrogen
attached to three oxygens
Nature uses phosphates. Let’s learn about those and assess some of the alternatives later.
How acidic is phosphoric acid? Titration curve pKa values for three acidic
hydrogens
How does pH affect ionization?
HH Calculations / Speciation Curve
pH determines extent of ionizationAt pH=7, 50/50 H2PO4
-/HPO42-
O
P OO-
O
R2
R1
O
R1
R2 O
CO
O
R2
R1
O
S OO
O
R2
R1
O
As OO-
O
R2
R1
OO
O OO
-O
OH
R2R1
Phosphate esterEther
Ester Sulfate Ester
Citrate(?) EsterArsenate Ester
Driving QuestionWhy did nature choose phosphates?
What’s the importance of being ionized?
Questions
Solubility
Kinetics
Energetics
3 Important Design Criteria
•Rich enough to touch all “big ideas”•Explicitly developed to address them all•Appropriate level / familiarity
Context•Modeling the use of the big ideas to make
connections•Students are challenged to make these
connections
Connections
•Effective vehicle for making connections•Requires/promotes student engagement•Teachers need well-planned progressions
Questions
The role of experiments
Content
Unit 1
Context
Content
Unit 2
Context
Content
Unit 3
Context
Content
Unit 4
Context
Design 1
Design 2Questions Investigations Explanations
How acidic is phosphoric acid? Titration curve pKa values for three acidic
hydrogens
