Lesson plan
pH, Pigments and Photos
Students will investigate what causes colors in nature & the movement of pigments through chromatography paper, determine pH values & the components of an unknown dye mixture, use technology to quantify a visual color value, analyze the results of the molecule separation by gel electrophoresis, and predict how additional molecules would have migrated in gel electrophoresis based upon size and charge.
Grades 6–8Chemistry & Matter
Overview
Students investigate what causes color in nature and how scientists separate and measure the molecules behind it. After videos on how bees find flowers and why blue is rare in nature, they extract pigments from leaves with isopropanol and separate them by paper chromatography. They use the CarolinaRGB phone app to read RGB values of pH strips and design a procedure to find the pH of unknown water samples. Students write a constructed response that graphs chromatography data, fits a line of best fit, and predicts pigment travel. In a gel electrophoresis lab they identify dyes in three unknown mixtures using six standards, then make posters for a gallery walk. The plan gives one 45-50-minute class period each for the engagement and elaboration labs, and one to two periods for exploration.
Lesson Objectives
- Investigate what causes colors in nature & the movement of pigments through chromatography paper, determine pH values & the components of an unknown dye mixture, use technology to quantify a visual color value, analyze the results of the molecule separation by gel electrophoresis, and predict how additional molecules would have migrated in gel electrophoresis based upon size and charge. SCIENTIFIC INQUIRY SKILLS.
- Pose questions and form hypotheses.
- Design and conduct scientific investigations.
- Use experimental data to make conclusions about the initial question and to support or refute the stated hypothesis.
- Follow laboratory safety rules and regulations. LABORATORY TECHNICAL SKILLS.
- Demonstrate proper use of micropipettes.
- Consider safety considerations when working with an electric current.
- Make dilute solutions from concentrated stock solutions.
- Demonstrate proper use of gel electrophoresis equipment.
- Prepare and pour agarose gels.
Standards
NGSS · 5
- MS-PS2-5Use scientific evidence to argue that fields exist between objects with mass, between magnetic objects, and between electrically charged objects that exert force on each other even though the objects are not in contact.
- HS-PS1-3Cite evidence to relate physical properties of substances at the bulk scale to spatial arrangements, movement, and strength of electrostatic forces among ions, small molecules, or regions of large molecules in the substances. Make arguments to account for how compositional and structural differences in molecules result in different types of intermolecular or intramolecular interactions.
- HS-PS2-6Communicate scientific and technical information about the molecular-level structures of polymers, ionic compounds, acids and bases, and metals to justify why these are useful in the functioning of designed materials.
- HS-PS3-5Develop and use a model of magnetic or electric fields to illustrate the forces and changes in energy between two magnetically or electrically charged objects changing relative position in a magnetic or electric field, respectively.
- HS-ETS1-1Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants.
CCSS Math · 9
- MP2Reason abstractly and quantitatively.
- MP4Model with mathematics.
- HSF-BF.A.1Write a function that describes a relationship between two quantities.
- HSF-IF.C.7Graph functions expressed symbolically and show key features of the graph, by hand in simple cases and using technology for more complicated cases.
- HSN-Q.A.1Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays.
- HSN-Q.A.2Define appropriate quantities for the purpose of descriptive modeling.
- HSN-Q.A.3Choose a level of accuracy appropriate to limitations on measurement when reporting quantities.
- HSS-IC.A.1Understand statistics as a process for making inferences about population parameters based on a random sample from that population.
- HSS-IC.B.6Evaluate reports based on data.
CCSS ELA · 12
- RST.9-10.7Translate quantitative or technical information expressed in words in a text into visual form (e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into words.
- RST.9-10.8Assess the extent to which the reasoning and evidence in a text support the author’s claim or a recommendation for solving a scientific or technical problem.
- RST.11-12.1Cite specific textual evidence to support analysis of science and technical texts, attending to important distinctions the author makes and to any gaps or inconsistencies in the account.
- RST.11-12.7Integrate and evaluate multiple sources of information presented in diverse formats and media (e.g., quantitative data, video, multimedia) in order to address a question or solve a problem.
- RST.11-12.8Evaluate the hypotheses, data, analysis, and conclusions in a science or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information.
- RST.11-12.9Synthesize information from a range of sources (e.g., texts, experiments, simulations) into a coherent understanding of a process, phenomenon, or concept, resolving conflicting information when possible.
- WHST.9-12.1Write arguments focused on discipline-specific content.
- WHST.9-12.2Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes.
- WHST.9-12.5Develop and strengthen writing as needed by planning, revising, editing, rewriting, or trying a new approach, focusing on addressing what is most significant for a specific purpose and audience.
- WHST.9-12.7Conduct short as well as more sustained research projects to answer a question (including a self-generated question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation.
- WHST.9-12.9Draw evidence from informational texts to support analysis, reflection, and research.
- SL.11-12.5Make strategic use of digital media (e.g., textual, graphical, audio, visual, and interactive elements) in presentations to enhance understanding of findings, reasoning, and evidence and to add interest.