Microanalysis in Science and Engineering

Identification Using Microscopy and

Crystalline Structure

Biology and Chemistry

Contact Information

Clark George and Derek Mullican Georgec@k12tn.net

derekmullican@hotmail.comWarren County High School199 Pioneer LaneMcMinnville, TN 37110

Performance Indicators

Chemistry II Standard 1.0 Structure of Matter – 1.4 The student

will investigate the subject of ionic, covalent, metallic bonds, and attractive forces between molecules.1.5 The student will investigate the relationship of chemical bonding to the state, structure and properties of matter.

BiologyStandard 1.0 Cells – The student is able to

demonstrate appropriate use and care of compound microscopes.

Textbook Reference(s)

Biology: Principles and Explorations by Johnson and Raven, Chapters 2 & 3.

Holt, Rinehart and Winston, 2001 Addison-Wesley Chemistry by Wilbraham,

Staley, Matta, and Waterman, chapters 15 & 16. Prentice Hall, 2002

Materials Needed

Magnifying glass Dissecting microscope Light microscope Access to internet and/or electron micrograph images Sugar Salt Other crystalline compounds, i.e. sodium thiosulfate Glass of unsweetened tea Bowl of unsalted popcorn

Rubric

CATEGORY 4 3 2 1 Components of the report

All required elements are present and additional elements that add to the report (e.g., thoughtful comments, graphics) have been added.

All required elements are present.

One required element is missing, but additional elements that add to the report (e.g., thoughtful comments, graphics) have been added.

Several required elements are missing.

Question/Purpose The purpose of the lab or the question to be answered during the lab is clearly identified and stated.

The purpose of the lab or the question to be answered during the lab is identified, but is stated in a somewhat unclear manner.

The purpose of the lab or the question to be answered during the lab is partially identified, and is stated in a somewhat unclear manner.

The purpose of the lab or the question to be answered during the lab is erroneous or irrelevant.

Spelling, Punctuation and Grammar

One or fewer errors in spelling, punctuation and grammar in the report.

Two or three errors in spelling, punctuation and grammar in the report.

Four errors in spelling, punctuation and grammar in the report.

More than 4 errors in spelling, punctuation and grammar in the report.

Participation Used time well in lab and focused attention on the experiment.

Used time pretty well. Stayed focused on the experiment most of the time.

Did the lab but did not appear very interested. Focus was lost on several occasions.

Participation was minimal OR student was hostile about participating.

Procedures Procedures are listed in clear steps. Each step is numbered and is a complete sentence.

Procedures are listed in a logical order, but steps are not numbered and/or are not in complete sentences.

Procedures are listed but are not in a logical order or are difficult to follow.

Procedures do not accurately list the steps of the experiment.

Conclusion Conclusion includes whether the findings supported the hypothesis, possible sources of error, and what was learned from the experiment.

Conclusion includes whether the findings supported the hypothesis and what was learned from the experiment.

Conclusion includes what was learned from the experiment.

No conclusion was included in the report OR shows little effort and reflection.

Appearance/Organization

Lab report is typed and uses headings and subheadings to visually organize the material.

Lab report is neatly handwritten and uses headings and subheadings to visually organize the material.

Lab report is neatly written or typed, but formatting does not help visually organize the material.

Lab report is handwritten and looks sloppy with cross-outs, multiple erasures and/or tears and creases.

Special Notes

Students already have experience in using hand lenses, dissecting and light microscopes.

Students have experience in writing lab reports following this rubric.

Bond types and crystalline structures have been covered in class.

Length: two 55-minute class periods.

Crystalline structures

Examining differences in crystal forms of ionic and covalent

compounds

Engagement

Observe the glass of tea and bowl of popcorn.

Also, observe the salt shaker and the sugar bowl.

In small groups, the learner will devise a method to sweeten the tea and salt the popcorn without resorting to tasting them, using knowledge of crystalline structure, ionic and covalent bonds.

Types of Magnifying Devices

Magnifying glass Scanning

electron microscope

Light microscopeDissectingmicroscope

Ranges of Magnification

Exploration

Use the magnifying glass, dissecting microscope, and light microscope to explore differences between the two substances.

Use what you know to predict the identity of each substance based on what you see (do not taste).

Design an experiment and record your observations. Tasting allowed only at the end of your exploration.

Light microscope image of salt crystal

                                                                                                                    

                                                                                    

Light microscope image of sugar crystal

                                                                                           

Explanation

As an ionic compound, salt (NaCl) exhibits true crystal lattice structure, which can be seen as perfect cubes when magnified.

Sugar (C12H22O11), while similar to salt to the unaided eye, is a covalent compound and forms a network solid rather than a true crystal lattice. The irregularities may be observed under a microscope.

Extension or Elaboration

Use the internet to look up scanning electron microscope images of crystals of sugar, salt, and others. Ex: gemini.tntech.edu/~jbiernacki

Record observations. Use chemical properties and bond types to

explain why there are physical differences between the substances.

SEM image of salt crystal

SEM image of sugar crystal

Evaluation

Quiz over proper use of microscope. Lab practicum to identify whether substances

are ionic crystals or covalent network solids. Teacher and students use rubric to evaluate

and create formal lab report with students hypotheses, procedures, observations, and conclusions.

End Notes

Many compounds have distinctive crystalline structures that can aid in identification of the substance.

The internet offers a wealth of information and images that can help identify what is seen under magnification.