« Return to AACT homepage

AACT Member-Only Content

You have to be an AACT member to access this content, but good news: anyone can join!

Need Help?

The Culminating Unknown Mark as Favorite (8 Favorites)

LAB in Identifying an Unknown, Culminating Project, Classification of Reactions. Last updated August 17, 2019.

Summary

In this lab, students identify an unknown from a list of 12 possible compounds by designing a procedure and using evidence to prove their claim. They must draw from knowledge gained throughout the year to properly develop a procedure to identify the unknown.

Grade Level

High school

Objectives

By the end of this lesson, students should be able to

  • Use their prior knowledge to design an experiment to identify an unknown.
  • Present findings of an experiment in a written and oral presentation.

Chemistry Topics

This lesson supports students’ understanding of

  • Identifying an unknown
  • Culminating project

Time

Teacher Preparation: 30 minutes

Lesson: 5–6 class periods

Materials

(Additional materials available on request)

  • Beakers
  • Bunsen burners
  • Burets
  • pH paper
  • Hot pads
  • Inoculating loops
  • Funnels
  • Distilled water
  • Tin foil
  • Plastic wrap
  • Graduated cylinders
  • Flint starters
  • Ring stands
  • Stir rods
  • Erlenmeyer flasks
  • Scoopulas
  • Pipets
  • Microplates
  • SpectroVisPlus
  • Lab Quest
  • Conductivity measurer
  • Acetic acid
  • Ascorbic acid
  • Barium chloride
  • Baking soda
  • Calcium chloride
  • Copper(II) sulfate
  • Glucose
  • Hydrochloric acid (standardized)
  • Indicators
  • Manganese(II) chloride
  • Phenyl salicylate
  • Potassium iodide
  • Silver nitrate
  • Sodium hydroxide (standardized)
  • Sucrose
  • <1.0-M Sulfuric acid
  • Vinegar
Possible unknowns:
  • Acetic acid
  • Copper(II) sulfate
  • Manganese(II) chloride
  • Sodium hydroxide
  • Sodium bicarbonate
  • Ascorbic acid
  • Glucose
  • Phenyl salicylate
  • Sucrose
  • Calcium chloride
  • Hydrochloric acid
  • Potassium iodide
  • Sulfuric acid

Safety

  • Always wear safety goggles when working in a chemistry lab.
  • Acids and bases are irritants if they come into contact with skin. Rinse immediately with water if you make contact with acid or base solutions.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

  • This resource could be used as a post-AP Chemistry exam activity.
  • When preparing the unknowns, concentrations don’t need to be more than 1.0 M.
  • Students are required to use knowledge on multiple topics: atomic theory, bonding, chemical reactions, stoichiometry, acids and bases, etc. It also encourages students to go above and beyond in demonstrating mastery.
  • Grading rubric:
Category Scoring Criteria Total Points Score

Organization
(15 points)

Information is presented in a logical sequence.

5

Speakers are organized so that all present and appropriate time.

5

Presentation appropriately cites requisite number of references.

5

Content
(55 points)

Introduction is attention-getting, lays out the problem well, and establishes a framework for the rest of the presentation.

5

Technical terms are well-defined in language appropriate for the target audience.

10

Presentation contains accurate information.

20

Material included is relevant and includes 4 of the topic concepts:

Balanced rxns Stoichiometry

Chemical naming Bonding e‑ config

Atomic structure Acids and bases

20

There is an obvious conclusion summarizing the presentation.

5

Presentation
(30 points)

Speakers maintain good eye contact with the audience. Presentation is appropriately animated (e.g. gestures, moving around, etc.).

5

Speakers use a clear, audible voice.

5

Visual aids are well prepared, informative, effective, and

not distracting.

5

Length of presentation is within the assigned time limits (4-10 min).

5

Information was well communicated.

10

Score

Total Points

100

For the Student

Lesson

Background

Over the course of this semester, you have conducted many labs that determined an unknown and its characteristics. For this lab, you will need to use all the skills you have obtained to determine the concentration of an unknown and its chemical identity. You will be given a list of possibilities but will have to use your chemistry knowledge to complete the process of elimination. After completing the experiment, you will write a report that explains your results. You will also deliver a presentation to the class.

What to do

  • Design procedure
    Requires approval by your teacher for each newly designed procedure.
  • Conduct experiment
  • Record data
  • Repeat steps 1-3 until unknown is determined
  • Write report
    This is an extended version of a conclusion because of the various steps of the procedure.
  • Present to class
    This must include a visual and verbal component. You can use PowerPoint or Prezi, write a song, design a poster, create a video, or do something else upon approval.

Requirements for Procedure:

  • At least one known chemical reaction must take place
  • At least two chemical properties must be tested
  • Concentration must be tested using Beer’s Law or a titration
  • Procedure must eliminate other possible compounds
  • Determine the unknown

Requirements for Presentation:

  • Must include at least four of the following concepts (if you think other concepts are important to address, approve it with your teacher prior to presenting):
    • Balanced reaction
    • Stoichiometry
    • Chemical naming
    • Bonding
    • Electron configuration
    • Atomic structure
    • Acids and bases
  • Contains a visual component
  • Time: 4­–10 minutes
  • Organized
  • Displays mastery of the subject

Materials

(Additional materials available on request)

  • Beakers
  • Bunsen burners
  • Burets
  • pH paper
  • Hot pads
  • Inoculating loops
  • Funnels
  • Distilled water
  • Tin foil
  • Plastic wrap
  • Graduated cylinders
  • Flint starters
  • Ring stands
  • Stir rods
  • Erlenmeyer flasks
  • Scoopulas
  • Pipets
  • Microplates
  • SpectroVisPlus
  • Lab Quest
  • Conductivity measurer
  • Acetic acid
  • Ascorbic acid
  • Barium chloride
  • Baking soda
  • Calcium chloride
  • Copper(II) sulfate
  • Glucose
  • Hydrochloric acid (standardized)
  • Indicators
  • Manganese(II) chloride
  • Phenyl salicylate
  • Potassium iodide
  • Silver nitrate
  • Sodium hydroxide (standardized)
  • Sucrose
  • <1.0-M Sulfuric acid
  • Vinegar
Possible unknowns:
  • Acetic acid
  • Copper(II) sulfate
  • Manganese(II) chloride
  • Sodium hydroxide
  • Sodium bicarbonate
  • Ascorbic acid
  • Glucose
  • Phenyl salicylate
  • Sucrose
  • Calcium chloride
  • Hydrochloric acid
  • Potassium iodide
  • Sulfuric acid

Presentation

Category Scoring Criteria Total Points Score

Organization

(15 points)

Information is presented in a logical sequence.

5

Speakers are organized so that all present and appropriate time.

5

Presentation appropriately cites requisite number of references.

5

Content

(55 points)

Introduction is attention-getting, lays out the problem well, and establishes a framework for the rest of the presentation.

5

Technical terms are well-defined in language appropriate for the target audience.

10

Presentation contains accurate information.

20

Material included is relevant and includes 4 of the topic concepts:

Balanced rxns Stoichiometry

Chemical namingBonding e‑ config

Atomic structure Acids and bases

20

There is an obvious conclusion summarizing the presentation.

5

Presentation

(30 points)

Speakers maintain good eye contact with the audience. Presentation is appropriately animated (e.g. gestures, moving around, etc.).

5

Speakers use a clear, audible voice.

5

Visual aids are well prepared, informative, effective, and

not distracting.

5

Length of presentation is within the assigned time limits (4-10 min).

5

Information was well communicated.

10

Score

Total Points

100