Murder Mystery: A Chemical Who-dunnit'! (Katie Robinson)

Title: Using observational skills, chemistry know-how and keen intellect, students will simulate a mock dinner party and uncover a fiendish plot of sabotage.

Standards : CA Standards - 8th Physical Science

5. Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept: a. Students know reactant atoms and molecules interact to form products with different chemical properties. e. Students know how to determine whether a solution is acidic, basic, or neutral.

  • Principle(s) Investigated: Pattern Recognition
  • Investigation and Experimentation
  • Acid and Bases
  • Graphing Collected Data

9. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:

a. Plan and conduct a scientific investigation to test a hypothesis.

b. Evaluate the accuracy and reproducibility of data.

e. Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.

NGSS

Dimension 1: Scientific and Engineering Practices

2. Developing and using models

3. Planning and carrying out investigations

4. Analyzing and interpreting data

5. Using mathematics and computational thinking

6. Constructing explanations (for science)

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Dimension 2: Cross Cutting Concepts that have Common Applications Across Fields

1. Patterns

2. Cause and effect: mechanism and explanation

4. Systems and system models

Dimension 3: Core Ideas in Four Disciplinary Areas

MS-PS1-2.

Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. [Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.] [Assessment boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.]

Materials:

* All other materials can be purchased from the market at your convenience.

Procedure:

Pre-Lab Prep

  1. Place all cups out in numbered order on wide, flat surface.
  2. Fill ALL cups about 1/2 way with water.
  3. Depending on your class size, select the following:

- cup(s) with 2 drops of Rosemary Oil

- cup(s) with a pinch of Poppy Seeds

- cup(s) with 1 drop of Yellow Food Dye

- cup(s) with a few leaves

- cup(s) with chopped pecans (or other nuts)

- cup(s) with uncooked rice

- cup(s) with a pinch of flour

- 1 or 2 cups with a small amount of Sodium Hydroxide dissolved (this is the murder weapon, record the number of the cup for your records)

- All of the rest of the cups can remain the same (nothing added to them)

**BE SURE TO NOT LET ANY STUDENTS SEE WHAT WENT INTO THE CUPS PRIOR TO THE LAB!**

Lab

QUICKWRITE or LAB SHEET

    1. Exclaim to your students that there is a FIEND among them! (be as dramatic as your temperament allows)
    2. Remind students of lab safety, rules, procedures and protocol. (read: DO NOT EAT OR DRINK ANYTHING IN LAB!)
    3. Pass out a post-it, lab sheet or laptop to record observation, rounds and results.
    4. Demonstrate how to have a "Conversation" with other party guests:
    5. Find only 1 partner per round
    6. Record each others cup number in the correct round number
    7. One student pours their contents into the others cup
    8. The student then pours about 1/2 of the cup back into their cup
    9. Invite students up to select a cup and instruct them to record their number.
    10. Allow students time to make observations about the contents of their cups
    11. Ask class to share any observations about theirs and others cup contents
    12. If an odd number of students, teacher may join the "party" so every guest as the chance to participate.
    13. Each round requires students to select a different party guest to interact with.
    14. Each guest must have 3 different "conversations" ( 1 per round).
    15. Students should record their observations about their cups' contents after each round.
    16. Once all three rounds have been completed, the teacher will add 1-2 drops of phenolphthalein to each cup
    17. Students will record their observation once the indicator has been added.
    18. The teacher will display each number and ask the students to input the other cup numbers they mixed with in order by round.
    19. The teacher or student, will circle any cup that observed a chemical reaction.
    20. The teacher will then explain that the students need to look at the class wide data to find out who the fiend is by using their data to support their accusation.
    21. Collaboratively, students will use the data to call out the suspect(s).
    22. The teacher will offer only limited guidance, but may ask students to try to acquit suspects.
    23. Once students have a suspect(s), the teacher may reveal the fiend by telling them what was in each cup and the cup numbers.
    24. Have students dump their cup contents in a designated dump site and clean up their lab station.

Student prior knowledge:

  • Students should be familiar with the indicators of chemical reactions (color, heat, light, sound, gas production,odor).
  • Students should be familiar with the idea that some substances look similar and therefore need chemical testing in order to distinguish between them.
  • Students should be familiar with lab safety, procedures and protocols.
  • Students should be familiar with taking accurate data.

Explanation:

Students are often surprised to discover how many substance look like water but are in fact completely chemically different. Therefore, it is important to expose them to substances that they may come across in their lives and teach them how to properly use these substances. It is also has boarder implications by increasing student awareness on identifying patterns in data.

The purpose of this lab is to allow students the opportunity to play detective and put their scientific observational skills to work. They will need to observe their own cups contents at well as compare that to the class as whole. Then they will need to note any changes they observe and keep accurate data. Once the lab is complete, the students will collaboratively work together using the data they collected to solve the question.

The use of the poppy seeds, rosemary oil and food dye are meant to distract students from looking for the obvious clues. They need to look at the data and back track when each person who was affected came into contact with the sodium hydroxide. This allows the students to create many hypotheses and test them out by looking at the class set of data.

Students may be already familiar with acid/base indicators or you may leave it as a mystery to be solved later in a lecture. This lab is meant to cover a broad range of science skills. It may also be used in a life science class to explain how diseases can be transmitted. Here is a link to help see the most current flu stats. (National Flu Report)

Questions & Answers:

1. How can some substances mix and not create a chemical reaction?

- There are several ways to explain this to students. First, the students can look into the idea of solutes and solvents. This allows students to understand how some substances can dissolve and create varying levels of concentration within a solution. Second, this would be a great place to talk about heat of dissolution. By explaining this, students can see that mixing chemicals will not always create an immediate change but one that can build over time. Lastly, the students can discuss the law of conservation of mass and possibly do some stiochiometry.

2. Discuss a situation in which it is necessary to identify the presence of a chemical.

- This is an important skill for a researcher to master. One instance where this would be useful would be for someone who is studying pathology. For example, a person has been admitted to the hospital with some sort of poisoning. It is the pathologists job to test the blood sample to figure out what type of poison was used. Another instance would be for a doctor to understand if two medications might react negatively if taken together. Yet another could be when a chef is trying to recreate a recipe and needs to find out what ingredients to add.

3. During this lab you had to interact with a variety of people. How can you use your lab observations and apply them to your everyday life?

- This lab is a simulation of how substances can flow through a system. In the lab, sodium hydroxide is the chemical that when the indicator is present shows how a substance can spread through a system quickly. This also can simulate how a communicable disease can spread. People interact all the time and sometimes pass on pathogens without ever showing signs.Lastly, this lab allows students to see an real world application of the scientific method as well as recognizing patterns and using data to backup claims.

Applications to Everyday Life:

Data Collection and Analysis

- Data collection is paramount when trying to support claims. Whether a person is trying to build up a preponderance of evidence, find out the answer a puzzle or even going to a murder mystery dinner party, people need the ability to look at a large body of data and try to find a correlation. It is also important for students to be able to collect accurate data. In some cases, students just need an opportunity to practice skills so they can increase the ease in which they accurately predict the outcomes based on previous experiences.

Forensic Science

- A new emerging field that many students seem to show a great amount of interest in is in the field of forensic science. With the demand on the rise, students recognize the need for a strong scientific background. In this lab, students play detective and use their ability to recognize patterns and use data to create a way to identify the origin of the chemical. Just as in the case of many forensic teams across many fields of investigation, being able to recognize chemicals based on their reaction to indicator is an important skill for students to possess.

Tracking Disease/Contamination Spread

- Just like in the movies "Ourbreak" or "Evolution", scientists are often called upon to track the progress of the spread of a certain pathogens and organisms. This happens every season with the flu and the common cold. I think this application is important because it allows students to practice how to identify movement and patterns of certain items in the natural world.

Photographs:

Please see the pictures above.

Videos:

Great for teaching about the forensic science!!!

A fun trailer to show students how important it is to track the spread of diseases.

An example to show students the reaction they can expect to see.

From the best data analyzer of all time!