Bad Breath Test

Standard V

Students will understand that Earth's atmosphere interacts with and is altered by the lithosphere, hydrosphere, and biosphere.

Objective 01

Describe how matter in the atmosphere cycles through other Earth systems.

Indicator a

Trace movement of a carbon atom from the atmosphere through a plant, animal, and decomposer, and back into the atmosphere.

Intended Learning Outcomes:

  1. Use Science Process and Thinking Skills .
    1. Plan and conduct experiments in which students may:
      • Identify a problem.
      • Formulate research questions and hypotheses.
      • Predict results of investigations based upon prior data.
      • Identify variables and describe the relationships between them.
      • Plan procedures to control independent variables.
      • Collect data on the dependent variable(s).
      • Select the appropriate format (e.g., graph, chart, diagram) and use it to summarize the data obtained.
      • Analyze data, check it for accuracy and construct reasonable conclusions.
      • Prepare written and oral reports of investigations
  2. Demonstrate Understanding of the Nature of Science
    1. Understand that science investigations use a variety of methods and do not always use the same set of procedures; understand that there is not just one "scientific method."
    2. Science findings are based upon evidence.

Description of Activity:

Overview

This activity could be used to introduce the section on Earth's biological systems. It is designed as a inquiry activity that will lead to a Student Designed Experiment.

Duration of Activity 50 minutes

Materials:

  • Four liters bromthymol blue solution
  • 20 beakers (100-250 ml)
  • Four liters blue colored water
  • One box of straws

Background Information:

Bromthymol blue solution is an indicator for CO2. To make the solution add 0.2 g. of Bromthymol blue powder to a two liter bottle of water and shake. Add drops of 0.1 M NaOH solution to achieve the desired blue color. Bromthymol blue powder can be ordered from any scientific supply catalog. Bromthymol blue is blue when basic, green when neutral, and yellow when acidic. Blowing into the solution will turn it green.

Teaching and Learning Strategies:

Ensure Inquiry

Students need to develop their own hypothesis, plan, procedure, and draw their own conclusions. Keep in mind that there are many ways in which to solve problems, and students will learn just as much from failures as from successes. Focus on the process rather than the finished product with this activity. Another good idea is answer students' questions with questions.

Prerequisite instruction

Before this activity begins, students should be taught the elements of a good science experiment. Bromthymol blue's properties should not be discussed prior to this activity. A basic knowledge of scientific equipment would be helpful.

Invitation to Learn:

Problem: Is this a test for bad breath?

Instructions

  1. Put students into groups of four to five, and provide each group with a beaker of bromthymol blue solution, a beaker of similarly colored blue water, and one straw per individual.
  2. Stress to the students that it is very important that they do not suck on the straws. (Scare the "science" out of them if necessary!)
  3. Tell the students that they should not share information with other groups (Just in case some smartie-pants knows immediately what Bromthymol blue indicates.).
  4. Ask two students to come to the front of the class and blow through the straws with all of their might into the beakers (one water, one Bromthymol blue). One of the solutions will turn green. Make a big deal about what terrible breath that the student has. Maybe offer some gum or a breath mint, then have them do it again with the same type of solutions.
  5. After this demonstration, ask the students to determine what happened to the two solutions. Provide all groups with plenty of access to both solutions, beakers, and straws. (You may want to have Listerine, gum, breath mints, and other items available.)
  6. Tell students that they need to follow the scientific method and write up a brief report of their findings. They may use lab notebooks for recording data and write a formal report later.

Safe Operating Procedures

  • DO NOT SUCK ON STRAWS, or taste or drink the solutions. · Wear safety glasses at all times.
  • Handle glassware carefully.
  • If solution comes in contact with skin and/or clothes, rinse off immediately.

Summary of Learning:

Assessment

A variety of assessment tools could be used in this inquiry. These are some examples of possible tools.

  • Have students research to determine that bromthymol blue is an indicator for carbon dioxide, and that carbon dioxide is produced by animals.
  • Ask students to discuss their hypotheses and results to discover that bromthymol blue is an indicator for CO2.
  • Have students write questions that could be associated with bromthymol blue.

Multiple choice questions

  1. What would be a good conclusion for the bad breath test?
    1. The solution tests for CO2.
    2. The solution tests for water vapor.
    3. The solution tests for heat.
    4. The solution tests for O2.
  2. Bromthymol blue might be a good chemical to use when testing which of the following:.
    1. The amount of acid in the rain
    2. The relationship between animals and plants
    3. The relationship between plants and water
    4. The quality of chemical reactions
  3. What was the difference between the two blue liquids?
    1. One was stronger than the other
    2. They were different temperatures
    3. One had a chemical indicator
    4. They had different concentrations of chemicals

Answers: A, A, C

Assessment Rubric

Skills

Emerging
1-2 Points
Partial Mastery
3-4 Points
Mastery
5-6 Points
Total Score__/24
Hypothesis
 None or incomplete Made prediction that is irrevelant Relevant hypothesis
Experiment Design
 Does not control variables Controls most variables Controls all variables
Conclusion
 Does not have a conclusion Conclusion not based on data. Complete conclusion based on experiment data
Working in class
 Did not pay much attention Worked most of the time Remained on-task throughout the experiment

Free Response Questions

  1. How might you improve your experiment?
  2. What helped you come to this conclusion?
  3. Could another group follow your steps and get the same answer?
  4. How might this test help you to understand relationships of animals to each other, to plants, to the atmosphere?

Peer Review

Ask atudents to write-up their procedure and have classmates try to duplicate their experiments.

Extensions:

  • The Biological Systems Interactions experiment is designed to follow this inquiry. It will reinforce some of the ideas suggested in this activity.
  • Students could also conduct their own experiments by using bromthymol blue as an indicator.