Description:

Students design and conduct a scientific experiment to test which of four antacids would be most effective for neutralizing acid. They will rank the antacids in order from most effective to least effective and explain how they determined the effectiveness of each one.

This task is designed to take students approximately 45-50 minutes to complete.

Overall Task Content Area:

Physical science

Chemical reactions

• conducting investigations
• using equipment
• gathering, organizing, and representing data
• formulating conclusions from investigational data
• applying scientific principles to develop explanations and solve new problems

National Science Education Standards:<

12 A SI 1: Abilities necessary to do scientific inquiry: Grades 9-12
1.2 Design and conduct scientific investigations. Designing and conducting a scientific investigation requires introduction to the major concepts in the area being investigated, proper equipment, safety precautions, assistance with methodological problems, recommendations for use of technologies, clarification of ideas that guide the inquiry, and scientific knowledge obtained from sources other than the actual investigation. The investigation may also require student clarification of the question, method, controls, and variables; student organization and display of data; student revision of methods and explanations; and a public presentation of the results with a critical response from peers. Regardless of the scientific investigation performed, students must use evidence, apply logic, and construct an argument for their proposed explanations.

1.4 Formulate and revise scientific explanations and models using logic and evidence. Student inquiries should culminate in formulating an explanation or model. Models should be physical, conceptual, and mathematical. In the process of answering the questions, the students should engage in discussions and arguments that result in the revision of their explanations. These discussions should be based on scientific knowledge, the use of logic, and evidence from their investigation.


12 B PS 3: Chemical reactions: Grades 9-12
3.1 Chemical reactions occur all around us, for example in health care, cooking, cosmetics, and automobiles. Complex chemical reactions involving carbon-based molecules take place constantly in every cell in our bodies.

3.3 A large number of important reactions involve the transfer of either electrons (oxidation/reduction reactions) or hydrogen ions (acid/base reactions) between reacting ions, molecules, or atoms. In other reactions, chemical bonds are broken by heat or light to form very reactive radicals with electrons ready to form new bonds. Radical reactions control many processes such as the presence of ozone and greenhouse gases in the atmosphere, burning and processing of fossil fuels, the formation of polymers, and explosions.

(Use the "hot" link on the PALS home page to check the full text of related National Science Education Standards, if desired.)

National Council of Teachers of Mathematics:

DAP1: Formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them:
Grades 9-12 k. know the characteristics of well-designed studies, including the role of randomization in surveys and experiments
Grades 9-12 l. understand the meaning of measurement data and categorical data, of univariate and bivariate data, and of the term variable

PS2: Solve problems that arise in mathematics and in other contexts:
Grades 9-12

CNX3: Recognize and apply mathematics in contexts outside of mathematics:
Grades 9-12

REP1: Create and use representations to organize, record, and communicate mathematical ideas:
Grades 9-12

General Instructions to the Teacher:

This task is designed to take students approximately 45-50 minutes to complete.

Students work in a group of 5 for the first 30 minutes of the task. One member of each group will serve as an "Observer" and will also be the timer for the group. The Observer will use a different test form than the other members of the group ("Testers") who will actually be doing the testing. (See separate test forms for both "Observers" and "Testers".)

For the first 5 minutes all members of the group will decide how the testing will be done. Each person must follow the same procedures as they test the substance that they chose to use. Then, each tester will take up to 15 minutes to conduct their test. When the 15-minute testing time is complete, the group will come together for 10 minutes to exchange information. Each tester should tell the rest of the group the data that she/he recorded during their testing time. Everyone in the group must write down all of the data and information given by the other group members. At this point, 30 minutes into the testing period, the groups are broken up and each student works alone for the rest of the period answering the remaining questions in the exam sheets.

Students should be ready to work as soon as the period begins. Group assignments should be made in advance. The materials should be set out at each lab station, if possible. A central supply area, if needed, should be easily accessible. All supplies should be clearly labeled.

Safety goggles and lab aprons should be used for this task. Remind students not to taste any of the materials and to wash their hands at the conclusion of the activity.

Materials for Antacids:

At this station students should have:

• Timer or watch (for use by the "Observer")
• Substance bottles A, B, C, and D (Each substance bottle should contain an acidic solution that the students will use to determine the effectiveness of the antacids. The acidity of each substance bottle may vary.)
• Subtest kit for each tester in the group; each kit includes:
  1. four antacid containers labeled: Antacid #1, Antacid #2, Antacid #3, Antacid #4
  2. four spatulas/stirring rods
  3. universal pH indicator paper
  4. a 4-well tray

Advance Preparation:

The four substance bottles with the acidic solutions should be prepared prior to the testing period.

Safety:

• Be careful.
• Teachers and students should always exercise appropriate safety precautions and utilize appropriate laboratory safety procedures and equipment when working on science performance tasks.