Description:

Students determine which of two solutions is more acidic by adding each to a given base. Students have to apply the process to a problem involving an alien creature. In the "Discovery" version, students design and perform the experiment.

The task assesses students' abilities to design and conduct an investigation, gather and organize data, come to a conclusion based on the data, and apply their understanding to an additional situation.

This task is designed to take students approximately 45-60 minutes to complete.

Overall Task Content Area:

Physical and Life Sciences

Specific Knowledge Areas:

Abilities necessary to do scientific inquiry

Chemical reactions

The interdependence of organisms

Performance Expectations:

• 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:

8 A SI 1: Abilities necessary to do scientific inquiry: Grades 5-8
1.2 Design and conduct a scientific investigation. Students should develop general abilities, such as systematic observation, making accurate measurements, and identifying and controlling variables. They should also develop the ability to clarify their ideas that are influencing and guiding the inquiry, and to understand how those ideas compare with current scientific knowledge. Students can learn to formulate questions, design investigations, execute investigations, interpret data, use evidence to generate explanations, propose alternative explanations, and critique explanations and procedures.

1.4 Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description — providing causes for effects and establishing relationships based on evidence and logical argument. This standards requires a subject knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge.

1.8 Use mathematics in all aspects of scientific inquiry. Mathematics is essential to asking and answering questions about the natural world. Mathematics can be used to ask questions; to gather, organize, and present data; and to structure convincing explanations.

8 B PS 1: Properties and changes of properties in matter: Grades 5-8
1.1 A substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the amount of the sample. A mixture of substances often can be separated into the original substances using one or more of the characteristic properties.

1.2 Substances react chemically in characteristic ways with other substances to form new substances (compounds) with different characteristic properties. In chemical reactions, the total mass is conserved. Substances often are placed in categories or groups if they react in similar ways; metals is an example of such a group.

8 C LS 3: Regulation and behavior: Grades 5-8
3.1 All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment.

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.

  (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:

Algebra (AL1): Understand patterns, relations and functions.

Data Analysis and Probability Standards (DAP1): Formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them.

Data Analysis and Probability Standards (DAP3): Develop and evaluate inferences and predictions that are based on data.

Problem Solving (PS2): Solve problems that arise in mathematics and in other contexts.

General Instructions to the Teacher:

This task is designed to take students approximately 45-60 minutes to complete.

Students will be working individually during this exercise.

Students should be ready to work as soon as the period begins. 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.

Materials for Acids and Bases- Alien I (Discovery Version):

The teacher will need:

• Distilled water
• Vinegar (5% solution)
• Ammonia (5% solution)
• Graduated cylinder or other metric measuring device
• Labels and a pen

Each student will need:

• 1 bag pH indicator paper strips
• 1 pH color chart
• 8 plastic measuring cups
• 1 dropper bottle Solution X
• 1 dropper bottle Alien Blood
• 1 dropper bottle Medicine A
• 1 dropper bottle Medicine B
• 1 dropper bottle Medicine C

Advance Preparation

• Prepare 5 dropper bottles for each student.
• Label bottles- "Solution X," "Alien Blood," "Medicine A," "Medicine B," "Medicine C."
• For Solution X prepare 0.1 ml 5% vinegar and 9.9ml distilled water
• For Alien Blood prepare 0.03 ml 5% ammonia and 9.97ml distilled water plus blue dye
• For Medicine A prepare 3 ml 5% ammonia and 7ml distilled water
• For Medicine B prepare distilled water
• For Medicine C prepare 5ml 5% vinegar and 6ml distilled water

Safety:

• Caution the students not to put any of the materials near their eyes or mouths.
• Caution the students not to smell the solutions.
• Determine a cleanup procedure for spills.
• 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.

Extensions/modifications:

• There are three versions of Acids and Bases Alien. In this version, the "Discovery" version, students design and perform the experiment. In the "Recipe" version, students are guided through the experiment. In the "Text" version, the student reads about an experiment conducted by another student but does not use any apparatus.