Students determine the mass, volume and density of a sinker, given simple tools to work with. They then apply their understanding to an additional situation. The task assesses students' abilities to make simple observations, measure volume using a graduated cylinder, measure mass using a balance, make generalized inferences from their observations, and apply their understanding to an additional situation.

This task is designed to take students approximately 10-15 minutes to complete.

Overall Task Content Area:

Physical Science

Specific Knowledge Areas:

Performance Expectations:

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

National Science Education Standards:

8 B PS 1: Properties and changes of properties in matter: Grades 5-8
1.1 A substance has characteristic properties, such as density, 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.

8 A SI 1: Abilities necessary to do scientific inquiry: Grades 5-8
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.

(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:

Number and Operations (NO2): Understand meanings of operations and how they relate to one another.

Number and Operations (NO1): Understand numbers, ways of representing numbers, relationships among numbers, and number systems.

Measurement (MEAS2): Apply appropriate techniques, tools, and formulas to determine measurements. a.

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

Connections (CNX3): Recognize and use connections among mathematical ideas.

General Instructions to the Teacher:

This task is designed to take students approximately 10-15 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 "Density of a Sinker":

At this station students should have:

• spring scale or balance
• 100 ml beaker with water
• modeling clay
• calculator
• graduated cylinder (at least 50 ml)
• 1 oz lead sinker
• string

Advance Preparation:

• Put a small piece of modeling clay in the bottom of the graduated cylinder. This will pad the graduate in case the student drops the sinker into the graduate.
• Tie a string to the lead sinker so that the students can gently lower the sinker into the graduated cylinder. This will also help them to get the sinker out of the graduate.

Safety:

• Caution the students against dropping the sinker into the graduated cylinder.
• If any glassware breaks, instruct the students NOT to attempt to clean it up themselves but to inform the instructor immediately.
• 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:

• Grade 8 task collection - Unknown Liquids
• Earth Science Task collection - Density of a Mineral