Unit Overview

Currently, California formally introduces buoyancy and density in grade 8. The NGSS focus on these concepts later in high school. At this level, the goal is for students to answer the question, Will an object or substance sink or will it float? Students can apply math and design to applications of this concept, bridging the expectations from California’s standards toward the NGSS. Buoyancy and density are physical properties of a substance independent of how much of the substance is available. However, densities can be altered with changes in temperature, opening opportunities for developing skills in experimental design.

Standards

Next Generation Science Standards – Middle School (NGSS-MS):

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. Assessment boundary includes analysis of density.

Explanation: Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.

Science and Engineering:

• Analyze and interpret data to determine similarities and differences in findings.
• Science knowledge is based upon logical and conceptual connections between evidence and explanations.

Optimizing design:

• A solution needs to be tested, and then modified on the basis of the test results, in order to improve it.
• Although one design may not perform the best across all tests, identifying the characteristics of the design that performed the best in each test can provide useful information for the redesign process.
• The iterative process of testing the most promising solutions and modifying what is proposed on the basis of the test results leads to greater refinement and ultimately to an optimal solution.
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California Science Standards:

Physical Science Standards:

8a. Students know density is mass per unit volume.

8c. Students know the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced.

8d. Students know how to predict whether an object will float or sink.

Investigation and Experimentation Standards:

9a. Plan and conduct a scientific investigation to test a hypothesis.

9b. Evaluate the accuracy and reproducibility of data.

9c. Distinguish between variable and controlled parameters in a test.

9e. Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.