# Scientific Measurement: Reviewing precision vs. accuracy, Measurement, and Significant Figures

#### Summary

In this introductory physics lab, students will review scientific measurement concepts that should have been covered in previous science classes. The concepts of precision and accuracy will be compared and contrasted, along with a discussion of measuring to the proper precision as dictated by a specific measuring device. Significant figures/digits (sigfigs or SDs) will also be reviewed, with a discussion about why it is necessary to use sigfigs in measurements and calculations, and a review of the rules for using proper significant figures. After a "pen and paper" review of these concepts, students will develop a procedure, in which they will use the concepts of proper precision in measurement and significant figures, to determine the density of a marble.

## Learning Goals

· differentiate between precision and accuracy

· practice using various laboratory measuring techniques

· read scales on various laboratory instruments to the proper precision

· calculate values from data gathered, using the proper number of significant digits in the final answer

## Context for Use

**Subject**: Chemistry, Physics:General Physics:Measurement/Units, Mathematical Physics

**Resource Type**: Activities:Lab Activity

**Grade Level**: High School (9-12)

## Description and Teaching Materials

· Used two different tools for measuring mass of a marble (triple beam balance and electronic scale)

· Used two different methods for measuring volume of a marble (immerse in water and measure diameter to calculate using the formula for the volume of a sphere)

· Calculate density

· Calculate percent of error from the known density of glass (density of glass = 2.6g/cm3)

This activity was specifically designed to use very little equipment (perfect for those schools that don't have a lot of equipment). If only one type of scale is available, students only need to measure mass using one method. Other objects of pure substance can be used (brass - density 8.47g/cm3, aluminum - density 2.64g/cm3, copper - density 8.94g/cm3, steel - 7.86g/cm3), but marbles are cheap and easy to come by!

Students will answer some analysis questions at the conclusion of the lab and the day after completing the lab we will have a discussion in class about the scientific method and possible sources of error in this particular lab. Pre-Lab (Acrobat (PDF) 44kB Sep18 08) Data Tables and Analysis Questions (Acrobat (PDF) 19kB Sep18 08)

## Teaching Notes and Tips

## Assessment

· Evaluate pre-lab work for correct answers (see attachment)

· Observe students as they are completing the lab - look for independence, proper scientific methodology, proper use of laboratory equipment, cooperation and collaboration within the group

· Participation in the post-lab discussion

· Evaluate analysis for correct calculations and insight into potential sources of error (see attachment)

## Standards

Strand: HISTORY AND NATURE OF SCIENCE

Sub-Strand: Scientific Inquiry.

Standard: The student will design and conduct a scientific experiment

Benchmarks:

The student will apply mathematics and models to analyze data and support conclusions.

The student will identify possible sources of error and their effects on results.