 The Joys of Learning

Physics and Chemistry

Measurement and Units

Aristarchus

Eratosthenes

Gabriel Mouton

Thomas Jefferson

accuracy                                mole

precision                                ampere

meter                                      kelvin

kilogram                                candela

second

Classroom Activities in Outline Form:  (Please Click on each individual Day for a more in-depth presentation of each activity.)

Day 1    Today we will illustrate the concepts of accuracy and precision by examining various distributions of darts on a target board.  We will introduce the idea of “error analysis” and relate this concept to the process of measurements made on a distribution of darts.

Homework assignment #1:  Practice on sets of numbers to distinguish between accuracy and precision.  Demonstrate understanding by drawing appropriated distributions on a target board.

Day 2    Today we will describe the role of measurement as a tool in science.  We will show the connection between measurement and math in a variety of daily activities, like cooking (cake chemistry video).

Homework assignment #2:  Get a recipe from home and identify the measurements in terms of scales and amounts used ( eg,. “cups”, “2 1/4 cups”)

Day 3    Today we will reflect further on the idea of scales as they arise in cooking, physics and chemistry.  We will identify the standard scales, and the corresponding units known as SI or metric quantities, which are used in science to define these scales:  length, time, amount as defined by meters, seconds, moles, and kilograms.

Homework assignment #3:  Today you will analyze a written text, and identify occurrence of metric or SI units.

Day 4    Today we will formally introduce the metric system (reference sheet).  All quantities of a given type in the metric system are connected by powers of ten.  This makes it easy to use worldwide.  We will learn how to convert between metric units.

Homework assignment #4  Review StairStep Diagram

Day 5  Today we will practice Metric Conversions

Homework assignment #5 Review everything you learned about measurement this week.

Day 6  More practice on Metric Conversions/

Day 7   Today we will review what we learned about measurement.  We will review the homework on metric conversion.  Finally, we will take an assessment quiz to measure our understanding.

Summary of Main ideas:  Measurement

Idea#1  Measurement is a central tool in science.

Idea#2  In science, measurement is linked to mathematics.  This makes science a quantitative endeavor.

Idea#3  The quality of a measurement (whether it is “good” or “poor”) can be quantified by using the concepts of accuracy and precision.  Accuracy describes how close a measurement is to an accepted value for that measurement.  Precision describes how well a measurement can be reproduced when made the same way on the same system.

Idea#4  There are many different “scales” to which measurement may be applied.  For example, a cup clearly describes a different sort of measurement scale than a meter stick.  In science, standard scales such as length, time, and amount have been specified.

Idea#5  Once a scale is defined (for example, length) it must be quantified by specifying a unit of measurement (for example, a unit of length of the meter).  Clearly, there are many possible units of measurement for a given scale (eg., for the length scale, possible units are meter, inch, foot, mile, furlong, etc.)  Experience has shown that the most convenient set of units is one based on powers of ten.  Such a system is provided by the Metric System.  In the Metric System, there are base units corresponding to each measurement scale.  These are the meter, kilogram, second, mole, ampere, Kelvin, and candela.

Idea#6  Following up on Idea#3 above, one realizes that no measurement is exact.  In science, the usual procedure when reporting any measurement is to specify its uncertainty (this refers to precision) and to calculate a percent error with respect to a standard reported value (this refers to accuracy.)  A measurement stated without its uncertainty is not a valid measurement.

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