In this issue: The Mole Concept: Three Beakers Precision vs. Accuracy: Dart Game Teaching Estimation: Quantum Measurement Tutor
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Welcome to the first issue of Teacher Connection, a free online monthly newsletter to provide teachers with effective teaching techniques and helpful ideas and tools for explaining chemistry and mathematics concepts to students of all levels. The information contained within this e-newsletter is provided by Mr. Dale Holder, Quantum's Chief Academic Officer, and award-winning master teacher for over 35 years.
The Mole Concept: Three Beakers
Have you ever tried introducing the mole concept by comparing a mole to a dozen? This comparison is valid because both one dozen and one mole represent a number of objects. One dozen is just twelve objects while one mole is 6.02x10^23 but they both represent a definite discrete number. You might have a dozen eggs, a dozen books, or a dozen atoms but in each case you would have exactly the same number of objects. That number would be the familiar number of twelve. In the same way, you might have a mole of eggs, a mole of books, or a mole of atoms. Again, you would have exactly the same number of objects, the Avagadro Number, or 6.02x10^23. This is a truly vast number but it's just a number. When students recognize that a mole is a number of particles or objects it is much easier for them to understand why one mole of different substances should have different masses and different volumes.

In this discussion I use three beakers of different sizes. In a small beaker I place one dozen BB's. In a medium sized beaker I place one dozen marbles while in a large beaker I place one dozen ping-pong balls. Clearly, these have very different masses and volumes but the exact same number of objects. After viewing this demonstration it is a small jump to accept the idea that one mole of sodium, one mole of lead, and one mole of gold consist of the same number of particles but should be expected to have different masses and different volumes.

Precision vs. Accuracy: Dart Game
Students frequently have difficulty distinguishing between precision and accuracy. In fact, they frequently use them interchangeably when they are actually referring to very different concepts. To emphasize the distinction between these terms, try using an archery target, dart board, or just a hand drawn target made by drawing a bull's eye at the center surrounded by concentric circles. Drawing three imaginary bullet holes on the target sets the stage for an excellent discussion of these important terms. Precision corresponds to how closely spaced the three holes are. If they are very close together, regardless of their distance from the bull's eye, then the precision is high. The accuracy is measured by how far the holes are from the bull's eye. It's easy to move from this example to a discussion of the precision and accuracy of three consecutive measurements made using a centigram balance.

Teaching Estimation: Quantum Measurement Tutor
Having trouble teaching estimation? Most of us find it impossible to devote the necessary time to allow each student to express their personal judgment in order to develop good estimation skills. Here's a simple and effective way to use the Quantum Measurement Tutor to help develop these estimation skills that are so important in everyday life.

Ask your students to write down the name of some object that is about 10 meters in height. What they write really doesn't matter so much. The process of making a decision and committing to it is the important part. Now ask them to open the Quantum Measurement Tutor, select the meter stick as their measuring instrument, and enter 10 m as their measurement. After clicking OK go immediately to the questions menu. "About how much is 10 m?" or an alternate wording will be the very top question. When the student highlights this question and clicks OK, the Tutor will give them something to compare with their measurement. This way they can determine the accuracy of their estimate without fear of criticism. Of course this could be repeated with as many different measurements as seem useful and the Tutor never grows tired of the task.

Try this exercise with your students. Free 15-day trial for teachers and students is available. Click here.

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