The Average Atomic Mass interactive is an adjustable-size file that displays nicely on tablets such as the iPad, on Chromebooks, and on laptops and desktops. It's use on phones is at best questionable. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

 

It's a common question from students - why are the atomic mass values not whole numbers. There are of course a couple of reasons for this. First, the atomic mass values are weighted averages of all the isotopes of an element. And that's what this simulation is about. And second, the atomic mass of the isotopes of an atom are not a whole numbers (with the exception of the carbon-12 isotope).

In this simulation, students will receive mass spectrometer data from our reliable mass spec machine - Old Rickety. They will use the data to calculate the average atomic mass. The data that students receive is selected at random. We don't tell the students the element name (or it would be too easy). And of the four different levels, two of them use data from extra-terrestrial elements (which makes them impossible to look up ... since they're fictitious). 

We have added a few embellishments to the interactive to assist with visualizing, to ease the computation level, and to humor. First, we begin by showing a sample of 100 atoms of the element. They atoms are color-coded to show the two or three isotopes. The mass of the isotope is listed on the atom. (We were a bit short on space so there are no decimal places. Sorry. Your can call them mass numbers if you like.) Second, we have reported percents and atomic masses to one decimal place. This eases the computational value. And besides, that's all the precision Old Rickety is capable of. And finally, for the humor ... well, you just gotta see Old Rickety.

As mentioned, elements are selected at random so there is a low probability that two side-by-side students have the same calculations to perform. Copying is going to be minimized and helping is going to be maximized. If students miss a calculation, there are ample opportunities to make corrections. A new element is selected and they can try again.

Classrooms can simply open the Interactive and explore. Or if desired, The Physics Classroom has prepared a Show Your Work Sheet to help organize students in the process of solving each problem. The sheet can be collected and quickly checked once students have finished the activity. But more importantly, students can keep the sheet as a record of how to solve average atomic mass problems. View Show Your Work Sheet.

The Show Your Work Sheet (described above) includes a link to our Tutorial page on Average Atomic Mass. Our Tutorial pages include embedded anchors to specific locations on the page. By appending an anchor to the end of a URL, the browser will open the page and instantly scroll to the location of the anchor. For this particular page, the anchor is p5. Appending "#" + p5 to the end of the URL gets students to the location on the page with directions, examples, and advice.

Our Average Atomic Mass simulation is equipped with Task Tracker functionality. Teachers with Task Tracker subscriptions can assign the simulation and keep track of student progress. Students' progress is saved and viewable in the teachers account. Students can start the activity in class at school and finish at home. Furthermore, teachers can discard one or more of the problems.

 

 

 

There are numerous activities and resources on our website that would complement this activity. Here are a few you may be interested in:

Chemistry Tutorial: The Mole and Its Applications Chapter, Lesson 1a
This page discusses the concept of an average atomic mass and describes how to perform such calculations. 

Calculator Pad: Mole Conversions Chapter
The Calculator Pad is our go-to location for solving word problems in Chemistry. Problems have random numerals, provided automated feedback, and offer opportunities for correction. We currently have two problem sets on the topic of average atomic mass. Each has a unique emphasis and difficulty level. There are several problems in each set. The problems sets are free for use. Student progress is saved for classes that have subscribed to Task Tracker.