Videos of building molecules, and showing chemical reactions, with candy and toothpicks

Image of Ethyl acetate glowing for cover

Following are a couple of videos to provide students with examples of how to solve a couple of tasks in chemistry.

Building chloromethane

Using Lewis dot structures to determine how a molecule will bond.

Ester synthesis from acetic acid and ethanol

The exact mechanism is more complicated than shown here, but the basic atom movement between reactants and products is accurate.

Modeling Instruction and NGSS: Energy as a Crosscutting Concept

NGSS 3D learning logo

At the January 2017 Lasallian Symposium at St. Mary’s College in Moraga, CA, I presented a short talk describing how Modeling Instruction uses energy as a Crosscutting Concept for implementing the Next Generation Science Standards. You can download a copy of the slides from my talk here.

Video (without narration)

The periodic spiral of the elements

traditional periodic table

In working with my students’ perceptions of the periodic table, I wrapped a periodic table around a roll of paper towels. My attempt was to get them to realize that the Alkali metals are actually right next to the Noble gasses. I wasn’t sure if it was working, but in our review leading up to the finals one girl mentioned that it was a spiral–so I guess it’s helping some students.

Others have done this in a flat design (e.g. see P. Fraundorf’s page showing many great designs), but I wanted to show the idea in 3D.

Below is a video showing a periodic table spinning around on a turntable. I recommend downloading the video and using VLC Media Player, Quicktime, or some other viewer that allows you to scroll the video back and forth.

The table I used comes from ptable.com, a great resource for online and printable periodic tables.

Here are a couple other 3D ‘tables’ that email list folks have let me know about:

Excel spreadsheet for calculating molar masses and percent composition

screenshot of spreadsheet

Over a decade ago I made a Quatro-Pro  spreadsheet to make quick calculations from masses on the periodic table. Well, now Excel rules the roost, so I created a similar version  using Excel. The fundamental element of the spreadsheet is that the cell with each mass is given a name that is the symbol for the element. So, for example, instead of having to remember which cell the mass of oxygen is in (C9, in this case), you only need to type in O.

The only element that doesn’t work with its symbol is carbon. Excel will not allow a cell to be named just “C”, so I had to use “CC” instead.

Examples

  • To calculate the mass of water, just type if =h*2+o (letters can be UPPER or lower case)
  • For hydrochloric acid, type =h+cl
  • Copper nitrate: =Cu+N*2+O*6
  • Carbon dioxide =CC+O*2 (this is an example of the carbon exception from above).

Screenshot

screenshot of spreadsheet
Screenshot showing the main “working portion” of the spreadsheet.

The spreadsheet

Video overview

Physics/Chemistry of Espresso Machines: Part 1

Diagram showing how steam and water escape the water tank at two different locations.

Here’s an activity based on observing espresso machines in action. Watch the following video showing the milk steaming container (with a short sidetrack to the espresso pot).

What do you notice about the milk as it steams? Can you explain what is happening?

Diagram showing how steam and water escape the water tank at two different locations.Here are some details of how this espresso machine works:

  • The water boiling tank is filled about ¾ of the way up with water.
  • From the bottom of the water tank, a tube runs upward to the coffee holder, where the water is forced through the coffee grounds and drips down into the espresso pot.
  • At the top of the water tank, a tube leads outside to the steamer jet, which is placed in the milk steaming container.

The answers aren’t here, you need to develop them yourselves 🙂

Hints below ↓

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Notice that for the first 20-30 seconds, there are bubbles forming, but after that there are no more bubble forming.

More hints below ↓

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What is in the space above the water when the machine first starts? What is in that space after 20-30 seconds?

How close are you? The “Why” behind Percent Error

Photo of flasks with different colors

Photo of two men playing horseshoesThere’s an old saying, “Close only counts in horseshoes and hand grenades.” People would say this in response to someone saying “Well, I was close.” So, why does close count in horseshoes and hand grenades, and why is this the introduction to a science paper?

Horseshoes: If you’ve never played before (I bet most of you haven’t), the goal is to throw a horseshoe towards a pipe in the ground and have the shoe end up around the pipe. You score if the shoe is around the pipe, but you also score if your horseshoe is closer than one horseshoe away. Thus, close counts in the game of horseshoes.

I think we can all understand how close could count with a hand grenade.

“Close” in science

In science, you may run an experiment in which you make measurements and are able to compare that to some “true” value. This tends to be one of two types: Continue reading “How close are you? The “Why” behind Percent Error”

If a nucleus is full of positively charged protons, why doesn’t it fly apart?

In my physical science class this week, I realized the textbook was introducing the structure of the atom and positive and negative charges, but not answering addressing the clear question that follows the presented information is “what the heck keeps all those protons together in the nucleus?” The book does get around to the nuclear forces, but not until many chapters later when it presents forces.

Sample imageThis gap in reasoning seems consistent in many introductory chemistry/physical science books. In an attempt to bridge this gap, I have written a brief introduction to the four fundamental forces. My target audience is our 9th grade introductory physical science class, but it might also be useful in higher or lower grades.

Since my school has moved to 1:1 iPads, I formatted this document to fit well on a landscape mode (“hamburger”) iPad: 8.5″ wide by 5.5″ tall. If you want to print it, you can use a PDF reader to print two on a page, or take the Word document and edit it to your heart’s content.