Category Archives: Chemistry Sidebar

Sidebar: National Chemistry Week 2014

Next week, from Sunday, October 19, 2014 to Saturday, October 25, 2014, is National Chemistry Week.

NCW 2014 - Candy

The theme for 2014 is “The Sweet Side of Chemistry,” a perfect theme for the days leading up to Halloween.

Have you ever wondered what kind of jobs chemists have? Here are three videos from the American Chemical Society that might give you some new ideas.

The Chemistry of Hershey’s shows what goes on behind the scene in the chemistry labs at Hershey’s. Researcher Paula Gibson says there isn’t a “typical day” and she advises that scientists should not be afraid of failure, although they just might have to eat their failures.

Candy Chemistry with Rich Hartel, Ph.D. discusses how the chemical properties of sugar helps define the products that can be made. Peeps jousting anyone?

Ice Cream Chemistry reveals that a job in food science can make you a lot of friends!

Chemistry can take you more places that you might have realized!

Sidebar: Looking More into Dissolving the Coat of M&M Candy

In case you were wondering why the colors of the M&M candy coats did not mix when water was added and they started to dissolve, I was able to find out a bit more information.

First, here’s a summary of what the experiment looks like:

Isn’t it interesting how the different colors meet and resist mixing?

Check the comments on this blog post for a lengthy discussion of why this happens.

Sidebar: An Animated Look at VSEPR Molecules

Just found this animated video that shows more molecule structures as predicted by VSEPR theory than your textbook does. It includes the shapes of molecules that contain atoms with lone pairs of electrons as well the shapes of those with only full bonds.

It may be easier for you to see the underlying patterns by seeing the full array of potential molecule shapes. Enjoy!

(Video by Ashley Jennings)

Sidebar: Mass Spectrometry

molecule-imageDid you ever wonder how chemists figure out the atomic mass units for the periodic table? The answer comes from a piece of equipment that has been central to chemical exploration:  the mass spectrometer. We will be seeing a mass spectrometer on our field trip, so let’s take a few minutes to find out more about them.

Mass spectrometers are used find out what atoms are present in a sample based on size. They are so sensitive that they can even detect differences between isotopes of the same element.

How do they work? That depends on the type of mass spectrometer, but in general they:

1. Pull apart molecules and convert all the atoms into a gas.

2. Knock off electrons and turns the atoms into ions.

3. Line up the ions and shoot them through a magnetic field. The magnetic field deflects lighter ions more than heavier ones, separating them by mass.

4. The separated ions hit a detector, which counts them.

5. The results are compared to known samples.

If you’d like to read more, there is a detailed explanation at Chem Guide.

 
Bozeman Science has a good discussion of Mass Spectrometry in this video. (Note: He starts with a discussion of Dalton, but hang in there. He will tie it into mass spectrometry fairly quickly).


Simple Explanation of the Mass Spectrometer has a cool animation of how it works. (A snooker ball is pool or billiard ball.)

Now you know where atomic mass units come from, how scientists do radiocarbon dating, how chemists figure out the chemical formula of unknown molecules, etc. A mass spectrometer is a handy and versatile machine.

Have you ever seen one? Have you ever used one? Where?

 

Sidebar: Lab 8 Update

A little secret:  Scientists often get more excited about what went wrong with an experiment than what went right, because then they get to ask, “Why?” Yes, we are weird that way.

I had some ideas about why the salting out experiment (Session I-4) might not have worked as well as it should. First I tried non-iodized salt I had at home, but that had little effect. Still no big separation between the water and the isopropyl alcohol.

Then I watched the video below. It struck me that we had probably used too little salt. I added a whole bunch of iodized salt and instantly —>

salting-out-experiment

Don’t worry, I’ll bring the supplies next week so we can do it again. See how much salt was left even after I shook it? It took a lot of salt to get this result.

If you have time, the narrator of the two videos below explains more about the process.

The video:

He also has one about floating a ball in the separate layers

Sidebar: Recipes for Endothermic and Exothermic Reactions

This week we learned about endothermic and exothermic reactions in Lesson 4. Now let’s take a look at examples of these reactions.

Reaction 1.

Materials:

  • 4 3.68 g packets Crystal Light Natural Pink Lemonade (primary ingredient citric acid)
  • Baking soda
  • Water
  • Large Styrofoam cup
  • Thermometer
  • Spoon or stirring rod

Procedure 1:

  1. In a sink, tub, or outdoors in an area that can get messy, mix the 4 packets of Crystal Light into approx. 100 mL of water in the Styrofoam cup.
  2. Take the temperature of the solution, taking care not to rest the thermometer on the bottom or side of the cup.
  3. Add about 1/3 cup baking soda.
  4. As the reaction starts to slow, take the temperature again.
  5. Adjust the amounts of ingredients if the temperature change was not apparent.

Did the temperature go up or down?

 

experiment-cup-citric

Reaction 2:

Materials:

  • 2 Tablespoons active yeast
  • Water
  • Large Styrofoam cup
  • Thermometer
  • Hydrogen peroxide (from drug store)
  • Spoon or stirring rod

Procedure 2.

  1. In a sink, tub, or or outdoors in an area that can get messy, mix the yeast  into approx. 100 mL of water in the Styrofoam cup. (You may also add a squirt of dish detergent)
  2. Take the temperature of the solution, taking care not to rest the thermometer on the bottom or side of the cup.
  3. Add about 1/3 cup hydrogen peroxide.
  4. As the reaction starts to slow, take the temperature again.
  5. Adjust the amounts of ingredients if the temperature change was not apparent.

Did the temperature go down or up?

If you chose to, leave a comment to let us know how the experiment turned out.

Science Sidebar: Kinetic Sieving or Spontaneous Stratification

This week we are going to be separating mixtures using laboratory techniques. It turns out that there are geological processes that result in the separation of particles of different sizes in nature. Depending on the field of science you belong to, this is called kinetic sieving or spontaneous stratification.

This cool video shows how sand and colored sugar separate into bands while being poured (direct link). It also talks a bit about separation of mixtures at the end.

According to Gray, Shearer and Thornton, “Kinetic sieving is so efficient in dry granular flows that in small scale experiments a layer of 100% coarse grains develops on top of a layer of 100% fines with a sharp concentration jump between them.” That is amazing!

We have assembled the apparatus shown in the video so you can also give it a try in lab.

Reference: Time-dependent solutions for particle-size segregation in shallow granular avalanches.
1. J.M.N.T Gray,
2. M Shearer and
3. A.R Thornton
Proc. R. Soc. A 8 March 2006 vol. 462 no. 2067 947-972