entertainment

Two years in the life of a lab whiteboard

Two years ago my group and I shared a time-lapse video: A Year in the Life of a New Research Lab.  Shortly after, I picked up a new set of markers and directed the camera at our lab whiteboard. We stopped the camera last week and can now share two years in the life of our whiteboard condensed down to a 1 minute video. It contains one photo a day taken at 11:30 am for ~750 days.


 

 

Note: Some photos have been omitted due to inactivity or because there was proprietary information on the board.

By August 3, 2016 0 comments entertainment, fun

Halloween Chemistry: Cinder Toffee!



How about a spot of halloween chemistry? With nice simple explanations for the trick or treaters.

Cinder toffee!!

You’ll need:

  • Sugar
  • Golden syrup
  • A jam/jelly thermometer
  • Bicarbonate of soda
  • Grease proof paper
  • A baking tray
  • A saucepan

Safety:

The toffee mix gets very hot, be careful when handling in and make sure there’s an adult helping.


What to do:

1. Weigh out 100grams (3.5 oz) of sugar into the saucepan.
2. Add 3 tablespoons of syrup
3. Heat the mixture on a stove whilst stirring it.
4. Check the temperature of the mixture.
5. Carry on heating until it reaches 145-150oC (293-302).
6. Quickly stir in 1 teaspoon of bicarb. It will suddenly bubble up.
7. Now pour it into the baking tray, lined with grease proof paper.
8. Leave it to cool.

9. Break it all up (best done with a hammer) and enjoy!

What’s going on?
So that’s a nice simple recipe for a tasty treat but where is the science?

First off there’s the sugar and syrup. There are actually loads of different types of sugars, the stuff you put in your coffee and the granulated sugar used here is sucrose. It looks like this:

Sucrose
Golden syrup is a mixture of water, sucrose and two other sugars called fructose and glucose. They look like this:
Fructose
Glucose
Sucrose is actually made up of a fructose and glucose molecule that have been joined together.
So why do we need these three sugars to make the toffee? Well, when they are mixed all together they interfere with crystal formation. To explain how this works let’s represent each of the sugars with a different shape.
If we have one type of sugar then the molecules can pack together nice and neatly, like in the diagram. And that is exactly what happens in a crystal. But if you mix them all together they can’t form ordered patterns and so you don’t get crystals forming.
So if we tried to make the toffee with just one type of sugar then we’d end up with crystals forming which make for hard dense toffee (more like a boiled sweet). But by using 3 different sugars the crystals don’t form and instead you end up with a brittle, crunchy, glass like toffee.
Then there’s the bicarbonate of soda. You normally put this in cakes to make them rise. That’s because when you heat up the bicarb it turns to carbon dioxide gas (hence the bubbles in your cakes). The same thing happens here. When you spoon the bicarb into the hot sugar it almost instantly gets converted to carbon dioxide and causes the mixture to foam up.

Hope you enjoy the toffee and whilst you do you can find out more about the science of cinder toffer here.

By October 31, 2015 4 comments chemical education, entertainment, fun

My Extra Credit Assignment: Turn a General Chemistry Topic into a Science Museum Exhibit

When traveling, I always make a point to explore local science museums. I look for engaging exhibits that explain scientific concepts in informative and fun ways. One such exhibit at the Science Museum of Minnesota asks participants to create carbon nanotubes using foam connectors. A few friends and I used our advanced degrees to produce the example shown below (sorry for the potato quality).

The exhibit engaged people of all ages in different ways. Just behind the exhibit you can see the little guy who, moments after the picture was taken, learned all about tearing carbon nanotubes apart while deploying a rather impressive Godzilla impression.

Nanotube

Since becoming a teacher I have a new appreciation for science museum exhibits. They are a literal manifestation of Einstein’s philosophy: “If you can’t explain it to a six year old, you don’t understand it yourself.” The best exhibits make the explanation entertaining too.

So, towards the end of this spring semester when my general chemistry students requested an extra credit assignment, I knew exactly what to assign. I asked them to take one of the concepts they learned in general chemistry and create a science museum exhibit to explain it.

The assignment allowed unlimited space and budget. I was less concerned about reality and much more interested in seeing their knowledge and creativity. In the end I was blown away by their creations and would like to share a few.

Dipole-dipole Board

Dipole-dipole

The above exhibit, created by Taylor Trammell, showcases intermolecular dipole-dipole interactions. Her display contains many magnets–representing molecules–with two opposing sides, one positively charged (north pole) and one negatively charged (south pole). All of the magnets/molecules are free to rotate, except for one. Museum visitors can press a button and control the orientation of that one ‘molecule’. As it’s orientation changes, the other ‘molecules’ will reorientation to maximize dipole-dipole interactions and minimize the energy within the solvent.

A visitor could also walk up to the board with a strong bar magnet and introduce only it’s north or south pole to the magnet-filled board. That would represent the solvation of cations or anions through ion-dipole interactions. Taylor may not know it, but she found a fun way to introduce the solvent reorganization associated with Marcus Electron Transfer Theory.

Collision Theory Booth

According to the Collision Theory of Reactivity, for a chemical reaction to occur the molecules must: 1) collide, 2) have enough energy to make and break bonds, and 3) have the correct orientation when they collide. Emily Nabong demonstrates these rules of engagement through a museum exhibit that repurposes an amusement park throwing booth. Instead of milk jugs or balloons, the target is a Velcro-covered molecule. And instead of baseballs or darts, visitors throw ‘molecules’ with different geometries and Velcro coverage at the target.

If the molecule is thrown with too little momentum or too little accuracy it will not hit the board (collide). Also, if the molecule hits the board with the wrong Velcro alignment it won’t ‘stick’ (correct orientation). The ‘reaction’ will only occur if the molecule is thrown hard enough and with the right orientation.

Collision

Amorphous vs Crystalline Solids

Miranda Ave introduced an interactive “build your own solid” exhibit that demonstrates the difference between amorphous and crystalline solids. It’s comprised of two building stations. The first station offers Magnetix (below left), which have curved connectors representing bonds and metal spheres representing atoms. The second station offers Tinker Toys (below right) with only one rod length (bonds) and wood circles that connect at 90° positions (atoms).

Solids

Any structure built with the Magnetix will lack long-range order like in an amorphous solid. In contrast, a structure built with the restricted connectivity of the Tinker Toys will have a continuous, repeating pattern like those observed in crystalline solids.

Tearing apart these structures will also help demonstrate differences between amorphous and crystalline solids. Tinker Toys break apart in a ridged manner along cleavage lines while Magnetix structures break in random places.

The building stations will also be accompanied by a display with both crystalline and amorphous solids as well as an atomic picture of their structures.

Viscosity Race

Both Gabby Vega (below left) and Erum Kidwai (below right) proposed races between liquids to demonstrate differences in viscosity. They envisioned racetracks with several lanes, each labeled with a molecular structure. Museum goers would pick their ‘horse’ or lane and then watch as liquids ‘race’ down the track. Afterwards, each solution would be unveiled and the intermolecular forces dictating the viscosity and flow rates of the liquids would be explained.

Viscosity

Boyle, Lussac and Avogadro

Jessica Metzger’s museum exhibit set out to teach people about the relationship between temperature, volume, number of moles of a gas, and pressure. She proposed three different interactive stations. The first (left) contains a cylinder connected to a pressure gauge with a plunger that can be pushed or pulled. When the plunger is pushed (or pulled) and the pressure increases (or decreases), the reading on the pressure gauge will increase (or decrease) just as predicted by Boyle’s law.

The second cylinder (middle) is completely enclosed and placed on top of a heating element. When the visitors press the button a red light will turn on indicating that the chamber is being heated. As the temperature increases, the pressure will increase in accordance with Lussac’s law.

The third cylinder (right) will be taller than the other two with a lid that can move up or down without allowing gas molecules to escape. The station will be equipped with a button that, when pushed, releases compressed air into the cylinder. So, when the button is pressed, the metal lid will move up and increase the cylinder’s volume to accommodate the newly introduced gas molecules (Avogadro’s Law).

PV = nRT

Electronegativity and polarity

Carolin Hoeflich proposed an exhibit to introduce the concept of electronegativity and polarity. The exhibit includes a table with a soft foam cover and blocks representing the elements. The blocks are weighted so that electronegative elements are heavier. Museum-goers can arrange the blocks into molecular structures before dumping marbles–representing electrons–onto the table’s surface. The heavier elements will sink deeper into the foam and therefore ‘attract’ a larger number of marbles. When stepping back and looking at the structure as a whole, museum-goers will see that more marbles = more electronegativity. It’s also a fun way to visualize the dipole moment of a structure.

Electronegativity

Osmosis touch screen

Hunter Hamilton introduced a touch screen exhibit to demonstrate the principles of osmosis and osmotic pressure. Visitors will use the screen to create an environment with more or less ions (red spheres) and one of three possible ‘membrane’ options: 1) no membrane, 2) permeable to water but not ions, and 3) permeable to water and ions. Once all selections are made, the visitors presses GO and observes which direction water and ions move in their environment.

Osmosis

Le Châtelier’s Principle

Another touch screen exhibit, by Kelly Wyland, covers Le Châtelier’s Principle. Her screen displays an equilibrium with colors assigned to the reactants and products. It then asks users to predict the color change upon perturbation. After a prediction is made, the screen will show an animation that adds or removes reagents from the reaction mixture’s beaker. The color change of the solution will coincide with the concentration shifts to reach equilibrium.

LCP

Reaction Coordinate Slide

I’ve saved the largest and most interactive exhibit for last. Nathan Horvat designed an exhibit with two slides that represent an exothermic and endothermic reaction coordinate diagrams. Children (maybe adults?) would start on the platform in the middle (as reactants) and climb one of two ladders representing the activation energy to the transition state before sliding down to the landing pads (products).

The ladder/slide to the left (or right) is for an endothermic (or exothermic) reaction because the end point is higher (or lower) in energy than the starting point. One thing that I found fun about this exhibit is that, while viewing it in action, you’d likely notice more children choosing the exothermic slide because the endothermic one requires more work for less return. In a statistical fashion, the children would find the product that’s more thermodynamically favorable.

rxn coordIn closing, I want thank my students for a great semester and to share my appreciation for the students who designed these exhibits. It was a pleasure to teach them and to see them come up with such creative ideas. I hope one day, during a random science museum visit, I find one of these exhibits in action.

 

 

 

What if water had memory?

It spent some time in a homeopathSome homeopaths believe water has memory. That is how they explain the “medicinal properties” of their concoctions. Apparently people are treated even though the pill or potion may not contain a single molecule of the medicinal agent. But does water really have memory?

That depends on how you define memory. If for water it is defined as the property to have a stable state for sometime, then it has memory, just not a very good one – 50 femtoseconds is its retention time. That’s about 60 million million times shorter than the mythical goldfish’s three-second memory.

But with that “memory”, water could not retain any useful information. The memory is just its ability to form an ordered group of water molecules that can last for 50 femtoseconds. It is a bit like a crowd of people all milling around in train station – there are pockets of order where people are standing around looking at departure boards or getting a coffee. But these groups will disperse after a while. And so it is with water – there are pockets of order where the water molecules are interacting with each other and with things that are dissolved in it, but these are lost pretty quickly.

Let’s try another question. What if water had an elephant’s memory and never forgot?

In that case all the ordered pockets would hang around forever. But it wouldn’t look much like liquid water anymore. Instead it would be quite different; in fact, you would probably call it ice.

How about we try something a bit more bizarre? What if water could remember the molecules that had been dissolved in it long after the original molecules had been diluted away? And then what if that water could still act like them?

That may sound pretty outlandish, but a paper published, in the journal Nature (no less), suggested just that more than 25 years ago. Not surprisingly it proved rather controversial. Pretty soon after publication the paper was discredited, leaving no sound evidence for water being able to remember what has been in it (for any significant length of time).

But let’s ignore the evidence for a moment: what if water could retain a fond memory of long-departed solutes? In that case we’re in trouble, because, as one of my teachers used to say, “chemistry is the study of the soluble”. She meant that chemistry, mostly, involves dissolving compounds in solvents and then reacting them together to get new and interesting compounds. Water is a favourite solvent because more things dissolve in it than anything else.

However, if water can remember what had been in it then even in its purest form it would behave like it was chock full of impurities, with unpredictable results. No chemical reaction performed in water, from DNA fingerprinting to synthesis of a new drug, would ever work consistently.

But water memory isn’t just bad news for chemists – it would also affect the behaviour of your everyday tap water. One day your glass of water might have a flashback of limonene adding a pleasant hint of citrus fruit, the next it might recall capsaicin giving your water a spicy kick.

No need to worry, things wouldn’t get that far. After all you’re 70% water, life evolved in water and almost all reactions in all living things happen in water. If the primordial soup could have been influenced by non-existent chemicals then there would have been no stable environment for the life to have formed. Thus no life, no evolution and no human beings to dream up homeopathy.


Illustrations are by Martin Parker, chemistry teacher at Ampleforth College.

The Conversation

This article was originally published at The Conversation.
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By October 3, 2013 6 comments entertainment, fun