Richard Wool from the University of Delaware won the 2013 Presidential Green Chemistry Challenge Award. His research group works to develop replacements for energy and pollution intensive materials. Leather is one example. In this video he talks about ecoleather, which is made from soybean oil and natural fibers derived from chicken feathers and flax.

Goals like this are good for people who like science and want to work with material and chemistry. People have used leather for thousands of years because it has a lot of properties that make it useful and valuable. But it’s also a material with a significant environmental impact (for example the chemicals used for tanning). Coming up with more sustainable replacement materials is not always easy. So maybe some young Clear Scientists should think about how to do more of that.

Oxides form on the surfaces of metals because in the atmosphere they are in contact with oxygen. The nature of these oxides affect how we think of the metals themselves. For example everyone knows that if you leave iron laying around, it will get rusty.
The oxide layer on aluminum is very thin and adheres to the aluminum, insulating it from air and protecting it from oxidizing further. This is why we think of aluminum as a material that doesn’t corrode. (By the way, this aluminum oxide is the same compound that many gems are made of.)

Oxides form on the surfaces of metals because in the atmosphere they are in contact with oxygen. The nature of these oxides affect how we think of the metals themselves. For example everyone knows that if you leave iron laying around, it will get rusty.

The oxide layer on aluminum is very thin and adheres to the aluminum, insulating it from air and protecting it from oxidizing further. This is why we think of aluminum as a material that doesn’t corrode. (By the way, this aluminum oxide is the same compound that many gems are made of.)

Since the oxide of osmium is volatile (i.e. it evaporates) and you can smell it, osmium is seldom used for anything practical as a pure substance. However one characteristic of osmium is that it is a very dense, hard metal. For materials that need to be hard and resistant to wear, like old school pens and phonograph needles, osmium used to be used, alloyed with other metals. Like in the Osmiroid pen tip. (photo credit)

Since the oxide of osmium is volatile (i.e. it evaporates) and you can smell it, osmium is seldom used for anything practical as a pure substance. However one characteristic of osmium is that it is a very dense, hard metal. For materials that need to be hard and resistant to wear, like old school pens and phonograph needles, osmium used to be used, alloyed with other metals. Like in the Osmiroid pen tip. (photo credit)

Here on Earth we live in an atmosphere containing a reactive compound called oxygen. It’s necessary for life as we know it to exist! It also reacts with most materials. For example, metals form oxides on their outside surfaces where they touch oxygen.
The way we think of metals has a lot to do with what this oxide is like. Everyone knows that iron rusts. This is because Fe2O3 is the oxide formed on iron, which is reddish and powdery and sticks to the iron surface. On the other hand, osmium forms osmium tetroxide (“osmium with four oxygens”)  OsO4 which is volatile and evaporates into the air. Since it’s a gas you can smell it, and this is why osmium has a name that basically means “a smell.”

Here on Earth we live in an atmosphere containing a reactive compound called oxygen. It’s necessary for life as we know it to exist! It also reacts with most materials. For example, metals form oxides on their outside surfaces where they touch oxygen.

The way we think of metals has a lot to do with what this oxide is like. Everyone knows that iron rusts. This is because Fe2O3 is the oxide formed on iron, which is reddish and powdery and sticks to the iron surface. On the other hand, osmium forms osmium tetroxide (“osmium with four oxygens”)  OsO4 which is volatile and evaporates into the air. Since it’s a gas you can smell it, and this is why osmium has a name that basically means “a smell.”

The Clear Science staff recently read a couple of articles about researching a scientific basis for the widely-believed health benefits of cranberry juice. Cranberry juice is renowned for preventing urinary tract infections (UTIs), and there is evidence that it hinders E. coli attachment to cells in the urinary tract. Also, molecules found in cranberries can chelate or bind iron atoms. They do this because they have a lot of phenolic OH group on them. Lone pairs on the oxygens chelate positive metals (chelate means “hold like a claw”). This could remove extra iron from your system.
But these theories are not without counter-evidence. The residence time of cranberry components in your system after you drink them is low. Some argue that to make a real difference, they would have to stick around much longer, or you would have to drink a lot of juice.

The Clear Science staff recently read a couple of articles about researching a scientific basis for the widely-believed health benefits of cranberry juice. Cranberry juice is renowned for preventing urinary tract infections (UTIs), and there is evidence that it hinders E. coli attachment to cells in the urinary tract. Also, molecules found in cranberries can chelate or bind iron atoms. They do this because they have a lot of phenolic OH group on them. Lone pairs on the oxygens chelate positive metals (chelate means “hold like a claw”). This could remove extra iron from your system.

But these theories are not without counter-evidence. The residence time of cranberry components in your system after you drink them is low. Some argue that to make a real difference, they would have to stick around much longer, or you would have to drink a lot of juice.

We called the voltaic pile the first modern battery, because some believe that objects discovered in the 1930s (that date to the biblical era) were early batteries, called “Baghdad batteries.” These have iron rods surrounded by copper tubes, and the two metals could be separated by an electrolyte. This is the basic construction of the electrochemical cell we described earlier, with iron replacing zinc.
However, it is unknown if these objects were used this way, or for some other purpose that has not been thought of. This type of battery would have a very low potential (about 0.44 volts) and would not have a lot of power. (The voltage of the cell is the difference between the individual electrode potentials.)

We called the voltaic pile the first modern battery, because some believe that objects discovered in the 1930s (that date to the biblical era) were early batteries, called “Baghdad batteries.” These have iron rods surrounded by copper tubes, and the two metals could be separated by an electrolyte. This is the basic construction of the electrochemical cell we described earlier, with iron replacing zinc.

However, it is unknown if these objects were used this way, or for some other purpose that has not been thought of. This type of battery would have a very low potential (about 0.44 volts) and would not have a lot of power. (The voltage of the cell is the difference between the individual electrode potentials.)

By connecting zinc and copper discs separated by brine-soaked cloth, a zinc-hydrogen cell in made. Alessandro Volta studied the effect produced when metals were connected this way. One of his papers (from 1769) was called De vi attractiva ignis electrici or “On the attractive force of electric fire.” In the 1800s the concept of a battery began to be developed. By connecting several cells, stacking them, a higher voltage is produced. The word voltage comes from his name.
This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

By connecting zinc and copper discs separated by brine-soaked cloth, a zinc-hydrogen cell in made. Alessandro Volta studied the effect produced when metals were connected this way. One of his papers (from 1769) was called De vi attractiva ignis electrici or “On the attractive force of electric fire.” In the 1800s the concept of a battery began to be developed. By connecting several cells, stacking them, a higher voltage is produced. The word voltage comes from his name.

This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:
a hydrogen-forming half-reaction that happens at 0 V
a zinc-dissolving half-reaction that happens at -0.76 V
In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:

  1. a hydrogen-forming half-reaction that happens at 0 V
  2. a zinc-dissolving half-reaction that happens at -0.76 V

In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

The Clear Science Staff got an email from a producer for National Geographic a few weeks ago, and they wanted to record us explaining how a citrus battery works. (That’s us in the video BTW.) It’s for a science/comedy show that comes out next year called Duck Quacks Don’t Echo.

You put nails made out of two different metals into some acidic fruit, like an orange. If one is zinc and one is copper, you essentially make a zinc-hydrogen cell.

The battery half-reactions are 1) zinc electrodissolution (anode):

Zn → Zn2+ + 2e-

and 2) hydrogen formation (cathode):

2H+ + 2e- → H2

The zinc electrodissolution obviously happens on the surface of the zinc nail, and releases electrons. These electrons are at a low potential and want to flow to someplace at high potential. The hydrogen formation has a higher potential, and occurs when the protons (H+) in the fruit acid meet the electrons at the copper nail to form hydrogen gas (H2).

So if the two nails are connected, electrons will want to flow from the zinc nail to the copper nail. In between these two nails you place something like a cell phone. Flowing electrons are electricity, and so when they flow through the phone charger it’s electricity to charge the phone. This is how batteries work.

The Clear Science staff has been busy with battery science lately, so we haven’t had a chance to post. Perhaps talking a bit about batteries would be a good way to fill the void.

Did you know sometimes batteries are actually made of other batteries? If you cut open a 6-volt lantern battery, as they do in this video, you will find 4 smaller batteries inside. Usually these are 4 F-cell batteries (as in the video). Sometimes it is 4 D-cell batteries. An F-cell is like a D-cell but taller.

F- and D-cell batteries each have ~1.5 V potential. So that’s how they get 6 V:

  • 1.5 V x 4 = 6 V