tlema1617 said: How are pans nonstick?

compoundchem:

Pans are usually made non-stick using Teflon, the trade name for the polymer polytetrafluoroethene (PTFE). The polymer is a long chain of repeating units, one of which is shown below. Although PTFE is the major polymer used, not all non-stick coatings are necessarily teflon; other fluoropolymers can also be used.

image

Elemental fluorine is very reactive, but within PTFE, the fluorine atoms have an electron structure that is very stable - as such, they don’t react with other atoms easily. As the carbons in PTFE are surrounded by the fluorine atoms, they are also shielded from reacting. This prevents food from sticking to the pan.

The obvious question to ask is how the slippery non-stick coating can be made to stick to the pan in the first place. The surface of the metal pan must be roughened to make it easier to stick the polymer to it; the teflon is then applied in coats, and baked on to the pan in order to ensure it remains attached. It doesn’t attach to the metal as such, but this process makes it very difficult for it to seep out of the roughened surface of the metal.

You can read more detail here. Hope that answers the question!

Teflon is non-stick not just because of its near-nonexistent reactivity, but also quite interestingly due to the electronegativity of fluorine. The electronic structure of fluorine results in carbon-fluorine bonds having a lot of covalency (electron sharing) but the biggest electronegativity in the periodic table results in one heck of a lot of polarity (uneven electron distribution). Thanks to the molecular geometry of PTFE (Teflon), all these permanent dipoles cancel each other out along the chain very effectively. These bonds are not especially amenable to having their electrons shunted around, and unlike in hydrocarbons, any transient dipoles along the bond for Van den Waals’ forces are pretty pitiful because they essentially get drowned out by the huge dipole moment. The ultimate result is that Teflon molecules don’t actually interact with other molecules or each other very effectively. They have an electron rich outer electron cloud that refuses to budge, and the electro positive core is hard to access by nucleophiles, as they are repelled by the abundant fluorine electrons. The only reason Teflon stays as a solid, is that the chains are so long that they entwine around each other. Ironically, this makes Teflon pretty hard to remove once it’s been successfully deposited onto that roughened pan, unless you heat it until it decomposes: formally, Teflon doesn’t have a melting point, and I have never found a solvent yet that will dissolve it.

(Reblogged from compoundchem)

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Please do submit questions, anything from the sciences shall be answered!

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crookedindifference:

The ultimate fate of an expanding universe

Top: Diagrams of three possible geometries of the universe: closed, open and flat from top to bottom, corresponding to a density parameter Ωwhich is greater than, less than or equal to 1. The closed universe is of finite size and, due to its curvature, traveling far enough in one direction will lead back to one’s starting point. The open and flat universes are infinite and traveling in a constant direction will never lead to the same point.

Bottom: The age and ultimate fate of the universe can be determined by measuring the Hubble constant today and extrapolating with the observed value of the deceleration parameter, uniquely characterized by values of density parameters (ΩM for matter and ΩΛ for dark energy). A “closed universe” with ΩM > 1 and ΩΛ = 0 comes to an end in a Big Crunch and is considerably younger than its Hubble age. An “open universe” with ΩM ≤ 1 and ΩΛ = 0 expands forever and has an age that is closer to its Hubble age. For the accelerating universe with nonzero ΩΛ that we inhabit, the age of the universe is coincidentally very close to the Hubble age.

(Reblogged from unravelingtheuniverse)
greentea-strawberries:

This is the diffusion (Brownian Motion) of particles  - e.g. cream in coffee. I programmed this for a Computational Physics project, in C and plotted the results in gnuplot, then animated with photoshop.

greentea-strawberries:

This is the diffusion (Brownian Motion) of particles  - e.g. cream in coffee. I programmed this for a Computational Physics project, in C and plotted the results in gnuplot, then animated with photoshop.

(Reblogged from centralscience)
realcleverscience:

smarterplanet:

Powerhouse Solar Cell Inspired by Leaf Biomimicry
A team of scientists headed up by Princeton University has achieved a whopping 47 percent increase in electricity generation from flexible plastic solar cells, simply by texturing the surface to mimic the wrinkles of a typical leaf.
Full Story: Cleantechnica
via emergentfutures:

1) Biomimicry is amazing. I love that human design is now recognizing that it has so much to learn from natural design. Especially when it can replace eco-questionable solutions with much more eco-friendly solutions - such as simply creating wrinkles on a surface as opposed to something like nano-sprays with unknown side-effects.
2) As the article notes, solar is getting very, very close to the 10-15% efficiency needed to make it competitive with traditional energy sources. And with the various solar innovations coming out, I expect we’ll hit that goal soon… and then surpass it by quite a bit. But of course, this requires research and funding. *cough*fund_science*cough*

realcleverscience:

smarterplanet:

Powerhouse Solar Cell Inspired by Leaf Biomimicry

A team of scientists headed up by Princeton University has achieved a whopping 47 percent increase in electricity generation from flexible plastic solar cells, simply by texturing the surface to mimic the wrinkles of a typical leaf.

Full Story: Cleantechnica

via emergentfutures:

1) Biomimicry is amazing. I love that human design is now recognizing that it has so much to learn from natural design. Especially when it can replace eco-questionable solutions with much more eco-friendly solutions - such as simply creating wrinkles on a surface as opposed to something like nano-sprays with unknown side-effects.

2) As the article notes, solar is getting very, very close to the 10-15% efficiency needed to make it competitive with traditional energy sources. And with the various solar innovations coming out, I expect we’ll hit that goal soon… and then surpass it by quite a bit. But of course, this requires research and funding. *cough*fund_science*cough*

(Reblogged from realcleverscience)

skaterboytae:

When a honeybee dies it releases a death pheromone, a characteristic odor that signals the survivors to remove it from the hive. This might seem a supreme final act of social responsibility. The corpse is promptly pushed and tugged out of the hive. The death pheromone is oleic acid [a fairly complex molecule, CH3(CH2)7CH=CH(CH2)7COOH, where = stands for a double chemical bond]. 

What happens if a live bee is dabbed with a drop of oleic acid?

Then, no matter how strapping and vigorous it might be, it is carried “kicking and screaming” out of the hive. Even the Queen bee, if she’s painted with invisible amounts of oleic acid, will be subjected to this indignity.

Do the bees understand the danger of corpses decomposing in the hive? Are they aware of the connection between death and oleic acid? Do they have any idea what death is? Do they think to check the oleic acid signal against other information, such as healty spontaneous movement? The answer to all these questions is, almost certainly, No. In the life of the hive there’s no way that a bee can give off detectable whiff of oleic acid other than by dying. Elaborate contemplative machinery is unnecessary. Their perceptions are adequate for their needs.

Ann Druyan & Carl Sagan, Shadows Of Forgotten Ancestors: Who Are We?, What Thin Partitions 

(Reblogged from fyeahchemistry)

expose-the-light:

The Art in Biomedical Research

1. Muscle Stem Cell Factories

Credit: FASEB 2012 Bio-Art Winner - Douglas B. Cowan

This micrograph shows cells called myoblasts attached to spherical microcarriers, which allow the growth of adult stem cells that have been isolated from skeletal muscle. The stem cells are shown in green. By combining these cells in a bioreactor, the muscle stem cells can be greatly increased in number and then separated from the myoblast “feeder” cells. The image was produced in the course of studies aimed at creating artificial “stem cell factories” and was supported by NIH funding from the National Heart, Lung and Blood Institute.

2. Scaffold for Cartilage Regeneration

Credit: FASEB 2012 Bio-Art Winner - Frank Moutos and Farshid Guilak

Due to a lack of blood vessels and other characteristics, cartilage heals very slowly. One way to accelerate natural cartilage repair and growth is to use tissue engineering, or the artificially-stimulated production of functional replacement tissue. The image shows a three-dimensionally woven biomaterial scaffold. The scaffold consists of multiple layers of resorbable fiber bundles that have been woven into a porous structure. The scaffold is then seeded with cells that grow to become new tissue as the fibers are resorbed. The fibers provide stiffness and strength in a manner that mimics native collagenous tissues such as cartilage. This work to use tissue engineering to generate replacement cartilage is supported by NIH funding from the National Institutes of Arthritis and Musculoskeletal and Skin Diseases.

3. Production of New Neurons

Credit: FASEB 2012 Bio-Art Winner - Grigori Enikolopov and Ann-Shyn Chiang

New neurons are produced from neural stem cells in several areas of the adult brain. One such area is in the hippocampus, a brain structure crucial for cognitive function. The number of neural stem cells in the hippocampus decreases over time, possibly contributing to the cognitive impairment associated with aging. When activated by extrinsic stimuli, stem cells divide and generate progenitor cells, which eventually mature into neurons and migrate into the layers above, whereas stem cells themselves undergo additional rounds of rapid divisions and convert into astrocytes, thus leaving the stem cell pool. The image depicts stem cells (green) and neuronal nuclei (red). This research to understand how the brain produces new neurons is supported by NIH through the National Institute of Mental Health and the National Institute of Aging.

4. Brain, Heart, and Lung Communication

Credit: FASEB 2012 Bio-Art Winner - Li-Hsien Lin

Both glutamate and nitric oxide play an important role in transmitting cardiovascular and respiratory signals between the brain, heart, and lung. This butterfly shaped figure is an image of a rat spinal cord showing the distribution of three types of glutamate and nitric oxide synthesizing enzymes. Understanding the action and interaction of glutamate and nitric oxide in the nervous system could lead to better treatments for cardiovascular diseases such as hypertension and heart failure. This work is supported by NIH funding from the National Heart, Lung and Blood Institute.

(Reblogged from fyeahchemistry)
(Reblogged from obsessedobsesser)

itsfullofstars:

Today at 3:44 AM eastern, SpaceX launched successfully to become the first commercial company in history to attempt to visit the International Space Station. This marks the third consecutive Falcon 9 launch success and the fifth straight launch success for SpaceX.

For more information on the mission, check out the info in the SpaceX press kit. For those on Twitter, be sure to follow @elonmusk for live updates from mission control.

This is amazing people, private space travel is one step closer (also look up the asteroid mining idea)

(Reblogged from aintwejustbigdamnheroes)
scinerds:


Explore the Human Microbiome [Interactive]

Check out the awesome interactive page over at Scientific American to learn about the micro-organisms that help us keep our bodies in good health. The photo above is a screenshot of the interactive page, so check it out!

scinerds:

Explore the Human Microbiome [Interactive]

Check out the awesome interactive page over at Scientific American to learn about the micro-organisms that help us keep our bodies in good health. The photo above is a screenshot of the interactive page, so check it out!

(Reblogged from majornerd)