Mohs Hardness Scale and Phones

Youtube is flooded with phone gadget reviews, everything from "Top 10 Waterproof Cameras" to "Which Keyboard Cover to Buy". But one day as I was scrolling through the comments section of an iPhone screen protector I say a post by a very agitated individual. The comment was something like:

You stupid &^!@* why are you supporting the *!&@^ companies who make these glass protecters from beer bottles and charges us SO MUCH! They don't even WORK!

The ranting and swearing went on for some time, but the important part of the comment is:

I got this exact screen protector and when I was at the beach I brushed some sand off my phone and it scratched the @&^$# protector!

This comment really made me angry, not because of the swearing or anything, but because I understood the reason behind the scratches and it has nothing to do with the company that makes them. He might as well have said: I smashed my iPhone with a sledgehammer, now it doesn't work! Apple sucks. Here's the reason his screen got scratched.

All materials have different hardnesses. There have been various scales developed by different people but the most common and universal one is the Mohs hardness scale. It was developed to rate mineral hardness, but it can be applied to everyday materials too. The scale goes from 1 to 10 and a material can get scratched by anything equal to or harder than itself.

 Now according to this picture, glass has a hardness of around 5.5. Sand is made mostly out of quartz, which has a hardness of 7. Now is clear why the guy scratched his new phone protector when he brushed off the sand. It is simple not possible to make ordinary glass harder, so even the world's top screen protectors are no match for sand. Apple is developing sapphire glass, which is made of aluminium oxide. Aluminium oxide, aka corundum, ranks at number 9, making it immune to sand. Perhaps one day we will have sapphire glass screen protectors?

Image Citation: N.d. The Mohs Scale of Mineral Hardness. Web. 9 May 2016.

Dry Cleaning

A lot of people when they think of dry cleaning think of jets of dry cleaning gas being blown into garments with no liquid involved whatsoever. But the truth is, dry cleaning is almost the same as normal cleaning, just a different solvent is used. The machine used even resembles a household washing machine.

The key difference between dry clean and normal washing is the liquid used. Most dry cleaning industries uses tetrachloroethylene due to its superior dissolving power compared to other solvents like hydrocarbon based ones or silicone based ones. But the downside of tetrachloroethylene is that it is toxic to the environment and also a likely human carcinogen. 

Why dry clean?

Garments made of wool have two problems when washed in a normal washing machine with normal detergent. The first problem is that the wool fibers have many little hooklike flakes that cause the wool to hold together. This is usually a good thing but with excessive agitation in water the hooks make the wool stick together more and thus shrinkage occurs. The second problem is that most detergents contain enzymes that are good for dissolving grease stains. But since wool is also made of protein, the enzymes also dissolve parts of the wool leaving holes in the garment. 

Image Citations: 

N.d. Care of Sheepskin and Wool. Web. 10 May 2016. <http://home.cogeco.ca/~bhemphil/care.html>.

N.d. United Machines. Web. 10 May 2016. <http://www.laundrymachines.in/dry-cleaning-machines.htm>.

Supercooling

Most substances have a freezing point, the temperature at which a substance transitions from a liquid to a solid. However there is an effect known as supercooling in which a liquid's temperature may drop below the freezing point yet still remain a liquid. This is due to the fact that in order for a liquid to freeze, its molecules have line up into a crystal lattice. However, starting such a lattice requires a nucleation site, where a few molecules can lock together and start the freezing process. A nucleation site could be as simple as a grain of dust or a scratch on the surface of the container. But if a liquid is placed into a very clean container that does not have nucleation site, then the liquid could supercool. In the supercooled state, as soon at it is disturbed too much or it meets a particle of the frozen substance then the freezing process begins a chain reaction, leading to all of the liquid freezing at once.

Supercooling can be demonstrated in your own home using bottled distilled water.

What you need:
-A freezer
-5 or more bottles of distilled water
-Time

What you do:
1. Place a bottle of water in the freezer.
2. Check on it every 15 minutes after the first hour.
3. Wait for the time when the water has frozen.
4. Put in the other bottles of water in the freezer.
5. Take them out 15 minutes before the trial run bottle had frozen.
6. Any bottles with liquid water should be supercooled. Give it a hard whack or pour it onto an ice cube to begin the freezing process.

This makes the process sound simple, but in reality there are a lot of things that make it so that it doesn't supercool. If it doesn't work, keep trying!

Image Citation: Super Cooled Water. N.d. Http://www.askamathematician.com. Ask a Physicist. Web. 9 May 2016. <http://www.askamathematician.com/2012/11/q-could-kurt-vonegets-ice-9-catastrophy-happen/>.

Tempered Glass

The tempered glass door on my balcony recently shattered. We still don't know what exactly caused it, but that's not important. What is important is how it broke into thousands of tiny shards. These shards may cause some minor cuts, but they are way better than traditional glass which would have broken into large dagger like pieces. Another lifesaving application of this kind of glass is in car windshields where you don't want a hundred knives flying through the air in the event of a car crash. To explain why it shatters into those tiny pieces, let me first introduce you to the Prince Rupert's drop.

A Prince Rupert's drop is formed when molten glass is dripped into water. It consist of a small glass 'head' and a long 'tail'. The head is immensely strong and can withstand hammer blows easily. But as soon as the fragile tail is broken, the whole thing explodes into what is essential fine glass sand. The reason behind this is pent up stress in the drop. When the molten glass is dripped into water, the out layer cools and solidifies immediately. But the inside of the drop is still liquid. As the inside cools, it wants to contract. But since the outside glass is already a solid, it cannot contract and so enormous amounts to tension is stored inside of the glass. This property makes the head strong, since all of the molecules are tightly held a fracture cannot start here. But if the tail is broken, a small shockwave starts that releases the stored energy. This shockwave breaks the next section of glass and this section breaks another section and so on until in a fraction of a second the entire drop is broken.

Tempered glass is like a less extreme version of the Prince Rupert's drop. The newly formed glass is cooled faster than usual using cold air jets. This creates the same tension inside of the sheet of glass such that as soon as a small section is broken the entire glass plane breaks.





Image Citations: 
N.d. Prince Rupert's Drop. Web. 5 May 2016. <http://www.oberlin.edu/physics/catalog/demonstrations/mech/princerupertdrops.html>.
N.d. The American Ceramics Association. Web. 4 May 2016. <http://ceramics.org/ceramic-tech-today/video-glass-science-of-prince-ruperts-drop-captured-with-high-speed-cameras>.

Sunscreen and Sunburn

The school I go to held a school wide spring fair recently. As part of a Boy Scouts troop, I volunteered to cook and sell hotdogs for 6 hours. But when I got home, I realised I had been severely sunburned and my entire neck was red. This made me regret not putting on sunscreen. But how exactly does sunscreen work?

There are two main kinds of sunscreen, those who's chemicals reflect the sun's rays, and those that absorb the sun's rays. Reflecting ones are called physical sun screens and absorbing ones are called chemical sun screens. Before explaining further, lets talk about why you get a sunburn.

Sunburn is not caused by the heat of the sun or the visible light emitted. Instead, it is caused by ultraviolet radiation that is produced by the fusion happening in the core. This is precisely the reason why you can skill get sunburned on an overcast day. The clouds only block visible light, but the ultraviolet rays can still penetrate through. Once the ultraviolet rays hit your skin, they damage the DNA of your skin cells. This causes the body to react either by repairing the damaged cells, or if they are too damaged to be repaired, they are removed. The body attempting to remove irreparable cells causes the peeling skin associated with sunburn victims. 


Cancer risk: 
Repeated sunburn has been shown to increase the chances of developing certain types of cancer, mainly melanoma, basal-cell carcinoma and squamous-cell carcinoma. As stated previously, the ultraviolet radiation hits the skin and destroys parts of the DNA inside. Normally this damage is repaired or the cell is killed, but sometimes the cell may become cancerous and develop out of control. 




Chemical Sunscreen:
Uses one or more of the following: Oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. 

Physical Sunscreen:
Physical sunscreen contains zinc oxide or titanium dioxide.

Image Citations: 

N.d. Food and Drug Administration. Web. 27 Apr. 2016. <http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/Tanning/ucm116425.htm>.

N.d. Sammi the Beauty Buff. Web. 27 Apr. 2016. <http://www.sammithebeautybuff.com/2013/08/ingredient-controversy-oxybenzone-plus.html>.

Florescence: What is it?

Brightly coloured highlighters. Neon shirts. Things that seem to be glowing ever so slightly. These things are fluorescent, which means that the pigment that gives them their colour glows when light is shined onto them. Highlighters seem brighter than normal markers because they ARE brighter. Neon shirts look brighter because they ARE brighter. Lets take a look at how this works.

Fluorescent dyes are made of of special chemicals whose electrons can be excited by incoming light. When an electron of the dye is hit by and outside source of light, it may gain energy and go into an excited state. Here is stays for a split second, loses a tiny bit of energy due to vibration, then it falls back to the un-energized state, or ground state. But it still contains energy as it falls into the ground state, where does this energy go? This energy is transformed into a photon of light, and this escapes and is what we see when we observe fluorescence.

Most people only observe fluorescence with ultraviolet rays using a black light. But in reality, any colour of light can create fluorescence. So why do we choose ultraviolet light? The answer lies in the energy of the light. Fundamentally, electromagnetic radiation of higher frequencies such as ultraviolet light have more energy than lower frequency light such as red light. In order for something to exhibit fluorescence of a particular colour, it light of a higher frequency to push the electrons into that excited state. Green light has higher energy compared to red light but it has lower energy compared to blue light. This means that if we shine a green light on a red fluorescent dye, it will glow. But we will not get a glow if we shine the green light on a blue fluorescent dye. Why do we use ultraviolet light? Ultraviolet is higher energy compared to all visible light, so it is capable of causing all fluorescent dyes to glow. If we shines green light on a green fluorescent dye, then we will not get a glow. This is because once the electron gets excited it loses a tiny bit of energy due to vibration. This means that the light emitted will always be of lower frequency than the light absorbed.

Fluorescence vs. Phosphorescence (glow in the dark)
Fluorescence is very similar to phosphorescence, the process by which glow in the dark toys work. Both involve electrons being excited by light to higher energy levels, and both involve light being released when the fall back down. But fluorescence happens only when the electrons are constantly excited. If say the ultraviolet light is shut off, the glow goes away. But the electrons in phosphorescence do not all fall back at once so it may glow for minutes or hours after the initial light source is turned off.

This video explains this concept very well (along with some awesome visuals): 

Image Citation:
N.d. Principals of Chemistry. Web. 1 May 2016. <http://faculty.csupueblo.edu/linda.wilkes/111/3c.htm>.

HOAX: Solar Roadways

Solar roadways is an idea that proposes to exchange all of the roads and parking lots in the US with hexagonal tiles of solar panels. These solar panels will also have LEDs that can display road signals and have heaters to melt snow during the winter. The developers behind this project have gotten over 2 million dollars from crowd funding and they are asking for more backing. But this idea is simply not feasible and impractical:

-Cars will cover the parking lots during the day, when these solar panels are supposed to work

-By laying the solar panels on the ground, the efficiency is reduced to 30%

-Glass is not an effective road material, and the traction will be terrible during wet weather

-Glass is not mechanical feasible, and will soon be damaged from abrasion

-There is no way to produce enough energy from the solar panels to melt any snow that falls on it

-Just the glass needed for completing this project will cost 20 trillion dollars, 10 times the federal budget

-The money needed to wire the solar panels together will cost 1 million per mile, way to expensive to be probable

-There is no way to clearly see the LEDs during bright sunlight

So why is this unfeasible project so supported?

This is because of the “oh it will be so cool” effect. IF this was possible, then it would be awesome. IF this was possible, then it may solve some issues. But it is simply not possible. Many of the news media that support this do not have the faintest clue on and of the science that goes behind this. Even some reputable science organizations are supporting this because they have not looked closely enough at the details that need to go into this.

The following video goes into some more detail and explains some of the calculations:

Image Citation: N.d. Green Tech Media. Web. 24 Apr. 2016. <http://www.greentechmedia.com/articles/read/Department-of-Transportation-Official-Discusses-Solar-Roadways>.