Lets Electroplate This Tacky Watch In Gold And Flog It Quick.

I think I finally cracked Electrolysis today, which I'm landed about, because it's the only topic in Chem that I was totally clueless on. Thank god.

So yeah.

In electrolysis, a current is carried by both positive and negative charges. Here's what it looks like...

The negative electrode -

- is known as the cathode

- always attracts the positive molecules (which are always metals or hydrogen)

- allows the positive metals to gain a couple of electrons so they can go back to being a normal atom.

The positive electrode -

- is known as the anode

- always attracts negative molecules

- allows the negative part of a substance to loose a few electrons so it can go back to being a normal atom too.

Quite simply, opposites attract.

We use electrolysis for -

- electroplating

-on submarines so they don't rust

- and one space craft so they're light but aren't damaged on take off.

Electrolysis of aluminium is an important one I have to learn...

Bauxite is mined out of the ground and purified to make aluminium oxide. The aluminium oxide is then mixed with cryolite to bring down it's melting point, because the aluminium has to be molten to conduct the electricity. Then, the aluminium oxide and cryolite is chucked in a tank that looks like this...

The anode has to be replaced every few months, because when the oxygen is separated from the aluminium, it begins to react with the carbon in the anode and produce CO2.

At the cathode, this happens...

Al^3 + 3e > Al
In other words, the ion aluminium is given 3 extra electrons to make it normal.

At the anode, this happens...

2O^2- > O2 - 4e
Aka, the oxygen ion gets rid of four electrons.

Yay, electrolysis finished. Happy Gaby.

Stop Killing My Planet.

Another biology post here :) This one is going to be on the various way humans affect the environment. I'll probably be a bit harsh because I don't like what we're doing to our home.

Okay, so Eutrophication is when fertilisers accumulate in water and cause massive problems. Basically, some crappy farmer will fill his fields with fertilises, which we eventually run into nearby streams and ponds. The algae in these water sources simply love fertilisers, so they grow loads on the surface on the water. This means that the sun can't get through to the bottom of the stream or river or pond or whatever type of body of water it is. So the planets that live under the water can't photosynthesize without the sunlight, so they die. When the planets die, they're not oxygenating the water, so all this fishies living there have nothing to breathe. They die too, and before you know it, some idiot farmer has killed the whole pond. Not good.
Apart from killing loads of species, this makes the body of water in question look really ugly. The colour and smell of the water is disgusting and loads of animals die! Luckily, we can stop all that from happening by yelling at all farmers not to use external nutrients and by filtering the algae off the water every now and then :)

Another way humans effect the planet are our contributions to biodiversity. Biodiversity is when loads of different species live in one area together. But we're causing problems with that by over-hunting certain species and cutting down their habitats. And then lots of stuff starts to die and food chains get screwed up. And in fact, we're shooting our own feet by doing that, coz we need all those plants and stuff to make drugs and food and raw materials.
So the only ways we can fix those problems is by cloning species (imo, very silly), eating synthetic meat, regulating the use of land, protecting certain species by law, and breeding animals in captivity.

And of course, we're part of more problems. Namely, the hole in the ozone layer. Usually, the ozone layer protects us from the sun's UV rays. But not so much anymore thanks to all the water vapour we've created, the CFC's you get in deodorant and all the other pollution we get up to. And thats harming our own defences. But since that hole's been getting better, the icecaps have been melting, the global temperature has been rising and humans are more likely to get cancer.
To be honest, I don't particularly want cancer, so I think we should all do stuff to stop this hole getting any bigger. Like removing CFC's from sprays, minimising high-altitude flights and decouraging deforestation.

Another problem everyone's heard about is the greenhouse effect, or global warming. What that basically means, is that humans have been releasing too much CO2, methane, nitrogen oxide and fluorinated gases into the atmosphere. This, once again, causes tonnes of problems, like the icecaps melting, a global increase in temperature and loss of species. But, we can help solve this problem by reducing our use of fossil fuels, reducing pollutants and by saving energy.

And the final problem I have to know about is bioaccumulation. This is when a pesticide is eaten by an small animal and is then passed on up the food chain. Pesticides have really long half lives, so it's bad to have them in the food chain. Since pesticides have been in use, there's been a decrease in local bird populations and northern birds have been hugely effected because the pesticides end up in the fat they use to keep warm. The only way we can stop this happening is by cutting down on the amount of pesticides we use :)

The end, although I'll post again tonight for Chemistry :)

Who Knew Plastic Could Be So Clever?

I was wrong, my next post isn't on the reactivity series.

I chose to do Polymers and Smart Materials instead, because they kinda fit together, and now I can tick two items off my list :P

Okay then, so lets go.

Plastics are a long chain of molecules (usually monomers that are alkenes). They're often carbon based too. Polymers have double covalent bonds, which look like- C=C. These double bonds (or unsaturated bonds) open up and 'join hands'.

The easiest example is apparently Ethene becoming Polythene.

Yeah, can you believe it. That's the EASIEST. WJEC are having a laugh in my opinion.

But anyway. That diagram and everything I just discussed is polymerisation, which put simply, is the act of one thing being broken up, stuck back together and with the prefix 'poly' whacked in front. Simples.

Next thing I need to talk about is the properties of plastics and how the forces between their bonds determines those properties.

It's pretty simple.

Week forces between the bonds means the atoms can slide over each other, hence making it stretchy and have a how melting point. Which all makes sense.

And molecules with strong bonds is the exact opposite, so high melting points and no stretchiness.

Alas, I'm not finished. Smart materials, because we've all been dying to get to those, haven't we?

Basically, a smart material is aptly named. It's a clever material because it responds to changes in its environment, like light, temperature and pH. Different smart materials react in different ways, so they all have different names, and here's every little dirty secret on each of them.

Shape-memory polymers - When you heat them up, you can stretch or deform them into any shape you fancy. When it cools off, it'll stay in that shape. But if it gets knocked out of shape (in a car accident, for example), you can take it home, heat it up (with a hair-drier, for example) and it'll go back to the original shape. Which is why they'd be mighty useful to use as car bumpers.

Thermochromatic paints - Are exactly what it says on the tin. They change colour according to temperature change, so we can use them on those baby-forehead-thermometers, black-mugs-that-turn-into-a-picture and those cool sheets they show us in school.

Photochromatic materials - Are also what they say they are. (If you're an idiot, the word 'photo' is in 'photograph' and 'photosynthesis' because they both involve light), so you can correctly assume that photochromatic means that these materials will change colour according to light change. When the light hits the molecules, it breaks a bond, so the material will rearrange itself to form a different type of molecule, which just happens to be a different colour. When the light is taken away, the molecules will go back to the original formation. This is the stuff they use in the fancy varifocal sunglasses for people going blind.

Shape-memory alloys - Surprise surprise, these also do what they claim to do. They seem pretty elastic, and always return to their original shape after being heated. Scientists think these could be useful to replace tendons, and they've already been used to make bendy glasses, and to make springs that widen peoples arteries.

Hydrogels - This one kinda does what it says it does. The hydro bit is fair enough, because these substances are really absorbent and used in nappies. But last time I checked (which, fair enough, was about seven years ago when my brother was born), nappies don't have gel in them. But anyway, these hydrogels can also change according to changes in pH, temperature and infra-red radiation, which would make them useful in replacing damaged muscle tissue.

Wooo. That's the end.

Kthnxbi.