Magnetism: Ferro, Para, Dia

FERRO | Ferromagnetism is the "normal" form of magnetism which most people are familiar with, as exhibited in horseshoe magnets and refrigerator magnets, for instance. It is responsible for most of the magnetic behavior encountered in everyday life. The attraction between a magnet and ferromagnetic material is "the quality of magnetism first apparent to the ancient world, and to us today," according to a classic text on ferromagnetism. Ferromagnetism is defined as the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. All permanent magnets are either ferromagnetic or ferrimagnetic, as are the metals that are noticeably attracted to them.

No interesting video clip to show. Just find your own magnet!

PARA | Paramagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field. Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability greater than unity (or, equivalently, a positive magnetic susceptibility). However, unlike ferromagnets which are also attracted to magnetic fields, paramagnets do not retain any magnetisation in the absence of an externally applied magnetic field.

Elements/compounds could be paramagnetic if they have unpaired electrons. The following are some examples of paramagnetic elements:

Aluminium Al [13] (metal)
Barium Ba [56] (metal)
Oxygen. O [8] (non-metal)
Platinum Pt [78] (metal)
Sodium Na [11] (metal)
Strontium Sr [38] (metal)
Uranium U [92] (metal)
Technetium Tc [43] (artificial)

Compounds

Many salts of the d and f transitional metal group show paramagnetic behaviour. Examples are:

Copper sulphate
Dysprosium oxide
Ferric chloride
Ferric oxide
Holmium oxide
Manganese chloride

The below video clip shows a liquid oxygen bridge suspended by a strong u-shaped magnet. This demonstrates the fact that magnetic force > gravitational force.



DIA | "This is a live frog. An object does not need to be superconducting to levitate. Normal things, even humans, can do it as well, if placed in a strong magnetic field. Although the majority of ordinary materials, such as wood or plastic, seem to be non-magnetic, they, too, expel a very small portion (0.00001) of an applied magnetic field, i.e. exhibit very weak diamagnetism. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors. This experiment was conducted at the Nijmegen High Field Magnet Laboratory."



A large black superconducting disk was cooled with liquid nitrogen. When the disk goes into the superconducting state it expels magnetic field. This is called perfect diamagnetism. If you place a magnet above the disk when it is superconducting then it will levitate. This is known as the Meissner effect.




[99% Wikipedia and YouTube.]

A collection of science jokes: Part 1

There was once 3 scientists on the beach: a biologist, a chemist, and a physicist.

The biologist said: "I want to study the coral structure of the sea". So he went into the sea never to be seen again.
The physicist said: "i want to study the physics of the sea wave".' So he went into the sea and was carried away by the current never to be seen again
The chemist took out a pen and paper and wrote down: "Both biologist and physicist are soluble in water."

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An pair of atoms are walking down a street. One says to the other "I think I've lost an electron!" "Are you sure?" said the other. "Im positive!"
Another atom finds the electron and says "I'll keep an Ion it for you"

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An atom says to a shopkeeper, "How much are these neutrons?" He replies "Oh them, they're free of charge"

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My names Bond. Ionic Bond. Taken, not shared.

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There is this farmer who is having problems with his chickens. All of the sudden, they are all getting very sick and he doesn't know what is wrong with them. After trying all conventional means, he calls a biologist, a chemist, and a physicist to see if they can figure out what is wrong. So the biologist looks at the chickens, examines them a bit, and says he has no clue what could be wrong with them. Then the chemist takes some tests and makes some measurements, but he can't come to any conclusions either. So the physicist tries. He stands there and looks at the chickens for a long time without touching them or anything. Then all of the sudden he starts scribbling away in a notebook. Finally, after several gruesome calculations, he exclaims, "I've got it! But it only works for spherical chickens in a vacuum."

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Q: What is the name of the molecule CH2O?
A: Seawater

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To end with a historical note:

In the 1980's, in an effort to increase public awareness about the importance of chemistry, the American Chemical Society posted billboards with a picture of C6H10 and the title, "It takes alkynes to make a world."

Gold is not forever with aqua regia

Concentrated hydrochloric acid or nitric acid alone cannot dissolve gold.

Aqua regia, a mixture of hydrochloric acid and nitric acid, can dissolve gold because each of its two component acids carries out a different function. The nitric acid is a good oxidising agent. Chloride ions from the hydrochloric acid from coordination complexes with the gold ions, removing them from solution. Reducing the concentration of the Au3+ ions shifts the equilibrium towards the oxidised form.

Nitric acid/hydrochloric acid with gold on either side, aqua regia with gold in the centre

Au(s) + 3NO3-(aq) + 6H+(aq) ---> Au3+(aq) + 3NO2(g) + 3H2O(l)

Au3+ (aq) + 4Cl-(a) ---> AuCl4-(aq)

Calories and so on

How much is 200 calories actually? Well, it's about 800 joules. What is a joule?

As a rough guide, 1 joule is the amount of energy required to lift a one kilogram object up by a height of 10 centimetres on the surface of the Earth.

Or

The energy required to lift a small apple (102 g) one meter against Earth's gravity.

Or

In chemical energy stored in food.

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Goodies: Celery (Apium graveolens dulce)
It is sometimes grouped as a low-calorie fibre bulk food. Not only does eating it will result in very few calories (actually negative, because digesting it requires more energy than the celery contains), it has a lot of vitamin C and fibre.


Baddies: Bacon (Sus scrofa domesticus)
Ewww.... I hate bacon. Not only does it tastes gross, it is full of fats: saturated, and worse unsaturated. Out of unsaturated fats, there are cis and trans fats (cis-trans or geometric isomerism - if you take chemistry).

cis

trans

Now it's the trans fats that we all talk about. Even your grandparents know what they are. Trans fats are bad for you! And indeed they are. It's all down to geometric isomerism. The C=C double bond in the trans isomer of the fat cause its rigidity and high density and make them hard to remove out of your body. I say they stay in your body forever (well a very long time)!

Anyways, some biology, some chemistry, some physics for you. What a happy post!

A reminder of how infinitesimal we are

The observable universe is 78 billion light years in diameter...

Don't fear if you feel lonely. We will find another civilisation in this universe... someday.