Instant facts- Just add water 4

A typical pencil can draw a line 35 miles long or write about 45,000 words.
http://www.wima.org/FunFacts/tabid/69/Default.aspx

Osmosis demonstration using eggs

Remember this? Today we are going t need 2 of those, maybe more if you want to go a little further.
Today we are going to play and learn about osmosis.

Before continuing:
Cells have several transport mechanisms, in other words, several different ways to make the molecules to pass from inside to outside and vice versa. On of those mechanisms is called osmosis, and we can say for sure "that's all about concentration".

Osmosis is the movement of solvent molecules through a membrane from a region of  lower solute  concentration, to a region of higher concentration.
In other words, and considering the solvent is water, osmosis is the movement of water molecules from "in" or "out" the cell, aiming to match the concentration on both sides of the membrane.

In general we only can see a cell with a microscope. You don’t need a super microscope like electronic, a optical is enough.

In Nature there is a group of cells witch don't need a microscope to be "seen”, the eggs of species that "lay eggs." Ostrich eggs are the biggest eggs (not extinct specie), humming birds are the smallest, to "make" one ostrich egg we need 24 chicken eggs.

The egg is a cell, full of potential, to become a new being; only our frying pan or a starving predator can stop it from happen.
This cell have, like any other cell, a membrane (works as envelope for white and yolk), this membrane is double layered and is easy to observe on the blunt region where it forms a air pouch.

Let's start our demonstration. Before anything else we need to "undress" 2 eggs, you can see how here.

Ready?
Let’s go

What we need

• 2 jars with lid, big enough to place the egg inside,
• marker, to write on glass,
• water,
• 2 naked eggs,
• honey.

How to:

1. Put a "naked egg" in each jar;
2. Fill the first with water;
3. Fill the second with honey;
4. Close the two jars;
5. Label them with the marker, write on the first "H2O" or "water" and in the second "honey";
6. Place the jars in the refrigerator;
7. Wait 24 hours;
8. Take the eggs of the jars.
9. What do you see?

Observations:
The egg in the water jar looks like swollen and smooth.
The egg in the honey jar looks like wrinkled.

Why?
The white part of the egg has 90% water and the honey has only about 18%. We placed our cell (the egg) in two different environments, the water (with 100% water molecules, or close enough) and the honey (with about 18% H2O).

In the first case the water flow goes from a 100% environment to a 90% environment, from the water to the cell (egg), theoretically until the two concentrations are set at 95%, the egg swells.
In the second jar the water flows from the 90% environment to the 18% environment, from the cell to the water, theoretically until the two concentrations are set at 54%, the egg wrinkles.

At this process, where solvent molecules move (in this example H2O) to find a equilibrium concentration, in two different environments, separated by a membrane, we call osmosis.

Image:

• |X| here the outside H2O concentration match the inside concentration;
• |>X| here the concentration outside the cell/egg membrane is lower then the concentration inside it, the honey example.
• |<X| here the concentration outside the cell/egg membrane is higher then the concentration inside it, the water flask example;

Make this an experiment
Try other variables; remember to write down all your observations:

• Use water with food coloring;
• Use alcohol;
• Use salt water;
• Use Vinegar;
• Or simply, place your "honey naked egg" in a jar with water and wait another 24h, what do you think it will happen?

Sources:
http://www.victorialodging.com/recreation/birding/small-big-fast-slow
http://fisiologia.med.up.pt/Textos_Apoio/Membranas/Membranas.pdf
http://www.benefits-of-honey.com/honey-nutrition.html
Et voilá!
Play with eggs, learn from them

Enjoy!

Instant facts- Just add water 3

The major ingredient in ice cream is air
in "http://EzineArticles.com/1411527"

Black hole magic

Today we are going to do some magic!
Your restless will be amazed!

What we need:

• chose a easy cleaning surface, as always, to avoid problems,
• rubber gloves,
• metal can, any size will do
• Styrofoam, like the ones in the images.

How to:

1. Put your gloves on;
2. Make a large pile of Styrofoam;
3. Pour the acetone in the can, about 1 in high;
4. Ask your restless to set aside the quantity of Styrofoam he/she thinks to fill the can;
5. Drop the pieces into the can one by one;
6. Keep dropping;
7. The pile is finish? Grab some Styrofoam from the big pile and keep dropping;
8. If everything goes as planed the big pile will disappear before your eyes into the can, like it was a "black hole" that grabs everything around it.

Results:
Styrofoam vanish in the can!

The actors:
The acetone is an organic compound (CH3)2CO, is a highly flammable liquid with a high level of solvency. A lot of compounds dissolve on acetone, like nail polish.
Styrofoam is made of polystyrene. Manufactures use a blown agent that helps to transform the polystyrene in Styrofoam, the product this procedure originate is a highly porous and rigid polymer, with high percentage of air, trapped on porous

What happened?
In fact what happen is very easy to explain. Styrofoam is a polymer, made of several chemical units linked (like all polymers), acetone works on this links breaking them. Once the Styrofoam is made by thousands of air bubbles, all that remains at the end of the chemical reaction is: air.
Styrofoam is a very light material and with a lot of air inside, that makes it perfect o disappear with a small quantity of acetone.

After all where did the Styrofoam go?
When Styrofoam dissolves in acetone it doesn't disappear. Don’t forget  the statement "In nature, nothing is created, nothing is destroyed, everything is transformed". Polystyrene molecules continue in solution. Styrofoam solubility is very important when comes to recycling. Polystyrene in acetone solution can be extracted and used to make new materials avoiding its accumulation in sanitary landfills.

Caution:
Kids must be kept away from acetone,
Use other acetone then the nail polish remover for better results.
Verify if what you are using is really Styrofoam and isn't other similar biodegradable product

Et voilá!
It's a kind of magic!
Tcham tcham!

Enjoy!

Geyser Cola/ Mentos or Soda/ Candy

At first looks like a dangerous and silly prank, but if well done, on the right place is spectacular, and makes all adults want to be restless young minds.

Don't do this at home, chose an easy cleaning place!

What we need:

• 1 coke bottle, full,
• 1 Mentos pack,
• 1 cardboard, enough to "close" the bottle,
• 1 test tube... or a paper funnel,

How to:

1. Chose the place to this demonstration wisely, it will be messy, and you must be able to run away... fast;
2. Uncap the coke bottle;
3. Place all the Mentos (about 10) on the paper funnel, or test tube;
4. If you are using a test tube , place the cardboard on the top and turn the tube upside down;
5. If you are using the funnel close the end with the cardboard;
6. Place the tube/funnel on the bottle uncapped top;
7. Look around and chose a direction to run away;
8. Remove the card quickly, so the candies fall in the bottle.
9. Run!

"Parents friendly" alternative
You can do this on a smaller scale, without the amazing geyser but with same effect, and best of all, without the mess.

What we need:

• 1 glass,
• 1 Mentos pack,
• Coke or other carbonated drink.

How to:

1. Put the glass inside a bowl;
2. Fill half of the glass with your drink;
3. Throw 1 Mentos inside;
4. You don't need the running part.

Results:

Before any further conclusion, 

• What happens isn't a chemical reaction! its a physical phenomenum, witch results in the sudden production of carbon dioxide resulting in a massive bubbling;
•  If we look closer, Mentos surface is very rough... those irregularities are responsible for gas formation and sudden release.
• Soda is made up mostly of water and sugar.

Knowing, these 3 things, lets try to find out what happen:

Carbonic drinks, like coke and other sodas, contain, as its name indicates, dissolved carbon dioxide. This gas is in equilibrium  and under a certain pressure- that’s the key the pressure- ready to escape as soon as the pressure on the liquid surface lower. All we know that’s necessary to remove the cap of the bottle with careful, without shake the liquid, otherwise all the drink will come out the bottle.
Until you open the bottle, the gas remains in suspension on liquid, and it can expand to form bubbles.
Note that if you place the soda in a glass and submerge a toothpick on it, its surface will form bubbles immediately.

Why?
Water molecules attracted each other strongly, holding the gas bubble in a kind of water molecules net. To form a new bubble or to expand the existing bubbles the water molecules must to move away from each other. Extra energy is needed to break this surface tension! In other words the water shows resistance to soda bubble expansion.

In this demonstration Mentos candy is going to perturb the coke equilibrium, the surface tension, this allows the CO2 to escape.

How?
When you drop the Mentos on the bottle the surface tension is disturbed, and therefore the expansion and formation of new CO2 bubbles becomes possible. Mentos have thousands of micro holes on the surface those are called nucleation places- perfect places to form CO2 bubbles. As soon as Mentos touch the soda the bubble formation is initiated in its entire surface.
When all this CO2 is released from the bottle takes the liquid with it.

In conclusion:
This process depends greatly on CO2-under pressure- and on a element that disturb the tension -the element must be porous with nucleation holes), So we can conclude this demonstration can be done with any drink with bubbles like Sprite, beer, or even Red Bull.
We don’t know any other candy that works best then Mentos. They have thousands porous and heavy; they drown and don’t come out with the geyser.



Watch MithBusters movie "MythBusters - Diet Coke & Mentos":


Note that: Internet sources tells us that the use of diet coke works best because the low sugar ratio, witch delays the bubble formation

Sources:
Mentos e Coca-Cola- Ciência Hoje



Et voilá!

Enjoy!

Instant facts- Just add water 2

Pi, Greek letter (π), is the symbol for the ratio of the circumference of a circle to its diameter. Pi Day is celebrated by math enthusiasts around the world on March 14th. Pi = 3.1415926535…
in http://www.piday.org/

Control digits- Portuguese Identification Card case- ISBN numbers

Each Portuguese identification card has a digit to the right of the ID number.
Countless stories have been created around this digit, most of them myths.

Although this article is in "answers to readers" section, there isn't any particular reader asking about this using the normal channels, but it's a question often brought to the conversion.

So, what is this digit?
Jorge Buescu, degree in physics from the FCL, PhD in mathematics from the University of Warwick and Professor of Mathematics at IST (1), explain this in his book "O mistério do bilhete de identidade e outras histórias"- "The mystery of the identity and other stories".

It's important to clarify
This digit isn't the total number of people with exactly same name as you. This is a urban legend, if you don’t believe me just take a moment to think about this:
This is always a 1 digit number, i.e., the range is from 0 to 9, so, if I have 9 people exactly same name as me it's nuts to think there must be someone with 12 or 14 people with exactly same name? The control number for those people should be higher then 9.

So what is this mysterious digit?
On same book Jorge Buescu, explains that "The extra digit is (or would be, if the Portuguese authorities hadn't committed a pathetic mathematical error!) Only a control number that detects if the number of the card is correctly written", and continues to explain that the human brain can't handle with hundreds of number with many digits if they don’t have a link between them, or a pattern. That’s why this method is used, so the computer can detect errors in the numbers. What would happen if a supermarket operator makes a mistake with the barcode numbers and "... charge 200 bucks for a butter package..." it would be unthinkable.

This number, if there wasn't an error, like noted by Buescu, would be used to detect if the Identification Card Number entered in database contained errors or not. 
This system of "digits detectors" is used in several other daily things such as credit cards, the ISSN for periodicals, the ISBN for the books, there are many other cases like those, where we use a control digit.

So how it works?
Buescu uses book ISBN as an example.
This number is usually in the back of the books and each title have a unique 10 digit number. For instance the ISBN for Buescu book "O mistério do bilhete de identidade e outras histórias", Edições Gradiva from collection "Ciência Aberta", is 972-662-792-3.
To check if the sequence is correct the computer applies the following formula:

x1+2x2+3x3+ … +10x10

Where ISBN number is:

x1x2x3x4x5x6x7x8x9x10

The result, explains the author, is divisible by 11.

Try yourself:

ISBN:  972-662-792-3
(1x9+2x7+3x2+4x6+5x6+6x2+7x7+8x9+9x2+10x3)/11=
(9+14+6+24+30+12+49+72+18+30)/11=
264/11=
24

Some of you, restless minds always on alert, would say: Some of the ISBN numbers have X's! Yes you are correct, some control numbers are not digit but letters, in those cases the 10 is represented by an X, that's due to the nature of used algorithm (2).

If you have a Portuguese identification card, you can try it yourself, do the same as the ISBN numbers, but read the number from right o left, like the image.

The pathetic mathematical error is that the number 10 (or the X in ISBN numbers) was replaced by a 0, so half of the people with control digit 0 should have a X.

Sources:
(1) Buescu, Jorge. "O mistério do bilhete de identidade e outras histórias", Lisboa, Gradiva- Pulicações Lda, 2nd ed 2001
(2) motivate.maths.org/content/Calculator-fun/follow-project-suggestions

Et voilá!
Don't believe everything you ear

Enjoy!