Electric and bouncy pepper

This is another version of the Jumping paper circles demonstration.
Today we will use black pepper powder.
 
What we need:

• black pepper powder,
• salt, 
• wool cloth,
• plastic fork or spoon,
• plate.

How to:

1. Mix some pepper and salt in the plate,
2. Mix well, use the fork to help you;
3. Ask your restless to separate the salt from the pepper, humm... tricky uh?;
4. Rub the fork in the cloth for 30-60sec;
5. Approach the fork and the plate, keep the fork 2,5cm away from the plate.

What happens?
The pepper jumps to the fork, leaving salt behind 

Why?
When you rub the fork with the cloth it becomes negatively charged, pepper is positively charged. That means, when you approach the fork the pepper is attracted to it, and "jumps".
The salt is also negatively charged but is slightly heavier and it doesn't jump so easily. However, if you don't keep fork distance the salt will eventually jumps, thats because the electrical attraction overcomes the weight.

See the movie:

You can learn more about this here.

Et voilá!
Bouncy pepper!

Enjoy!

Jumping paper circles

This is a classic! A electric balloon full of static electricity
What we need:

• 1 balloon,
• 1 wool cloth, you can use your hair,
• 1 paper hole puncher,
• old paper, reuse some old paper.

How to:

1. Blow the balloon;
2. Punch some holes in the paper, fold the paper several times before you use the puncher, that will give you more circles;
3. Rub the balloon in your hair or in the cloth;
4. Approach the balloon and the paper circles.

What happens?
The circles "jump and glue" to the balloon walls.

Why?


Although this is a very simple and basic demonstration some of us never stop to think about what is really going on.
The paper and the balloon are made of atoms. This atoms have a positive core surrounded by negative electrons, these move around the core.
As we saw here several times everything tends towards an equilibrium and thats why almost everything that surround us is charged with a neutral charge. Is the same as saying that the sum of its charges is 0.


Repulsion and/or attraction are only possible if the charges of both materials are different in sign. That means: repulsion and/or attraction are only possible when the objects have excess or lack of electrons and because of that have a negative or positive charge.

When the balloon was rubbed it passed from a resting state to a excited state, and therefore electrically charged(in this case with excess negative charge).

Why the balloon become charged? This was possible because the cloth and the balloon have different characteristics, one can receive electrons and the other can give them, despite they are both in a rest state to begin with. This means one is electronegative (easier to receive negative charges, balloon), and the other is electro-positive (easier to donate negative charge, hair or cloth), when two such materials are rubbed, negative charges migrate from one material to another, when are removed one is positively charged and the other negatively. If you use the hair you will find that it "will glue to the balloon."

The paper was in a rest state, neutral charged. If that is true why does it jumps to the balloon wall?

Yes, the paper was not charged.

The attraction between a neutral charged material and another can be explained using the idea of electrical dipoles, a phenomenon commonly referred to as "charge separation" (in Figure). This separation happens when neutral object is subjected to the action of other electrical charges, in this case electrical charges of the balloon, thats why the paper circles "jump" to the balloon, attracted by the negative charges.

Note: This electrical phenomenon only occurs between insulating materials, conductive materials do not have the ability to retain electric charges, as they seep through the material.

A step further:

• Change the rubbing time;
• Change the friction material (cloths can try silk, cotton, wool ...);
• Change the amount of air in the balloon.
• Make a table to record your results.

ATTENTION:
Do not forget the first rule: do not change more than one variable at a time.

sources: cienciamao.usp.br; eurekahandsonmindsonscience.blogspot.com

Et Voilá!
So simple so scientific

Enjoy!

Floating lemmons, or not

Observation:
Peeled lemons sink, unpeeled lemons float.

Why is that? Maybe the lemon peel acts like a lifebuoy, keeping the lemon above the water line.  

What we need:

• water,
• small box or a glass container, transparent,
• 1 lemon,
• your lab notebook.

 How to:

1. Fill the container with water, enough to float lemon;
2. Place the lemon inside the container;
3. Observe carefully what happens and record the results in your notebook;
4. Remove the lemon from the water;
5. Peel the lemon;
6. Place it again on the water;
7. Observe carefully what happens and record the results in your notebook.

Attention: Ask an adult o handle the knife

 

What happens?
Peeled lemon sink, unpeeled lemon float.

Why?
Notice that when the lemon was unpeeled it only sunk enough to stabilize its weight. In the picture you can see 1/4 of the lemon off water.

This is due to, at least, two factors, density and porosity.

Density, density depends on lemon weight and volume. But if we peel the lemon it becomes lighter nevertheless it sinks.

Porosity, Lemon peel is extremely porous and when placed in water, the air is trapped in these pores and can not escape, this makes the lemon float. Just enough to compensate its weight.

By simple observation we can see that the peel is made off two areas, a white and spongy one and a yellow and porous one. What if we separate this yellow and white areas?

1. Place the lemon peel in the water. Does it float?
2. Observe carefully what happens and record the results in your notebook;
3. With a knife separate the yellow section from the white section;
4. Try to place the white section in the container. Does it float?;
5. Observe carefully what happens and record the results in your notebook;
6. Now try with the yellow exterior section;
7. Observe carefully what happens and record the results in your notebook.

"The peel white section" floats! The yellow one sinks!
If you look closer you can see that the white section is very spongy, and therefore very light, ie works as a buoy.

In terms of evolution, in which only the fittest survive, we see this floating lemon as a competitive advantage, the fruits may fall from the tree, float in a water course and travel to other destinations and lands where their seeds can proliferate at will.


A step further:

• Use different citrus, like lime or orange.
• Use different fruits like  apples or bananas.
• In nature we can find different thicknesses of peels in lemons. Do the peel thickness affect the outcome?

Et voilá!
Archimedes in action.

Enjoy!

Food coloring chromatography

QUESTION: Is it possible to separate the colors of a mixture of food colorings after they have been mixed?

What we need:

• coffee filters,
• wooden skewer,
• food coloring, yellow, green and blue,
• 4 glass containers,
• markers
• 4 paper clips,water.

How to:

• Prepare the work area, chose a easy to clean zone in outside or in the kitchen, food coloring usually leave messy stains;
• Identify the bottles, assign one or two letters each color, e.g. bottle Ye (yellow) Bl (blue) Gl (green) and Mix (mixed colors), or simply ABCD, write down in your notebook which is which.
• Place 6 drops of yellow dye in the bottle Ye;
• Dilute the food coloring with 30ml water;
• Repeat this procedure for both blue and green dye;
• In the last bottle (Mix) place 2 drops of each dye and diluted as usual;
• Prepare the coffee filter, cut it in 4 identical strips;
• Put a strip of paper in each bottle, as pictured;
• Use the paper clips to keep the paper in place;
• Wait until the dye reach the top of the paper, we wait 15min, may be more or less depends on the brand of the dyes.
• After the dye reach the top of the paper remove it from the cup and put it on a horizontal surface;
• Wait until it dries;
• Observe the color patterns.

What happens?
The water climbed the paper and the food coloring dissolved on it formed patterns in the paper.
In pictures you can see we used circle and strip paper, the results were exactly the same for the used colors.

Why?
Chromatography is, as its name indicates, writing (spelling) colors (chrome) and is one of the main techniques that biochemists use to separate mixtures.

First, before attempting to answer our question, it would be necessary to state three things:

• The first is that we must have a control, in this experiment a bottle with solvent without the dye, to exclude any possible interference of anything, We have done it, but does not appear in pictures. We did not observe any color band in this “blank”.
• The second is that the solutions were made with 6 drops of dye to 30 ml water, it’s possible you might get different results when using different trademarks and/or dilutions, so in science it is very important to control everything, even the brand of reagents.
• And thirdly, we have to study the individually solution behavior so we can interpret the Mix results.

Control: No bands or spots of any color.

Green dye: Shows three colors, blue on top of the paper, a broadband green and a darker line on the base. We could observe a yellow band between the larger green band and the darker line at the base.
In the label on the bottle we can read: ”Contains yellow dye and green dye“ that way is normal o have a green and a yellow band in the paper, but where did the dark line came from? A closer look give us the answer: the darker line is a dark blue zone. Blue? Yes blue. That’s because green is the mix of the blue and yellow color. 

Yellow dye: the coffee filter paper was completely yellow. With a yellow zone more pronounced in paper, yellow is a primary color, and in the label doesn’t say anything about any addition of another type of dye.

Blue dye: We can see that the filter has three distinct zones (note the small strip in the photo), back lit we see one of the area's violet (on the color wheel this is the result of mixing blue and magenta) the second zone is blue, and the third band is a second kind of  blue, lighter and more prevalent, one is cyan, and the other is an unknown color we would probably only find out for sure using more advanced analysis techniques.

On the blue label we can read: “contains blue dye and E122”. What is this E122? The website ukfoodguide.net describe it as a carmine food coloring, the presence of this E122 may explain the violet band observed at the base of the paper.




After observing and interpreting individual results we will then look to the mix filter:

One large blue zone followed by a green one. Between them we can see a faint yellow band, in the base we can’t see the violet line or brown stain which would be expected by the presence of green dye, instead we can observe a dark indistinguishable line. Back lit we can see some violet color, but nothing conclusive. Probably this phenomenon is due to the fact that the carmine E122 and the brown present at the bottom of the paper requires more time and /or longer/ different kind of  paper to separate and become visible.

The answer to the above question is “Yes it is”. However it is necessary to improve the used technique.

A step further:

• Improve the separation method:
• Using different dilutions;
• Different filter papers;
• Bigger filter papers;
• See if you can see these bands, eventually even be surprised by other bands that become visible.

Et voilá!
A true experience!

Enjoy!

Dancing raisins in soda

QUESTION:
Will the CO2 released from a water with gas bottle be strong enough to take to the surface 6 raisins?

What we need:

• transparent glass,
• water with gas, the strongest work best,
• 6 raisins

How to:

1. Chose a easy to clean zone near the sink;
2. Fill the glass with the carbonated water, use a medium glass, if its too large the gas will escape to fast;
3. Drop the raisins in the water;
4. Observe.

What happens?
The raisins will go up and down in the water for a while.
Why?
The CO2 gas in water begins to free itself when we first open the bottle. This CO2 travels vertically through the glass until it comes into contact with the air, at this poit the gas is released into the atmosphere.

When the bubbles of carbon dioxide meet the raisins those are immediately trapped in the grape rough skin imperfections, which will do the raisin “move up” to the top. When they arrive at the top CO2 bubbles are released in the air and the raisin falls down o meet another set of CO2 bubbles and go up again, and the cycle repeats itself. This will happen until there is not enough CO2 in the water to elevate the raisins.

Make this demonstration a true experiment:

• Use vinegar and baking soda. This mix will produce CO2. Do the raisins dance? Use plain vinegar with no additives
• Use other carbonated beverages.
• What drink is most effective?
• Try to use drinks with sugar and with no sugar. Do you notice any difference in the dance?
• Repeat the experiment using plain water and effervescent Alka-Seltzer® tablets.

Remember, record all your observations so you can quickly draw conclusions. Use a timer to tell time.

Et voilá!
Raisins dancing!

Enjoy! 

Halloween vs Day of all Saints

Halloween has its origins in Celtic culture.

2000 years ago, in the territory now called Ireland, Celts feasted Samhain, this festival happen on the 1th November. This festival marked the end of the year, the winter beginning and the last harvest.
At that time some people believe that in this date the souls had their last and final chance to return to the realm of the living

In this festival people gathered and lit fires and offer sacrifices to the deceased, believing this would stop them to return. Celts also dressed in clothes made from animal skins and offer food to the dead. As time passed by the festival changed and the people started dressing as ghosts, witches and other creatures known to be malevolent, and asking food and drinks. It is thought that this was the origin of the famous "trick-or-treat".

In the Catholic Church November 1st celebrates the day of "All Saints", in Mexico, for example, is celebrated as the day of "los Muertos" (Day of the Dead).

Samhain or All Saints Day?
People celebrate Samhain (Halloween) on the night of 31 October to 1 November, but using new and present rituals adapted to each country.
The All Saints Day comes as an attempt by the Catholic Church to annul the pagan festivals of the Celtic people. This attempt, despite being brilliant (according to some experts), has not had the desired impact, and the reunion of families around the table with the goal of honoring the Saints never managed to replace Samhain with the desired success.
Today we have a kind of fusion between the two parties- the Hallowe'en and All Hallows, or Halloween and All Saints Day (Hollow has its roots in the word sanctified or holy). The current version of Samhain on the evening of October 31 to November 1, and All Saints Day on November 1, are exactly the same, honoring the dead and settle down.
actividades de outono, Halloween, mitos,
sources:
http://www.history.com
http://ancienthistory.about.com

Et voilá!
Trick-or-treat?

Enjoy!

Bernoulli demonstration- Blow the ping pong ball

Use a hair dryer and a simple ping pong ball and you can make a simple but great Bernoulli Principle demonstration- check it out here.
Today we will see the same Bernoulli Principle working in a different way


What we need:

• ping pong ball,
• plastic soda bottle, funnel,
• scissors.

How to:

1. Cut the top of the bottle, the rounded section, just like shown in picture;
2. Place the ping pong inside;
3. Fill your lungs with air;
4. Blow in the bottleneck, as many times as you want.

What happens?
Nothing! The ball stays in the plastic bottle section.

Why? 
The air you introduce in the plastic "cup" make its way leaning against the walls of the ball, as shown in the picture, causing it to rotate instead of rising.

Of course it is possible to make the ball "fly" but no lungs are able to do it.

See the video:

Et voilá!
Your Lungs can't do it!
Enjoy!