Floating pin

Another demonstration. So simple but so interesting

What we need:

• straight pins,
• water,
• toilet paper,
• bowl.

How to:

1. Fill the bowl with water;
2. Wait a few seconds until the water stop moving;
3. Can you place a straight pin floating in the water? Try it;
4. What happened?
5. Try a second pin.
6. Place the pin on the top of  a piece of toilet paper;
7. Place both things in the water, very carefully and gently
8. Wait a few seconds.

What happens?
The paper sinks, the straight pint floats.

Why? 

Surface tension, that's the answer.

When we place the pin in the water, without using the paper, it immediately sinks, its weight is too high for the area it occupies, ie is very dense.

The paper, by contrast have much area for the weight, in fact it doesn't sink, actually it soaks, in other words water molecules fill the paper pores in it's porous structure and fill the voids in the web cellulose paper. this way the paper becomes heavier and sinks.

Surface tension is responsible for what one might call "skin."

The water surface is formed by a barrier of water molecules. This barrier is what allows insects to land on water, the soap bubbles to exist, and the pin does not sink.


The first pin sinks because it doesn't start from a position of equilibrium and rest, unlike the second which is resting on the paper. The paper when sinks exerts sufficient force on the skin of the water to bend it but not to break it, and the pin floats.

Et voilá!
It's magic! No, it's science!

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!

Science Magic Tricks for everyone

Today, we bring you a video, from youtube I found this video really cool.

This video bring us 10 magic tricks we can do in a party to stun your friends

Magic tricks list:

1. Light a candle without touch the wick;
2. Balance a soda can on a table;
3. Don't break the plate;
4. Bossy hand;
5. The mysterious blast;
6. Stubborn finger;
7. The ball that returns home;
8. Money mood;
9. Acrobatic matches

NOTE: Never play with fire when you are alone!

Let's check out the real thing, during the week we will see the science behind this:

Et voilá!
It will be amazing!

Enjoy!

Floating grape- density matters

This is another demonstration of density, your restless will love this floating grapes.

Density is what does float in the air, ice cubes float on drinks and stones "drop dead" in the bottom of the lake.
We are going to make a grape to float on a glass with water.

What we need:

• 3 transparent cups,
• tape,
• pen,
• measuring cup,
• water,
• sugar,
• 3 grapes,
• tablespoon,
• paper sheet.

How to:

1. With the pen, the paper and the tape, make 3 labels for the 3 cups- Cup1 Cup2 Cup3;
2. Fill the measuring cup with water;
3. Add sugar until the solution is saturated, it will be saturated when some of the sugar, not many, remains on bottom, even after you mix it well with the spoon;
4. Fill the Cup1 with tap water;
5. Place a grape inside, what happens?;
6. Fill the Cup2 with the sugar solution;
7. Place another grape on the cup, what happens?;
8. Now, fill 1/2 of the Cup3 with the sugar solution;
9. With careful fill the rest of the Cup3 with tap water. The best way to do this is to use a spoon. Place it inside the cup, without touching the sugar solution, let the water drain along the spoon, as we saw here.
10. Place a grape inside the cup. What happens now?

Why?
The grape is denser then the water, so it sinks.
The sugar solution is denser then grape, so the grape floats. But the sugar water is denser then the tap water, when we place this 2 liquids in layers, the grape its trapped between the layers and floats.
 
If you prepare the sugar solution several hours before use it, the difference between the 2 are imperceptible, and really looks "a kind of magic";

Make this a experiment, try to use salt or substitute grapes for raisins... What happened? Keep your results in a log.
 
Et Voilá!
It's a kind of magic...

Enjoy!

Rainbow in a jar- density column

Sometimes the simplest things are the funniest. This demonstration shows multicolored layers in a jar without using much "chemistry". The final result is called "density column" because it allow us to make a pile with liquids with different densities, like we saw here.

In this project we are going to use sugar solutions with different concentrations. Those will form layers, the less dense (more diluted) at the top, the most dense (concentrated) at the bottom of the glass

We will need:

• sugar,
• water,
• food coloring,
• tablespoon,
• 5 transparent plastic cups, you can use flasks or glass cups but they must be transparent.

How to:

• Align the 5 cups on the table;
• Add 1 tablespoon of sugar in the first glass, 2 on the second, 3 on the  third... and so on, leave the fifth empty for now;
• Add 3 water tablespoons (about 45 ml) to the first 4 cups;
• Mix, homogenize the solution, if the sugar does not dissolve completely in any of the glasses add another tablespoon of water to all the glasses,
• Add 2-3 drops of red food coloring first glass, use yellow on the second, green on the third, and blue on the fourth;
• Mix again;
• Now let’s set up our rainbow. First the denser solution (more concentrated), in this demonstration is the blue with 4 sugar tablespoons. Fill 1/4 of the fifth glass with the blue solution;
• Carefully place the green solution on top of blue. The best way to do this is to put the tablespoon inside the glass, without touching the blue solution, and allow the green solution to flow along the spoon;   
• Repeat the procedure to all the solution in this order: Blue (done), Green (done), Yellow and Red. Each solution must occupy 1/4 of the glass.

Note:
If you don't succeed at the first try don't quit, try again. It’s hard to do it right without training.
There is no problem if you drink it, its only sugar water.

To make this demonstration a experiment try:

• To use flavored food coloring, what happens?
• To use water with different temperatures? Does this have any influence in the experience? How? Be careful with burns.
•  What happens if we disturb the equilibrium of the layers? try to use a toothpick and touch 2 or more layers with it.

Et Voilá!
Multicolored drinks, like witch potions.

Enjoy!

Lava in a drinking glass

Today we are going to do a very simple demonstration. Although simple produces spectacular effects, and that’s what our young restless minds like. Let’s simulate lava in a glass.

We will need:

• drinking glass, the wide and low work best,
• 1 / 4 cup vegetable oil,
• 1 teaspoon of salt,
• water,
• food colouring (optional) can be any colour, but the lava is red:).

How to:

1. Fill the glass with 3 / 4 water;
2. Add 5 drops of food colouring; 
3. Throw, slowly and gently, the vegetable oil in the cup. See how the oil floats on top;
4. Sprinkle the salt over the oil; 
5. Watch the lava bubbles up and down in your glass;
6. If you want to continue to observe the effect just add another teaspoon of salt to the oil.

What happened?

Of course inside the glass we don’t have thru lava, the true is less fantastic, it looks like lava but its like those cheep lava lamps used in 1960’s.
First, the oil floats on water because it is lighter than water.
Then the salt is heavier than oil and sinks in water. When this happens the salt takes a bit of oil with it when goes down and the bubble is formed, when salt dissolves ... bang! Oil goes back up to the surface of the water.

If your young restless mind want to take the step further try to answer these questions:

1. How long will the effect stands if you continue to add salt?
2. Changing the type of oil produces different results? and olive oil?
3. In addition to salt, is there any substance that works?
4. Does the height or shape of the glass affects the results?

Et Voila!

Enjoy!