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Science progress affects our daily life and "to know" means you are going to chose right, because it allows you to form your own opinion on scientific everyday issues. On the other hand, having an elegant and harmonious vision of the world where we live in leads to a feeling of intellectual satisfaction.
We believe this kind of scientific day to day knowledge should be encouraged from an early age, and that's why this project was born: science, culture, knowledge, crafts for your restless mind.

Saturday, May 4, 2013

Emulsion, oil/ water coloring droplets

Cleaning the fryer back home is not exactly easy. Who usually does this knows that is a messy, sticky and dirty work. To minimize this greasy effect we usually fill the fryer with boiling water and add detergent on a very generous amount. In fact I usually pre wash all the dishes before putting them in the machine. Why? Because it allows the fat to dissolve in the water and not inside the machine or in my hands.

Because the detergent is an emulsifier, and as such promotes the formation of emulsions.
An emulsion is a system consisting of two immiscible liquid phases (oil and water). We may have emulsions of oil in water (O / W: external aqueous phase) and water in oil (W / O: oily external phase).
The emulsion stability is ensured with use of emulsifying agents such as detergent, surface-active substances generally.

We will need:
  • 3 transparent cups, glass or plastic,
  • water, enough to fill two cups,
  • cooking oil,
  • food coloring,
  • pencils.
How to:
  1. Fill one of the containers with water (2/3) and the other with the same amount of cooking oil;
  2. Add 3-5 drops of food coloring to each, leave some space between the drops so that they do not touch each other;
  3. What happens?
  4. Fill the third container with water up to 2/3, add some oil, enough to form a layer on top of the water.
  5. Add the food coloring the same way as in the previous point. Try to predict what will happen;
  6. What happens?
  7. With the sharp pencil touch a droplet of colorant of the third cup;
What happens?
When the food coloring is added to water, it blends completely with it. When you add the same food coloring to the oil, a small sphere is formed on oil surface.

Water molecules are polar, in other words they have a small positive charge at one end and a small negative charge at the other, for this reason they remain together, by forming hydrogen bridges. Unlike water molecules, the oil molecules are non-polar - have no charge-, for this reason, the molecules of oil also tend to stick together.

When we "force" an oil to mix with a water based solution (the food coloring) those form an emulsion.

A emulsifier it's a molecule with to different ends, one that loves water (hydrophilic) and a second that hates water (hydrophobic). Imagine a wood stick with two ends, one of them "sinks" in the oil- the hydrophobic end- the other in the water- hydrophilic end. This phenomena is responsible for the formation of small oil droplets -spheres- in the water. This is a stable structure and it's what we call emulsion, many things around us at home are emulsions like mayonnaise and face creams, for example.
If you try to mix the jar 3 emulsion you will verify that after a while the oil will came back to the top..

When you use food coloring (FC), what happens is that the FC droplets drag a small amount of oil with them as a "coat", that's why the FC stop in the oil. the oil acts as a life saver coat, preventing the droplets to drawn. When you punch the droplets with the sharp pencil, the "oil coat" is broken and the FC- a water based solution- blends, almost immediately, with the water bellow the oil. 

Go further
If you want to go further change the variables, one at time and take notes.
  • Use different kitchen oil types;
  • Use vinegar or any other kitchen liquid instead of FC.

Et voilá!
Now you can avoid your daily bath: "Mom I'm hydrophobic!"


The air takes space- water in the jar

This is a very simple demonstration that proves the air takes space

We will need:
  • 2 jars,
  • funnel,demonstração, experiência de física, pressão, propriedades do ar, água,
  • water,
  • modeling clay, a lot,
  • coloring, food coloring is the best,
  • pencil, or a pen, a wood stick, something good to punch the clay ...
How to:
  1. Fill half of the jar with water;
  2. Add a few food coloring to the water, 3 or 4 drops;
  3. Place the funnel in the jar;
  4. Seal the jar area around the funnel with the modeling clay, the air can't go in or out through the jar/funnel contact zone;
  5. Now fill the funnel with some more water.

What happens?
A small quantity of water rolls through the funnel into the flask, but in a few seconds stops, despite the funnel is full of water.

There is no more space in the jar! The jar is half full of water and half full of air, we must to take the air out in order to get the water get in.

Use the pencil to open a hole in the clay.

What happens?
The water immediately falls into the jar.

The water "falls" and pushes the air out the jar, now the air can get out through the hole.

Et voilá!
Easy uh?


Growing crystals at home

What is a crystal?
Crystals are regular structures formed by a regular repeating pattern of atoms or molecules.

These structures grow by a process called nucleation. During nucleation, the atoms or molecules of what we want to transform in a crystal (solute) are dissolved in a solvent. The particles of the solute will tend to cluster together, forming subunits of atoms or molecules. These larger particles will also group with each other and eventually become large enough to "pop out" the solution (crystallize).

Other solute molecules will continue to adhere to the surface of the crystal, causing it to grow until equilibrium is achieved between the solute molecules in the crystal and the solution.

Growing crystals
Three factors that can influence the growth of "home" crystals:
  • A good/poor solution saturation- The first stage of home crystal growth is a saturated solute. In a saturated solution the probability of molecules colliding with each other in order to form a core for initiating nucleation is greatly increased.
  • Surface type-A rough surface tends to be more attractive for nucleation. It is more likely that a crystal is formed on a piece of rough rope than the in the smooth walls of a glass.
  • The presence of deposits in the bottom-This occurs when the solution is not scrambled or means that too much solute was added to saturate the solution. The presence of these deposits create areas for optimum crystal growth however prevents crystal formation in the "target."
Lets see how to grow sugar crystals, these crystals can be sucked and eaten like a lollipop. This demonstration may take up to 3 weeks.

We will need:
  • 3 cups of sugar, we have to adjust this quantity, we want to saturated at 100% but no precipitate,
  • cup of water, to boil,
  • food coloring,
  • small jar,
  • small bowl,
  • wood stick, or rope,
  • kitchen paper or paper filter.
How to:
  1. Boil the water, careful with burns!;
  2. In the bowl, mix the boiling water with the sugar;
  3. Stir the water until all the sugar is dissolved;
  4. If you want to give sugar some color, now it's the time, add the food coloring;
  5. Place this solution in the jar, attention! wash the jar really well to avoid nucleation in it's walls;
  6. Avoid any amount of sugar precipitate in the jar- any not dissolved sugar-, this sugar will be a good nucleation "start point";
  7. Suspend the stick or rope in the solution, do not wash those, we want this to be a suitable "start up" spot for nucleation;
  8. Chose a nice and quiet spot to place your jar for at least 3 weeks;
  9. Wait until the solution cool and cover it with a paper filter. 
What happens?  
After cooling the solution will use nucleation spots to form crystals.

NOTE: You must check the jar on daily basis, if you see any nucleation in jar walls, change the jar;

Wait about 3 weeks for excellent results.

Go further:
  • Follow the growing crystals with a graph;
  • Use salt and compare the growing velocity with the sugar;
  • Use 3 jars, in the first one use boiling water, in the second tepid water, and in the last one repeat the essay with cold water;
  • Try to dissolve the sugar/salt/other while the water is boiling;
  • I am sure you can remember other ways to change this demonstration into a experiment...
Et Voilá!
Science you can eat!  

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