Water properties- Adhesion and Cohesion

If we talk about water we must refer cohesion and adhesion.
We already talk about another water properties the surface tension, but without the first two the triad wouldn’t be complete.
Most of the times water molecules are attracted to each other, in this case we are dealing with cohesion, on the other hand, if water molecules are attracted to other materials then we are dealing with adhesion.


What makes it possible?
As we said in other articles water molecules are made by 2 H atoms and one O atom, this gives water molecule a neutral charge, but its structure allows the water molecule to establish hydrogen bonds between H atoms from different molecules, this bonds make molecules closer from each other, that phenomenon is called cohesion. If the attraction between the H atoms is weaker then the attraction between water molecules and other material molecules surrounding, the water molecules will bond to this surrounding material instead, we call this adhesion.


Examples:
All hydrophobic surfaces will repels water, this means the water molecules are not attracted to it and they form drops, this is cohesion, like wax paper or any waxed surface. Like the shower after being cleaned with specific soap, in fact a thin hydrophobic layer is formed to repel water- Cohesion.
It is also due to cohesion that the rain falls in droplets rather than molecules, otherwise we would call rain to something completely different


When water molecules are attracted to other surrounding molecules the phenomenon is called adhesion. We saw it here, remember? The water "climbed" the paper against gravity, this happened because water molecules were strongly attracted by cellulose molecules on the paper, this attraction was stronger then the attraction between H2O molecules.


Note this phenomenon only occur because one of the forces is stronger then the other.


In short:
Cohesion- when attraction forces between water molecules are stronger then the attraction forces between water and surrounding material molecules.
Adhesion- when attraction forces between water molecules are weaker then the attraction forces between water and surrounding material molecules.


The following demonstration its very simple and works very well to show cohesion


What we need:

1. 2 styrofoam cups,
2. water,
3. sharp pencil or any sharp object like a nail,
4. a bowl.

How to:

1. Choose an appropriate location;
2. With the pencil make two holes in the first cup, as close as possible but not touching, don't make them too large;
3. Fill the second cup with water;
4. Hold the punched cup above the bowl;
5. Pour the water from the second cup into the first;
6. The water should start to fall through the holes you made with the pencil;
7. Quickly, "hold" the two "threads" of water with your fingers (thumb and index).

Results:
The 2 "threads" become one.


Why?
The water molecules are attracted to each other.


Please note:

• Probably you will not make it work at first time, try again.
• If you are lucky you will achieve the optimal distance between the holes, in that scenario you will not need to use your fingers, the "threads" will become one naturally.

Sources: http://www.uni.edu/~iowawet/H2OProperties.html; http://www.physlink.com/education/askexperts/ae543.cfm

Et voilá!
Don’t get wet!
Enjoy!

Art with beach stones

Your restless can role play with this. Make a masterpiece with beach stones.
This is another summer craft you can do all year, is always fun and they love it.
Buy an art board, or make yourself one with a piece of wood, and invite your restless to make art with stones, the result always work.

What we need:

• beach stones, several formats and colors,
• art board,
• white glue
• charcoal,
• beach sand, optional
• acrylic paint, optional,
• varnish, optional,
• brush, optional.

How to:

1. Wash all the stones, first with water and after with alcohol;
2. Separate the stones by color, size and format;
3. With a charcoal, draw, with light strokes, the design you wish to replicate with the stones, for some restless the "we will see as we go" works best;
4. Geometric designs always work in this project, triangles, circles, straight lines...
5. Apply white glue on the art board;
6. One by one, glue the stones to the board as you with, to form the design you want. Use colors, formats and sizes to do the pattern;
7. After you finish spread the sand on it, the sand will glue to the "empty spaces";
8. Let it dry for 24h;
9. You can paint stones outlines with acrylic paint if you wish, let it dry for 4;
10. Before varnish remove the sand.

Et Voilá!
Hang your master piece on the wall, and wait for next summer.

Enjoy!

How to do Slime

Homemade slime is very easy to do and give us hours of fun.

What we need:

• white glue,
• 2 plastic cups, trash it when you finish it,
• food coloring (green is the classic but you can make red or blue slime, chose your favorite color),
• water,
• borax (you can find it in drugstore),  
• plastic tablespoon,
• regular tablespoon.

How to:

1. Fill 1 cup with water;
2. Add a Borax tablespoon, use the plastic spoon and mix well,
3. Reserve this solution,
4. On the other cup measure about 1in of white glue,
5. Add 20ml of water (that's about 3 tablespoons),
6. Mix,
7. Add 4 drops of food coloring,
8. Add to the second cup 1 tablespoon of Borax solution,
9. Mix,
10. Wait 30seg,
11. Play with it.

NOTE THIS:

• Slime is totally safe for the skin.
• Keep the slime closed in a jar when you are not playing with it.
• Don't use it near your hair or carpets and rugs.
• Keep it away from the younger children and pets.
• Don't eat it.

Results:

The polymer formed is both a solid and a liquid. This polymer can behave like a liquid and take the shape of the glass, and yet, you can hold it in your hand like a solid. Substances like this one are called non-Newtonian fluids... and what is this? Exactly what we wrote before, or in scientific speech is a fluid whose viscosity is variable depending on the applied pressure.

You can make this demonstration an experience
Answer with your restless to the following questions:

• How does the Slime change with the Borax quantity in the first solution?
• How does the Slime change with the Glue quantity in the second solution?  
• What is the best way to store your slime? Try several yes of boxes, jars, bottles..
• Does the Borax trademark make a difference? Witch one works best?
• What about the glue?
• What is the ideal water quantity? Try to do several slimes with different water quantities.

NOTE THIS:
Never change 2 or more variables at the same time. For instance, if you change the water quantity keep the glue trademark the same.

Et Voilá!
You want fun? Play with non-Newtonian fluids

Enjoy!

Beach shell frames- Summer DIY

You can find a few summer activities here, but this one is really a summer activity.

The idea is to make some frames for our pictures using materials we find on a summer walk along the beach. I don’t know about you but every time I come home from the beach we bring tons of stones and shells...

This tutorial will help all restless to use their stone/shells collection to do something that will remind them, when the winter comes, the hot and nice days of summer.

What we need:

• a photograph,
• tape,
• white glue,
• shells,
• exact-O knife or scissors,
• Pencil or pen,
• ruler,
• cardboard can be a piece of a cardboard box,
• Thick cardboard,
• Acrylic paint, optional,
• Sand from the beach, optional,
• Varnish, optional.

How to:

1. First of all chose the photo you want to frame;
2. Make 2 little rolls with the tape and fix it to the cardboard;
3. Outline the picture with the pencil;
4. With the ruler and the pencil draw the frame format, if you can't make it symmetric draw it clearly asymmetric, otherwise will look weird;
5. Take the photo off;
6. Again, with the ruler and pencils help, draw a second outline 1/2in around the original photo outline, like the photo is 1/2 smaller;
7. With the exact-O knife cut the frame;
8. Place the frame on the tick cardboard;
9. Draw the frame exterior outline on the cardboard;
10. With the exact-O knife cut the second cardboard, remember to cut "inside" the pencil stroke, otherwise the back cardboard will be bigger then the front frame;
11. Spread white glue on the frame, not too much or the shells will drown in glue;
12. Place the shells like your imagination/creativity tells you to, you don’t need to fill up all empty spaces;
13. If you want to use sand, now its the time, cover all the frame with it;
14. Wait for 24h;
15. If you wish to use acrylic painting:
1. First option is to dye the glue, before apply the glue mix paint on it as you wish;
2. Second option is to paint shells after the glue, wait 24h before apply the paint.
16. Remove the excess of sand;
17. Glue the photo in the frame back;
18. Let it dry for 2h;
19. Glue the cardboard in the back, to protect the photo;
20. Varnish it if you want.

Et Voilá!
Summer in a shot!

Enjoy!

Instant facts- Just add water 9

The Cookie Monster from Sesame Street was originally named Sid.
in http://www.ireallylikefood.com/725307903/7-facts-about-cookies/

Tangram- some cool videos about this math puzzle

Today, on invited restless mind, we have some videos for you about Tangram:

And to finish, my favourite:

Et voilá!
7 dancing "tans" to make nice images, can you do it?

Enjoy!

Instant facts- Just add water 8

Chinese Sturgeon its a carnivore fish with a life span in the wild of 50 to 60 years.

in http://environment.nationalgeographic.com