Monday, 19 January 2015



Characterizes the plants is the ability to manufacture the food itself, with a process called photosynthesis. This process takes place in all green parts of a plant, especially in leaves, thanks to the presence of chlorophyll in the chloroplasts of plant cells.

Chlorophyll is a green substance capable of absorbing the light of the sun and of containing the energy. By means of this energy, a chemical reaction occurs in the chloroplast between the water absorbed by the roots in the soil, and the carbon dioxide present in the air.

First, the water is decomposed into its two components, hydrogen and oxygen, then the hydrogen combines with the carbon dioxide forming a particular sugar: glucose. This sugar is the food that will feed the plant, while the oxygen will be emitted into the air.

Photosynthesis takes place when the crude sap (water and minerals) rises through the lymph channels up to the leaves, real laboratories of the plant, where under the action of chlorophyll (particular substance that gives plants the green color) and with the energy of sunlight, carbon dioxide and minerals are transformed into elaborated sap (sugars and oxygen).

The oxygen through the stomata is released into the environment, while the sugars are retained by the plant which uses them to live, to grow, build leaves, flowers, fruits and seeds.

Photosynthesis occurs in day in the presence of sunlight, while at night the oxygen and sugars are retained by the plant and the carbon dioxide is emitted into the environment. 

The Value Of Chemistry In Everyday Life


In everyday life we encounter on a daily basis with the products of the chemical industry. Now household chemicals - is an independent industry. Every year the world produces about 30 million. Tons of household chemicals. This detergents, disinfectants, care for furniture and flooring, to control insects and plant protection agents for whitening, starch, various paints, glues, cosmetic, etc ..

In everyday life, widely adopted detergents. They belong to the surfactants and successfully remove dirt from the surface of tissues. Depending on the purpose of the synthetic detergents include various alkaline additives: sodium silicate, sodium phosphates, sodium carbonate, which facilitate washing cotton and linen fabrics, nylon. But these detergents cannot be used for washing wool and Dacron, since they are gradually destroyed by an alkaline medium. For such products used detergents that create a water neutral.

Some detergents contain bleach destroying dirt resistant, due to which the tissue acquires a gray or yellow. Bleach Sodium perforate can be NaBO3 • 4H2O Na2O2 sodium peroxide and hydrogen peroxide H2O2.

To clean the dishes, bowls in detergents often introduced solid inert substance - abrasives that facilitate mechanical destruction of solid contaminants.

Chemistry produces a wide range of personal care products, perfumes and cosmetics, insecticides, bucks and much more.

The Surface Tension


In the field to the liquid state each molecule is surrounded by other molecules: the attractive forces between molecules, for the fact that each of them is completely surrounded by other, are balanced allowing each molecule moves freely (there is no prevalence of forces in some direction).

Just below the surface of the liquid, we can consider a layer as thick as the diameter of the molecules forming the liquid: this layer is called the boundary layer and is that on which the transition from liquid to gas, a solid or another liquid. A molecule that is located in this area has other molecules of the same type above it. If a molecule that is located Nallo boundary layer is raised, the links between it and the adjacent molecules are stretched, creating a force which tends to draw the molecule to the surface. Similarly, by placing a tiny body on the surface of a liquid, the surface molecules latter is pushed downwards by generating a return force directed upwards.

The surface of a liquid then behaves like a stretched membrane.

The surface tension of a liquid is effort that must be done to bring a ample number of molecules from the inside of the liquid to the surface to form a new unit area of said surface. This work numerically coincides with the contraction force exerted on a hypothetical line laid on the surface.
It defines the coefficient of surface tension measured in N / m or J / m2

The surface tension is measured directly by measuring the force required to break the surface of the liquid raising a thin wire from the surface itself.
Needle up from the surface

It is found that this force is directly proportional to twice the length of the wire (which isi explains what thinking that there is the surface of liquid on both sides of the wire).
The force required to pull a thread mass m and length L is:

F = 2 tau L + m g

Study Visa For U.S.A


Most non-US citizens wish to study in the U.S.A will seek an F-1 student visa (non-immigrant), but there are other types of visas that are sometimes allowed for those studying in the United States. A brief description of different types of study visas.

F-1 Student Visa

This type of visa is most common for peoples who wish to engage in academic studies in the United States of America. This is a Visa for those who wish to study at an accredited US College or a University or who wish to study at a university or language institute Intensive English.

Redemption policy of SCEL

Information about obtaining a refund if you cancel your application or if your visa is denied.

Redemption policy of SCEL.

Types of Visa


In general terms, we can distinguish visas into two broad categories, determined by the duration of visa:

Short-term visas, provided for stays up to 90 days over the period of 180 days, calculated from date of the 1st entry into the Schengen area.

Schengen visas are uniform (VSU) and visas to territoriality Limited (VTL). Uniform visa is valid for the entire territory of the Schengen States; visas to territoriality Limited, issued only in exceptional cases, are valid for the country of one or more Member States but not for everyone;

The national visas allow entry for long stay only in the State that issued and circulated, also waiting for the residence permit, within the Schengen area up to a maximum of 90 days.
The uniform Schengen visa is a visa type C, the national visa is a visa type D.

Visas for short stay may be issued for the purpose of: business, medical care, sports competitions, invitation, self-employment, employment, mission, religious reasons, study, transport and tourism.
Visas for long stay may be issued to: adoption, medical care, diplomatic reasons, family member, self-employment, employment, mission, religious reasons, re-entry, choice of residence, family members, students, working holidays.

Newton's Laws of Motion


First law: the principle of inertia:

The first law of Newton states that the principle of inertia that an object retains its speed and direction of motion unless a force is applied to it. This principle may seem surprising: it is generally assumed that if no there is no force on a object then it must be at rest, that is to say still. The principle of inertia states that this is not the case!

It is difficult to verify this principle on Earth because the objects are usually subjected to forces. Slippery ice skater approaches this situation. If a bicycle is stopped after a few tens of meters when not pedal, it is because tire friction forces on the road and the bike with air. In space, there is no air is no friction. If an astronaut drops a object it away in a straight line at constant speed, never stopping, according to the principle of inertia, unless attracted by gravity or meet an obstacle.

Second Law: Fundamental principle of dynamics:

The second law has different names, but most often it is called the fundamental principle of dynamics. It's a tie between vectors, which states that, the acceleration of an object, {vec. a}, is proportional to the sum of the forces {vec F} _ {k} he suffers and inversely proportional to its mass.

m { vec a} =  sum _ {k} { vec F} _ {k}

This means for example that if we drop an object on Earth, its movement will be accelerated because of his weight. It will therefore fall faster and faster.

The acceleration vector {vec a} is the same direction as the vector sum of the forces {vec F} _ {k} applied to the object. So for an object to be at equilibrium (constant speed) requires that the sum of the force vectors is the zero vector:

{vec = {a} frac 1m}  sum _ {k} {vec F} _ {k} = {vec 0}

We can consider that the first law of Newton is a special case of the second: if no there is no force on an object then its acceleration is zero which means that its speed is constant.

Third law: the principle of reciprocal actions:

The third law is the principle of reciprocal actions. It states that if a body exerts a force on one another, while the opposite is true. In other words, if an object A exerts a force on object B, then B also exerts a force on A in the same direction and with the same intensity but in the opposite direction (toward A).

This is the principle of jet propulsion.

For example.

A rocket ejects gas by its reactor nozzles. It exerts a force on these gases to eject. In response, the gases exert a force on the rocket: it is this force that off the ground and propelled into space.