A third blood group system was discovered from experiments developed by Landsteiner and Wiener in 1940 with monkey blood of the genus Rhesus. These researchers found that by injecting the blood of this monkey into guinea pigs, antibodies were produced to combat the introduced red blood cells.
A study conducted in the United States compared the reaction of rats to ingestion of Oreo crackers and drugs such as cocaine and morphine. The wafer was used in the study to test the effect of high calorie foods with high sugar concentration. Neuroscience professor Joseph Schroeder and some of his students have found that eating Oreo, one of the most famous stuffed crackers in the United States, can activate more neurons in the pleasure-associated brain region than taking drugs.
For experts, addiction gives the same pleasure as alcohol and drugs. Technology addiction is 'cousin' to disorders like kleptomania and pyromania. A study by Yahoo consulting firm Flurry found that there are 280 million mobile app "addicts" in the world, but it has no medical base.
Life in big cities makes people more prone to mental illness and anxiety. The group that walked in the park was much calmer and with less activity in the prefrontal cortex. Several studies indicate that people who live in the centers of large cities are more prone to anxiety and mental illness than those who live closer to nature.
All chemicals are formed by atoms of chemical elements. Scientists have observed that the vast majority of known substances consist of combined atoms together. Sometimes they are atoms of the same element, sometimes of different elements. Of the millions of known substances, only six are known to contain unmatched atoms.
Rutherford's atomic model was complemented by a new concept introduced by Danish physicist Niels Bohr: “The electron describes a circular orbit around the nucleus without gaining or losing energy.” Each orbit described by the electron is called the energy level or energy layer. .
As we saw earlier, Bohr refined Rutherford's atomic model based on theoretical formulations. One is this: Electrons are distributed according to their distances from the nucleus, describing circular orbits around the nucleus without gaining or losing energy. Thus, there are several circular orbits in an atom, and each one has a certain energy value.
Homogeneous mixtures are also called solutions. The components (substances present) of a solution may be in the states: solid, liquid or gaseous. We can say that the solution is a type of matter formed by a solvent and a solute. Solute is the substance that is dissolved in the solvent.
Decantation: Used to separate components from heterogeneous mixtures consisting of one solid and one liquid component or two liquid components, these liquids must be immiscible. This method consists of letting the mixture stand and the denser component, under the force of gravity, will form the lower phase and the less dense will occupy the upper phase.
The water molecule is made up of two hydrogen atoms and one oxygen. Already the nitrogen gas, which exists in the atmosphere, is formed by the union of two nitrogen atoms. The same goes for oxygen gas. We then say that oxygen is a simple substance, since it is formed by the union of chemically equal atoms.
We differentiate a mixture of a pure substance normally by its physical constants, such as: boiling point (PE), melting point (PF), density (d) and solubility (solub). Pure substances maintain their constants during changes. different from mixtures. Example: Pure water: - PE = 100 ° C; Mp = 0 ° C; d = 1g / cm 3.
This law was drafted in 1774 by the French chemist Antoine Laurent Lavoisier. Lavoisier's experimental studies led him to conclude that in a chemical reaction, which takes place in a closed system, the sum of the reactant masses is equal to the sum of the product masses: m (reactants) = m (products) For example, when 2 grams of hydrogen react with 16 grams of oxygen, 18 grams of water is formed. When 12 grams of carbon react with 32 grams of oxygen, 44 grams of carbon dioxide is formed.
Temperature range and thermal sensations In our daily lives, we are accustomed to having hot or cold sensations when we touch some objects. They are thermal sensations. We are used to associating these thermal sensations with the concept of temperature. We say, for example, that the temperature of an ice stone is lower than that of a roast beef that has just been removed from the oven.
Consider two iron cubes, one at 10 ° C and one at 30 ° C, that are not in direct contact, because between them was placed a layer of another material. If because of this, the thermal equilibrium is retarded, we say that this material is a thermal insulator. There is no perfectly insulating material that completely prevents heat exchange, but there are materials that, in practice, greatly slow the heat exchange.
A third mode of heat transfer from a warmer to a colder body is thermal radiation. Unlike the other two processes, conduction and convection, irradiation allows heat transfer, or radiant heat. Heat waves from the sun travel a great distance in a vacuum until they reach Earth and transfer heat to it from the sun.
Resulting force produces acceleration If a body is at rest (relative to a certain frame), its velocity is zero. If it is set in motion, its speed will no longer be zero and therefore the object has been accelerated. Similarly, if a body in straight and uniform motion (and thus with zero acceleration, since the velocity is constant) is forced to stop, we can also say that it has accelerated (popularly in this case "slowdown").
Imagine the following situation: you need to lift a bag full of groceries. The total mass of the bag is 120 kg. Few people can, and usually only those who prepare for it. However, throughout history, people have often had to lift stones or objects, and have no machines to assist them.
One or more substances, present in the initial state of a system, become one or more different substances, which will be present in the final state, the transformation is a chemical reaction, or chemical transformation. In other words, chemical reaction is a process in which new substances are formed from others.
Have you observed in person, in sports programs or in movies, that in fitness centers, weight machines are full of hard disks around which there is a cord, on which loads are attached? What are worth for? These discs are called pulleys or pulleys. They are discs with a channel through which a wire or rope passes, in which a load is attached.