Сборник текстов на казахском, русском, английском языках для формирования навыков по видам речевой деятельности обучающихся уровней среднего образования
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- Бұл бет үшін навигация:
- Conductivity
- Chemical Reactions Neutralization Acids will react with bases to form a salt and water. This is a neutralization
- Earth Chemistry
- Chemistry of Carbon and Its Compounds
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Bromothymol blue is an indicator that turns blue in a base, or yellow in acid. Made with special chemical compounds that react slightly with an acid or base, indicators will change color in the presence of an acid or base. A common indicator is litmus paper. Litmus paper turns red in acidic conditions and blue in basic conditions. Phenolphthalein purple is colorless in acidic and neutral solutions, but it turns purple once the solution becomes basic. It is useful when attempting to neutralize an acidic solution; once the indicator turns purple, enough base has been added. Conductivity A less informative method is to test for conductivity. Acids and bases in aqueous solutions will conduct electricity because they contain dissolved ions. Therefore, acids and bases are electrolytes. Strong acids and bases will be strong electrolytes. Weak acids and bases will be weak electrolytes. This affects the amount of conductivity. However, acids will react with metal, so testing conductivity may not be plausible. Physical properties The physical properties of acids and bases are opposites.
These properties are very general; they may not be true for every single acid or base.
Another warning: if an acid or base is spilled, it must be cleaned up immediately and properly (according to the procedures of the lab you are working in). If, for example, sodium hydroxide is spilled, the water will begin to evaporate. Sodium hydroxide does not evaporate, so the concentration of the base steadily increases until it becomes damaging to its surrounding surfaces. Chemical Reactions Neutralization Acids will react with bases to form a salt and water. This is a neutralization 483 reaction. The products of a neutralization reaction are much less acidic or basic than the reactants were. For example, sodium hydroxide (a base) is added to hydrochloric acid. This is a double replacement reaction.
produce a metal salt and hydrogen gas bubbles.
carbonates to produce water, CO2 gas bubbles, and a salt. Acids react with metal oxides to produce water and a salt. Bases Bases are typically less reactive and violent than acids. They do still undergo many chemical reactions, especially with organic compounds. A common reactions is saponificiation: the reaction of a base with fat or oil to create soap. Earth Chemistry The chemical term earths was historically applied to certain chemical substances, once thought to be elements, and this name was borrowed from one of the four classical elements of Plato. "Earths" later turned out to be chemical compounds, albeit difficult to concentrate, such as rare earths and alkaline earths. Earths are metallic oxides, and the corresponding metals were classified into the corresponding groups: rare earth metals and alkaline earth metals Let’s take a moment for a closer look at the Earth’s chemistry; in particular, the chemical elements interspersed in the Earth’s major depths. With an atmosphere containing 78% nitrogen and 21% oxygen, the Earth is the only planet in the solar system capable of initiating and sustaining life-forms; the various chemical elements that make up the Earth, from the crust, down to the mantle and core, have a little something to do with that. Defining the Earth’s Boundaries and Elements As scientists are not able to visit the Earth’s deep interior or place instruments within it, they explore in subtle ways. One approach is to study the Earth with non-material probes, such as seismic waves emitted by earthquakes. As seismic waves pass through the Earth, they undergo sudden changes in direction and velocity at certain depths. These depths mark the major boundaries, also called discontinuities, that divide the Earth into crust, mantle and core. The Crust. The Earth’s crust is the thin outermost layer of the Earth, with an average depth of 24 km (15 mi). The crust accounts for 1.05% of the Earth’s volume and 0.5% of its mass. The chemical elements oxygen, silicon and aluminum dominate the crustal composition. The major mineral type – the feldspars – are alumino-silicates of the alkali and alkaline-earth metals. Silicon dioxide is the second most
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common group. The Mantle. The mantle extends from the base of the crust to the core and is about 2865 km (1780 mi) thick, occupying about 82.5% of the Earth’s volume. The upper mantle is rich in olivine and pyroxenes. The major mineral type in the lower mantle appears to be pyroxenes, especially magnesium silicate. Scientists think that the lowest layer of the mantle called “D layer” is richer in aluminum and calcium than the higher layers of the mantle. The Core. The core extends from the base of the mantle to the Earth’s center, and is 6964 kn (4327 mi) in diameter – accounting for only 16.3% of the Earth’s volume, but 33.5% of its mass. The core is made up of two distinct parts – a liquid outer core, which is 2260 km (1404 mi) thick, and a solid inner core, which has a radius of 1222 km (759 mi). The core is chemically distinct from the mantle and contains about 89% iron and 6% nickel. The remaining 5% is made of lighter elements, possibly sulfur – but we cannot rule out the presence of oxygen and silicon, in light of a 2013 study published in Nature, which calls them “prime candidates” for the lighter elements in the Earth’s core. Earth Chemistry As we celebrate Earth Day, and as in recent times, emphasis has been given to environmental awareness or the value of “green.” This year, let’s pay attention to all the other colors of Earth as well – the colors we see through chemistry. Chemistry of Carbon and Its Compounds PrevNextchapter List Carbon: Introduction Atomic Number: 6
Valence electrons: 4 Property: Non-metal Abundance: Carbon is the 4th most abundant substance in universe and 15th most abundant substance in the earth’s crust. Compounds having carbon atoms among the components are known as carbon compounds. Previously, carbon compounds could only be obtained from a living source; hence they are also known as organic compounds. Bonding In Carbon: Covalent Bond Bond formed by sharing of electrons is called covalent bond. Two of more atoms share electrons to make their configuration stable. In this type of bond, all the atoms have similar rights over shared electrons. Compounds which are formed because of covalent bond are called COVALNET COMPOUNDS. Covalent bonds are of three types: Single, double and triple covalent bond. Single Covalent Bond: Single covalent bond is formed because of sharing of two electrons, one from each of the two atoms. Formation of hydrogen molecule (H2)
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Atomic Number of H = 1 Electronic configuration of H = 1 Valence electron of H = 1 Hydrogen forms a duet, to obtain stable configuration. This configuration is similar to helium (a noble gas). Since, hydrogen has one electron in its valence shell, so it requires one more electron to form a duet. So, in the formation of hydrogen molecule; one electron from each of the hydrogen atoms is shared. 
Formation of hydrogen chloride (HCl): Valence electron of hydrogen = 1 Atomic number of chlorine = 17 Electronic configuration of chlorine: 2, 8, 7 Electrons in outermost orbit = 7 Valence electron = 7 
Formation of chlorine molecule (Cl2): Valence electron of chlorine = 7 
Formation of water (H2O) Valence electron of hydrogen = 1 Atomic number of oxygen = 8 Electronic configuration of oxygen = 2, 6 Valence electron = 6 
Oxygen in water molecule completes stable configuration by the sharing one electron from each of the two hydrogen atoms. Formation of Methane (CH4)
Valence electron of hydrogen = 1 486
Formation of Ethane (C2H6): 
Double covalent bond: Double bond is formed by sharing of four electrons, two from each of the two atoms. Formation of oxygen molecule (O2): Valence electron of oxygen = 2 
In the formation of oxygen molecule, two electrons are shared by each of the two oxygen atoms to complete their stable configuration. In oxygen, the total number of shared electrons is four, two from each of the oxygen atoms. So a double covalent bond is formed. Formation of Carbon dioxide (CO2): Valence electron of carbon = 4 Valence electron of oxygen = 6 
In carbon dioxide two double covalent bonds are formed. Formation of Ethylene (C2H4): Valence electron of carbon = 4 Valence electron of hydrogen = 1 
Triple Covalent Bond: Triple covalent bond is formed because of the sharing of six electrons, three from each of the two atoms. Formation of Nitrogen (N2): Atomic number of nitrogen = 7 Electronic configuration of nitrogen = 2, 5 Valence electron = 5 487 
In the formation of nitrogen, three electrons are shared by each of the nitrogen atoms. Thus one triple bond is formed because of the sharing of total six electrons. Formation of Acetylene (C2H2): 
Properties of Covalent Bond: Intermolecular force is smaller. Covalent bonds are weaker than ionic bond. As a result, covalent compounds have low melting and boiling points. Covalent compounds are poor conductor of electricity as no charged particles are formed in covalent bond. Since, carbon compounds are formed by the formation of covalent bond, so carbon compounds generally have low melting and boiling points and are poor conductor of electricity. 5.1 Biochemistry, sometimes called biological chemistry, is the study of chemical processes within and relating to living organisms.[1]By controlling information flow through biochemical signaling and the flow of chemical energy through metabolism, biochemical processes give rise to the complexity of life. Over the last decades of the 20th century, biochemistry has become so successful at explaining living processes that now almost all areas of the life sciences from botany to medicine to genetics are engaged in biochemical research.[2] Today, the main focus of pure biochemistry is on understanding how biological molecules give rise to the processes that occur within living cells,[3] which in turn relates greatly to the study and understanding of tissues, organs, and whole organisms[4]—that is, all of biology. Biochemistry is closely related to molecular biology, the study of the molecular mechanisms by which genetic information encoded inDNA is able to result in the processes of life.[5] Depending on the exact definition of the terms used, molecular biology can be thought of as a branch of biochemistry, or biochemistry as a tool with which to investigate and study molecular biology. Much of biochemistry deals with the structures, functions and interactions of biological macromolecules, such as proteins, nucleic acids, carbohydrates and lipids, which provide the structure of cells and perform many of the functions associated with life.[6] The chemistry of the cell also depends on the reactions of smaller molecules and ions. These can be inorganic, for example water andmetal ions, or organic, for example the amino acids, which are used to synthesize proteins.[7] The mechanisms by which cells harness energy from their environment via chemical 488
reactions are known as metabolism. The findings of biochemistry are applied primarily in medicine, nutrition, and agriculture. In medicine, biochemists investigate the causes and cures of diseases.[8] In nutrition, they study how to maintain health and study the effects of nutritional deficiencies.[9] In agriculture, biochemists investigate soil andfertilizers, and try to discover ways to improve crop cultivation, crop storage and pest control. Biochemistry is the branch of science that explores the chemical processes within and related to living organisms. It is a laboratory based science that brings together biology and chemistry. By using chemical knowledge and techniques, biochemists can understand and solve biological problems. 
Biochemistry focuses on processes happening at a molecular level. It focuses on what’s happening inside our cells, studying components like proteins, lipids and organelles. It also looks at how cells communicate with each other, for example during growth or fighting illness. Biochemists need to understand how the structure of a molecule relates to its function, allowing them to predict how molecules will interact. Biochemistry covers a range of scientific disciplines, including genetics, microbiology, forensics, plant science and medicine. Because of its breadth, biochemistry is very important and advances in this field of science over the past 100 years have been staggering. It’s a very exciting time to be part of this fascinating area of study.
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