Huwerl Thornton, Jr.
All matter on earth is made up of a mixture of about 100 pure substances which are called the elements.
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Atoms are the smallest particle into which an element can be subdivided without losing its characteristic properties.
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The ancient Greeks gave us the idea and the word atoms. To them it meant fundamentally and invisibly small particles of matter. The ancient Greeks also believed that an atom was "uncuttable" or "indivisible".
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Atoms are extremely small. So small in fact that about 100 trillion would fit into the period at the end of this sentence.
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The subatomic particles of an atom are called electrons, protons, and neutrons. The different properties of the elements arise from the varying combinations of subatomic particles that make up their atoms.
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When two or more atoms bond together, they do so by sharing electrons with one another. When atoms bond, they form a molecule. The molecule relates to a chemical compound the way an atom relates to an element. Most matter on earth, including food, is a mixture of different chemical compounds.
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The electrical attractions between protons and electrons are the most important driving force behind all of the chemical activity that makes life and cooking possible. Protons carry a positive electrical charge and electrons carry an exactly balancing negative charge. Neutrons are neutral and they carry no charge. Opposite electrical charges attract one another, while similar electrical charges repel one another. The electrons in atoms are arranged around the nucleus in orbits that determine how strongly any particular electron is held there.
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The closer an electron orbits the nucleus the stronger the bond. The farther away an electron orbits the nucleus, the weaker the bond.
One of the most important elements that readily grabs electrons is oxygen. It is done so much that scientists have given it a name called oxidation. Oxidation is the general chemical activity of grabbing electrons from other atoms. Oxidation can still happen even if oxygen is not involved. With oxygen always present in the air, it is very important in the kitchen. Oxygen eagerly steals the electrons from the carbon-hydrogen chains of fats, oils and aroma molecules. The preliminary oxidation triggers a cascade of further oxidations and other reactions that end up breaking the original large fat molecules into small, strong smelling fragments. This is can be an indication that something has gone bad. Antioxidant substances can prevent this breakdown by giving oxygen the electrons that it wants without starting a cascading reaction.
An interaction between atoms or molecules that holds them together, either loosely or tightly, momentarily or indefinitely is called a chemical bond. This is important because there are several types of chemical bonds that are in nature as well as in the kitchen.
The ionic bond is one kind of chemical bond in which one atom completely captures the electron(s) of another atom. Chemical compounds which are held together by ionic bonds readily dissolve in water. However, to do so they must come apart into separate ions, which are atoms that are electrically charged because they either carry extra electrons or gave up some of their electrons. One of the most common seasonings, salt, is a compound of sodium and chlorine held together by ionic bonds. Pure salt as a solid crystal is positively charged sodium ions alternate with negatively charged chloride ions. The sodiums in salt have lost their electrons to the chlorines. When salt is dissolved in water, it separates into positive sodium ions and negative chloride ions.
A second type of chemical bond is called a covalent bond. A covalent bond produces stable molecules. When two atoms have roughly similar affinities for electrons, they will share them rather than gain or lose them entirely.
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The elements most important to life on earth: hydrogen, oxygen, carbon, nitrogen, phosphorus, and sulfur, all tend to form covalent bonds.
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These bonds make possible the very complex, stable assemblages that make up our bodies and our food. Water, probably the most well known pure chemical compound in the kitchen, is made up of two hydrogen atoms and one oxygen atom. Another well known chemical compound found in the kitchen is sucrose, or table sugar. Sugar has a combination of carbon, oxygen, and hydrogen atoms. Covalent bonds are typically very strong and stable at room temperature. They are usually not broken in significant numbers unless subjected to heat or reactive chemicals. Covalent bonds are different from ionic bonds (salt) because when they dissolve in water, they remain intact as electrically neutral molecules.
A third type of chemical bond is the hydrogen bond. A hydrogen bond is about a tenth as strong and stable as covalent bonds. There are several "weak" bonds and the hydrogen bond is one of them. These "weak" bonds do not form molecules, but they do make temporary links between different molecules, or between different parts of one large molecule. A hydrogen bond is very important because it is very common in materials that contain water. Thus it brings different kinds of molecules into close association, and because it is weak enough, these molecular associations can change rapidly at room temperature. Many of the chemical interactions in plant and animal cells occur via hydrogen bonds.
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A fourth type of chemical bond is the van der Waals bond. This is a very weak bond and is between a hundredth and a ten thousandth as strong as a covalent bond. Thanks to brief fluctuations in their structures, van der Waals bonds have flickering attractions that even nonpolar molecules can feel for each other. Nonpolar fat molecules are held together as a liquid and given its thick consistency by van der Waals bonds. Van der Waals bonds are very weak, but their effect can add up to a significant force. This is achieved because fat molecules are long chains and they include dozens of carbon atoms. Thus, each fat molecule can interact with many more other molecules than a small water molecule can.