Chem Notes - Intro to General Chem ← ← Only 88 naturally occurring elements that are non radioactive ← Elements in the human body • Trace

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Unformatted text preview: Intro to General Chem ← ← Only 88 naturally occurring elements that are non radioactive ← Elements in the human body • Trace Elements are important o Hemoglobin o Zinc Element that is essential to all forms of life Variety of enzymes have tetrahedral structure ← ← Examples of Applications of Chem in Agriculture • Haber Process o Reaction of nitrogen and hydrogen to produce ammonia o Employs a iron catalyst at high temperatures (450-500 Celsius) and pressures (200 atm) o Described as the most important invention of the 20 th century because it helps with fertilizers which helps us produce food o o responsible for producing 500 million tons of artificial fertilizer per year and is responsible for sustaining 40% of the earth’s population • Penicillin o WW2 for traeating infections o • Taxol o • Cisplatin o “penicillin of cancer drugs” o inorganic molecule with a simple structure o • Plastics… Elements, Compounds, and mixtures • Elements o Type of matter that is composed of atoms with the same atomic number (ie. The number of protons in their nuclei) o A substance is an element if its composition corresponds to only ONE of the symbols of the periodic table • Allotropes o Different forms of the same element in the same phase (liquid, solid, or gas) Oxygen: dioxygen and ozone 05/09/2007 08:42:00 ← Compounds • A substance that contains two or more elements in chemical combination o Binary Composed of only two elements, aka water • Mixtures o A combination of two or more elements or compounds Aka Brass (Cu + Zn), Salt Water (NaCl + H20) o Either heterogeneous or homogenous Heterogeneous mixture can be easily separated into components Homogenous mixture is a mixture that cannot be easily separated by common physical means • Pure substance can be EITHER an element, OR a compound. Word material is a term to refer to a sample of unknown composition and may be a pure substance or mixture • ← ← Indirect Evidence for the Existence of Atoms: The Laws of Chemical Combination • First evidence of atoms was obtained by analyzing the respective weights of products and reactants which led to two laws: o Law of Conservation of Mass (Lavoisier) o Law of Definite Proportions (Proust) In a pure compound, the constituent elements are always present in a definite proportion or % by weight. The relative weights are fixed. • Dalton’s Atomic Theory of Matter (1808) o Matter consists of indivisible atoms This notion that matter becomes “not divisible” s critical for explaining the consistence of composition, and on that basis, Dalton postulated the existence of the atom o All atoms of a given element are identical in mass and other properties (note that today we know that this is incorrect because of isotopes) o Different elements have different kinds of atoms which have different masses o Atoms are indestructible and retain their identities in chemical reactions (Law of conservation of mass = conservation of atoms)...
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This note was uploaded on 04/30/2008 for the course CHEM 1411 taught by Professor Parkin during the Spring '08 term at Columbia.

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Chem Notes - Intro to General Chem ← ← Only 88 naturally occurring elements that are non radioactive ← Elements in the human body • Trace

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