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Transcript
Chemistry—An Introduction Chapter 2 Pages 25-33 Matter Occupies space and has mass Mass is NOT the same as weight States of matter Solid Liquid Gaseous Energy Can only be measured by effect on matter Defined as: The capacity to do work Two types Kinetic energy Potential energy Forms of Energy Chemical energy Electrical energy Mechanical energy Electromagnetic energy All forms are easily convertible Elements and Atoms All matter composed of elements Elements composed of atoms Cannot be broken down Ex: Oxygen, Carbon, Gold, Silver, Copper, Iron Unique in each element Atomic symbol Abbrev. for element O = Oxygen, C = Carbon Atomic Structure Atoms contain smaller structures Nucleus Electrons (e-) Most dense and most of mass of atom (1amu) Neutrons (n0) Protons (p+) Tiny, 1/2000 mass of protons and neutrons Equal number of protons and electrons Identifying Elements Atomic Number = to number of protons in a nucleus Written as subscript to Left of atomic symbol Ex: (1H); (2He) Mass Number = to sum of masses of protons + neutrons Written as superscript to Left of atomic symbol Ex: H mass number = 1(p+) + 0 (n0) = 1 He mass number = 2 (p+) + 2 (n0) = 4 Now know total numbers of all subatomic particles Structural variations Called isotopes Differ in number of neutrons Atomic Weight Avg of mass numbers of all isotopes of an element Also takes into account relative abundance Ex: H atomic wt. = 1.008 Molecules and Compounds Molecule Two or more atoms held together by a chemical bond Compound Two or more different atoms held together by a chemical bond Chemically pure Mixtures Composed of two or more substances that are physically mixed Three types: Solutions Colloids Suspensions Solutions Homogeneous mixtures Solvent Substances present in greater amt Solute Present in smaller amts Concentration of Solutions Described in terms of % of the solute in solution Can also describe in terms of molarity (moles per liter) (M) Mole = to molecular weight Avogadro’s number = 6.02 x 1023 Makes sure that the substance always contains exactly same number of solute particles Colloids Heterogeneous mixtures Appear milky Ex: Jello-O, cytosol Suspensions Heterogeneous mixtures Contain lg solutes that settle out Ex: Sand and water Ex: Blood Mixtures vs. Compounds No chemical bonding occurs between components of a mixture Mixtures can be separated by physical means; compounds cannot Mixtures can be hetero- or homogeneous; compounds are only homogenous