Ch02

Biology (5th Edition)

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Unformatted text preview: 1 3 states of matter on earth: solid, liquid, gas Greeks believed these 4 were pure substances; could not be broken down further Many forms with various characteristics; wood, glass, rocks, metals… Matter- anything that takes up space & has mass Elements-a substance that cannot be broken down to other substances by chemical reactions. Ancient Greeks believed there were 4 :air, water, fire, & earth Plasma -4th state of matter found in stars & gas planets; rapidly moving gas mol. 92 naturally occurring elements Compound- a substance consisting of 2 or more elements in a fixed ratio. Life Requires 25 Chenical Elements Na is a metal by itself; Cl a poisonous gas A compound has characteristics beyond those of its combined elements. Ex: 1:1 ratio of NaCl; table salt % h. body weight: H-65% O-18.5% N-9.5% C-3.3% .1-1.5%: CaM g PS & NaCl Trace elements: <.1%: B,Cr,Co,Cu,F,I,Fe Mn,Mo,Se,Si,Sn, V, & Zn Chemical Elements and Compounds Chapter 2 2 Neutrons-in nucleus, no charge, 1 Dalton Ex: 2 He # protons=2 atomic #=2 Electrons- outside nucleus, 1- charge, 1/2000 of a Dalton (=0 D) Subatomic particles Atomic # Denotes # of protons (same for every atom of that element, always!) Protons-in nucleus, 1+ charge, 1 Dalton In an electrically neutral atom, atomic # also = # of electrons Atomic weight (mass) Isotopes- atoms that have a different # of neutrons than atoms...
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Ch02 - 1 3 states of matter on earth: solid, liquid, gas...

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