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CEM 141 Chapter 1 Learning Objectives (1)
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CEM 141 Chapter 1 Learning ObjectivesAtoms: the smallest unit of ordinary matter that forms a chemical element
Molecules: electrically neutral group of two or more atoms held together by chemical bonds.
Elements: consists only of the same atoms, with the same number of protons
Compounds: a chemical substance composed of atoms from 2+ elements held together by
chemical bonds - ANS-Identify and explain the similarities and differences between atoms,
molecules, elements, and compounds
Claim: atoms are the smallest unit of matter that forms an element and make up everything in
the world
Evidence: an example is water, which is a liquid we drink and makes up more than half our
body.
Reasoning: water is made up of hydrogen and oxygen atoms, we know this because they can
be boiled and evaporate into the air and can be separated/added to each other. - ANS-Make an
argument(claim, evidence, reasoning) for the existence of atoms
Claim: electrons are subatomic particles within an atom which hold a negative charge
Evidence: JJ Thompson used a cathode ray tube to prove the existence of electrons. This CRT
was connected to metal discs coated with a chemical that responds to electric and has wires
embedded inside.
Reasoning: with his CRT, he found that the rays were negatively charged, emerged from one
end and moved to the other, can be deflected by magnetic fields, carried an electric charged
which bent the rays present in the CRT, and found the metal did not affect the ray behavior. He
concluded the charge must come from inside the atoms with this data and developed the plum
pudding model with it. - ANS-Make an argument(claim, evidence, reasoning) for the existence of
electrons
Claim: a nucleus is a subatomic particle inside an atom.
Evidence: Rutherfords experiment using helium atoms which he projected onto a gold foil.
Reasoning: most of the particles(He atoms) went straight through the foil. However, some atoms
were deflected off the foil and an even smaller amount bounced right back to where they were
initially projected from. This is because of the bigger nuclei inside gold atoms which the He at
times would come into contact with, causing them to deflect. The nucleus must exist or else the
He atoms would not have been deflected, and all of them would have gone straight through.
(nucleus positive because electrons of He repel it, it is small because MOST went through) -
ANS-Make an argument(claim, evidence, reasoning) for the existence of the existence of a
small, massive, and positively charged nucleus
In everyday use, the word "theory" often means an untested hunch, or a guess without
supporting evidence. But for scientists, a theory has nearly the opposite meaning. ... A theory
not only explains known facts; it also allows scientists to make predictions of what they should
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