Act8_sol - 12/12/05 Activity 8 Solutions: Chemical Energy...

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12/12/05 1 Activity 8 Solutions: Chemical Energy 8.1 What is the Composition of Matter? 1) Atoms a) What are the building blocks of an atom? An atom consists of a positively charged nucleus surrounded by negatively charged electrons. b) What is an atomic nucleus? The nucleus is the part of the atom made up of protons and neutrons. The nucleus, which is at the center of the atom, comprises 99.9% of the atom’s mass, while it only takes up roughly one ten-thousandth of the volume of a typical atom. c) What is a nucleon? A positively charged proton or a neutral neutron d) What holds nucleons together within the nucleus of an atom? The strong nuclear force holds together the nucleons (even though the protons are electrically repulsed by each other.) e) How many electrons does an atom have? How many electrons does an ion have? An atom has no net electric charge, so the number of electrons surrounding the nucleus equals the number of protons in the nucleus. An ion has a net electric charge, so the number of electrons in an ion is not equal to the number of protons. f) What holds electrons in orbit around the nucleus of an atom? As noted above, electrons are negatively charged, protons are positively charged, and neutrons are electrically neutral. The electrostatic force of attraction between the protons and electrons holds the electrons in orbit. g) What is an element? An element is matter made up of atoms which all contain the same number of protons. Each element has a name and occupies a place on the periodic table. 2) An Atomic Model a) The two foam balls connected by wires simulate the forces between two protons. What force do the springy wires represent? electromagnetic force What force do the magnets represent? strong nuclear force b) From the model, does the strong nuclear force act over a long or a short range? The strong force acts over a very short range.
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12/12/05 2 c) Group Discussion Question: How could the model be modified to make it represent a neutron and a proton? How could it be modified to represent two neutrons? 8.2
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Act8_sol - 12/12/05 Activity 8 Solutions: Chemical Energy...

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