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Science
a body of knowledge about the natural world
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theory
a general set of principles, supported by evidence,that explains some aspect of nature
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scientific method
- a means of coming to understand the natural world through observation and the testing of hypotheses
- observation, question, hypothesis, experiment, conclusion
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hypothesis
a tentative, testable explanation for an observed phenomenon
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variable
an adjustable condition in an experiment
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biology
the study of life
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characteristics of living things:
- Can assimilate (take in) and use energy
- Can respond to their environment
- Can maintain a relatively constant internal environment
- Possess an inherited information base, encoded in DNA, that allows them to function
- Can reproduce through use of the information encoded in DNA
- Are composed of one or more cells
- Evolved from other living things
- Are highly organized compared to inanimate objects
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life sciences
a set of disciplines that focus of varying aspects of the living world
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evolution
the gradual modification of populations of living things over time, with this modification sometimes resulting in the development of new species
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mass
a measure of the quantity of matter in any given object
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protons
positively charged subatomic particles, packed tightly with neutrons in the atom's nucleus
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neutron
neutrally charged subatomic particles, protons and neutrons make up an atom's nucleus
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electron
negatively charged subatomic particle that moves around the atom's nucleus
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nucleus
protons and neutrons tightly packed together forms the core of atoms
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element
- a substance that is pure in that it cannot be reduced to any simpler set of component substances through chemical processes
- the thing that defines each element is the number ofprotons it has in its nucleus
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atomic number
the number of protons in an element's neucli
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isotopes
the number of neutrons in an elements nucleus may vary, we can have various forms of elements
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chemical bonding
- When the outermost electrons of two atoms come into contact, it becomes possible for these electrons to reshuffle themselves in a way that allows the atoms to become attached to one another
- Two types:
- ionic bonding
- covalent bonding
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covalent bonding
a chemical bond in which atoms share pairs of electrons
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ionic bonding
Giving up electrons
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law of conservation of mass
matter is neither created nor destroyed in a chemical reaction
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molecule
an entity consisting of a defined number of atoms covalentlybonded together
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the oxygen atom has greater power to attract electrons to itself than do the hydrogen atoms. The term for measuring this kind of pull is:
electronegativity
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polarity
difference in electrical charge at one end as opposed to the other
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Because electrons are negatively charged and because they can be found closer to the oxygen nucleus, the oxygen end of the molecule becomes slightly negatively charged,while the hydrogen regions become slightly positively charged. We still have a covalent bond, but it is a specific type:
polar covalent bond
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With the hydrogen molecule where electrons are shared equally we have a:
nonpolar covalent bond
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ion
a charged atom or, to put it anotherway, an atom whose number of electrons differs fromits number of protons
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ionic bonding
a chemical bonding inwhich two or more ions are linked by virtue of their opposite charge
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molecular formula
A chemical formula that shows the total number and kinds of atoms in a molecule, but not their structural arrangement. For example, the molecular formula of aspirin is C9H8O4
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