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40 Cards in this Set
- Front
- Back
experiments
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systematic observations or measurements, preferably made under controlled conditions
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hypotheses
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tentative explanations for scientific observations
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laws
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verbal or mathematical descriptions of a phenomenon that allows for general predictions. A law says what happens, not why it happens
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theories
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statements that attempt to explain why nature behaves the way it does. They tend to be incomplete and imperfect, evoloving with time to explain new facts as they are discovered
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scientific method
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the procedure scientists use to search for answers to questions and solutions to problems
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mass
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the quantity of matter an object contains: mass is a fundamental property of an object that does not depend on its location
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gas
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one of the three disinct states of matter under normal conditions, gases have neither fixed shapes nor fixed volumes and expand to fill their containers completely
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liquid
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liquids have a fixed volume but flow to assume the shape of their containers
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solid
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solids are relatively rigid and have fixed states and volumes
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mixtures
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a combination of two or more pure sustances in variable proportions in which the individual substances retain their identities
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homogenous mixture
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a mixture in which all portions of the material are in the same state, have no visible boundaries and are uniform throughout (koolaid)
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heterogeneous mixture
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a mixture in which a marterial is not completely uniform (chocolate chip cookies)
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elements
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a pure substance that cannot be broken down into simpler ones by chemical changes
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physical properties
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a characteristic that scientists can measure without changing the composition of the sample under study (mass, color, volume)
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chemical properties
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the characteristic ability of a substance to react to form new substances
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intensive property
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a physical property that does not depend on the amount of the substance (color, boiling point, melting point)
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extensive property
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a physical property that varies with the amount of the sustance (mass, weight, volume)
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density
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mass/volume an intensive property of matter, mass per unit volume
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atoms
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the fundamental, indivisible particles of which matter is composed
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electrons
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a subatomic particle with a negative charge
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nucleus
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the central core of an atom, where protons and any neutrons reside, comprises most of the mass of an atom but very little volume
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protons
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positive charge, opposite of the electron
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radioactivity
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the spontaneous emission of energy rays by matter
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atomic number
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(z) the number of protons in the nucleus of an atom of an element, the atomic number is different for each element
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isotopes
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atoms that have the same number of protons and hence the same atomic number (Z) but different numbers of neutrons
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mass number
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(A) the number of protons and neutrons in the nucleus of an atom of an element. Isotopes in an element only differ in their atomic mass
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atomic mass unit
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(amu) 1/12 of the mass of one atom of 12C
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ion
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a charged particle produced when one or more electrons is removed from or added to an atom or molecule
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periodic table
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a chart of the chemical elements arranged in rows of increasing atomic number so that the elements in each column (group) have similar chemical properties
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groups
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any of the vertical columns of elements in the periodic table
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periods
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the rows of elements in the periodic table
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alkali metals
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any of the elements in group 1 of the periodic table. All are metals that react readily with nonmetals to give ions with a +1 charge
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alkaline earths
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the elemeents in group 2 of the periodic table that all react readily with nonmetals to give ions a +2 charge
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noble gases
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any of the elements in group 18 of the periodic table that are all unreactive monatomic gases at room temperature and pressure
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halogens
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any of the elements in group 17 that all react readily with metals to give ions with a -1 charge
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metals
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any of the elements to the left of the zigzag line in the periodic table, can be hammered into thin sheets, pulled into wires, most are shiny, all except mercury are solids at room temperature
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nonmetals
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any of the elements to the right of the zigzag line, poor conductors of electricity, not shiny, not malleable, not ductible
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semimetals
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have properties between those of metals and nonmetals
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main group elements
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any of the elements in groups 1, 2 and 13-18
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essential element
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any of the 19 elements that are absolutely required in the diets of humans in order for them to survive
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