問題一覧
1
Observation
carefully noting and recording changes during an experiment
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A law
describe a consistent, observable relationship in nature, based on repeated experimental observations
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A theory
provides a coherent and comprehensive understanding of a set of phenomena or observations
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Matter is
anything that has mass and take up space including liquids
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Solids
(definite volume and shape)
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Liquids
(definite volume but no define shape)
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Gases
(no definite volume nor shape)
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Element
made of one type of atoms
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Compound
a molecule that is made of 2 or more elements
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Homogeneous mixture
mixtures of evenly distributed substances (cannot tell it is a mixture)
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Heterogeneous mixture
mixtures of unevenly distributed substances (can tell it is a mixture)
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Chemical change
changes the identity of the substance( wood burning to form ashes and smoke)
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Physical change
changes that don’t change the identity of the substance except color chnage ( an ice cube(solid)melts to water(liquid))
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Potential energy
energy that is stored
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Kinetic energy
the energy of motion
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Exothermic
releases heat energy
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Endothermic
absorbs heat energy
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Daltons atomic theory
•the atoms of each element are unique •atoms are unchanged in chemical reactions
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Nuclear theory of the atom
•electrons orbit the nucleus •nuclear forces hold the nucleus together •nucleus determines atomic identity
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What is an ion
when a neutral atom (no charge) gains or loses electrons
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3 main types of radioactive decay
•alpha particles •beta particles •gamma rays