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Accuracy
How closely a measure value agrees with the correct value.
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Atom
The smallest particle of an element that maintains its chemical identity through all chemical and physical changes.
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Atomic number
The number of protons in the nucleus of an atom.
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Calorie
Defined as exactly 4.184 joules. Originally defined as the wmount of heat required to raise the temperature on one gram of water from 14.5 degreesC to 15.5 degrees C.
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Chemical change
A change in which one or more new substances are formed.
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Chemical property
see properities
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Compound
A substance composed of two or more elements in fixed proportions. Compounds can be decomposed into their constituent elements.
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Density
Mass per unit volume, D=m/V.
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Element
A substance that cannot be decomposed into simpler substances by chemical means.
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Endothermic
Describes processes that absorb heat energy.
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Energy
The capacity to do work or transfer heat.
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Exothermic
Describes processes that release heat energy.
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Extensive property
A property that depends on the amount of material in a sample.
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Heat
A form of energy that flows between two samples of matter because of their difference in temperature.
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Heat capacity
The amount of heat required to raise the temperature of a body one degree Celsius.
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Heterogeneous mixture
A mixture that does not have uniform composition and properties throughout.
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Homogeneous mixture
A mixture that has uniform composition and properties throughout.
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Intensive property
A property that is independent of the amount of material in a sample.
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Joule
A unit of energy in the SI system. One joule is 1kg*m2/s2, which is also 0.2390 cal.
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Kinetic energy
Energy that matter possesses by virtue of its motion.
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Law of Conservation of Energy
Energy cannot be created or destroyed in a chemical reaction or in a physical change; it may be changed from one form to another.
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Law of Conservation of Matter
No detectable change occurs in the total quantity of matter during a chemical reaction or during a physical change.
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Law of Conservation of Matter and Energy
The combined amount of matter and energy in the universe is fixed.
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Law of Constant Composition
See Law of Definite Proportions
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Law of Definite Proportions
Different samples of any pure compound contain the same elements in the same proportions by mass; also known as the Law of Contant Composition.
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Mass
A measure of the amount of matter in an object. Mass is usually measured in grams or kilograms.
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Matter
Anything that has mass and occupies space.
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Mixture
A sample of matter composed of variable amounts of two or more substances, each of which retains its identity and properties.
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Molecule
The smallest particle of an element or compound that can have a stable independent existence.
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Physical change
A change in which a substance changes from one physical state to another, but no substances with different compositions are formed.
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Physical property
See Properties.
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Potential energy
Energy that matter possesses by virtue of its position, condition, or composition.
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Precision
How closely repeated measurements of the same quantity agree with one another.
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Properties
Characteristics that describe samples of matter. Chemical properties are exhibited as matter undergoes chemical changes. Physical properties are exhibited by matter with no changes in chemical composition.
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Scientific (natural) law
A general statement based on the observed behavior of matter, to which no exceptions are known.
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Significant figures
Digits that indicate the precision of measurements--digits of a measured number that have uncertainty only in the last digit.
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Specific gravity
The ratio of the density of a substance to the density of water at the same temperature.
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Specific heat
The amount of heat required to raise the temperature of one gram of a substance one degree Celsius.
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Substance
Any kind of matter all specimens of which have the same chemical composition and physical properties.
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Symbol (of an element)
A letter or group of letters that represents (identifies) an element.
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Temperature
A measure of the intensity of heat, that is, the hotness or coldness of a sample or object.
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Unit factor
A factor in which the numerator and denominator are expressed in different units but represent the same or equivalent amounts. Multiplying by a unit factor is the same as multiplying by one.
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Weight
A measure of the gravitational attraction of the earth for a body.
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