Chem 120: Exam 1 Chapters 1-4 Key
Terms.| Questions and Answers
chemistry - -the study of matter and the changes it undergoes
- matter - -anything that has mass and occupies space (made up of atoms &
molecules)
- element - -basic material that can not be broken down into simpler
substances
- compound - -chemical combination of two or more elements into new
substance
- Standard Notation - -a value is written with one non zero digit to he left of
the decimal point and all other digits to the right (coefficient). this number is
multiplied by 10 raised to the appropriate power (exponent). Has to be
greater than 1 but less than 10
Ex. 3500--> 3.5 x 10^3
- measurement - -the quantity, dimensions, or extent of something (usually
compared to a specific unit)
ex. 2 parts (number + unit): 26.5 kg
- unit - -a definite quantity adopted as a standard of measurement
- measured numbers - -numbers obtained through some kind of
measurement--> have uncertainty & significant figures
- significant figure (sig. fig.) - -a digit that is either reliably known or closely
estimated
ex. i have 2 cats, theres 18,000 students at JMU
- exact numbers - -numbers obtained by counting or defined equality. These
are not measured, have infinite sig figs, and has no uncertainty
- certainty - -degree of certainty in a measurement
Ex. 18,270 is more certain than 18,000
- uncertainty - -degree of reproducibility in a series of measurements
ex. measuring the temp. outside multiple times
- accuracy - -how close a measurement is to the true value
, -it is best to take multiple measurements and average them, the accuracy is
then based on the average of the measurements
- conversion factor - -relationship between two equal quantities written as a
fraction
-are equivalent to their inverses because both are equal to 1 (numerator =
denominator)
ex. 1 min= 60 s
- dimensional analysis - -conversion of a measurement in one unit into
another by the use of conversion factors
ex. given unit x conversion factor(s)= desired unit
- density - -the ratio of a substance's mass to its volume
-can be used to identify a substance because it is an intensive property
(constant for the same substance)
ex. D=m/v
- specific gravity - -the ratio of the density of a substance to the density of
water, has no units
- pure substance - -matter that has a fixed composition and definite
constant properties
- element - -the simplest form of matter
-composed of only one type of material
-made up of atoms
ex. Chlorine, Hydrogen
- compound - -composed of 2 or more elements chemically combined
always in the same proportion, made up of molecules- particles in which
atoms are held together by chemical bonds
- mixture - -two or more substances which are physically (NOT chemically)
combined
-properties of each of the original components can still be observed, thus
they can be physically separated because there's no chemical bonds
between the particles
ex. coffee, air, steel, trail mix
- Homogenous Mixture - -uniform composition throughout the samples "see
through"
-one state of matter
ex. salt, brass, air, apple juice
Terms.| Questions and Answers
chemistry - -the study of matter and the changes it undergoes
- matter - -anything that has mass and occupies space (made up of atoms &
molecules)
- element - -basic material that can not be broken down into simpler
substances
- compound - -chemical combination of two or more elements into new
substance
- Standard Notation - -a value is written with one non zero digit to he left of
the decimal point and all other digits to the right (coefficient). this number is
multiplied by 10 raised to the appropriate power (exponent). Has to be
greater than 1 but less than 10
Ex. 3500--> 3.5 x 10^3
- measurement - -the quantity, dimensions, or extent of something (usually
compared to a specific unit)
ex. 2 parts (number + unit): 26.5 kg
- unit - -a definite quantity adopted as a standard of measurement
- measured numbers - -numbers obtained through some kind of
measurement--> have uncertainty & significant figures
- significant figure (sig. fig.) - -a digit that is either reliably known or closely
estimated
ex. i have 2 cats, theres 18,000 students at JMU
- exact numbers - -numbers obtained by counting or defined equality. These
are not measured, have infinite sig figs, and has no uncertainty
- certainty - -degree of certainty in a measurement
Ex. 18,270 is more certain than 18,000
- uncertainty - -degree of reproducibility in a series of measurements
ex. measuring the temp. outside multiple times
- accuracy - -how close a measurement is to the true value
, -it is best to take multiple measurements and average them, the accuracy is
then based on the average of the measurements
- conversion factor - -relationship between two equal quantities written as a
fraction
-are equivalent to their inverses because both are equal to 1 (numerator =
denominator)
ex. 1 min= 60 s
- dimensional analysis - -conversion of a measurement in one unit into
another by the use of conversion factors
ex. given unit x conversion factor(s)= desired unit
- density - -the ratio of a substance's mass to its volume
-can be used to identify a substance because it is an intensive property
(constant for the same substance)
ex. D=m/v
- specific gravity - -the ratio of the density of a substance to the density of
water, has no units
- pure substance - -matter that has a fixed composition and definite
constant properties
- element - -the simplest form of matter
-composed of only one type of material
-made up of atoms
ex. Chlorine, Hydrogen
- compound - -composed of 2 or more elements chemically combined
always in the same proportion, made up of molecules- particles in which
atoms are held together by chemical bonds
- mixture - -two or more substances which are physically (NOT chemically)
combined
-properties of each of the original components can still be observed, thus
they can be physically separated because there's no chemical bonds
between the particles
ex. coffee, air, steel, trail mix
- Homogenous Mixture - -uniform composition throughout the samples "see
through"
-one state of matter
ex. salt, brass, air, apple juice
