chapter 1 Flashcards
define chemistry
the science that seeks to understand the behavior of matter by studying atoms and molecules
what system is used for units?
- Use the metric system
* Kelvin used for temp, 273K = 0 Celsius
define mass
Mass is the quantity of matter (g)
define weight
• Weight is the force of gravity (kg)
how are mass and weight related?
• Weight is proportional to mass
what are derived units?
• Derived Units are a combination of units
is mass derived or fundamental? weight?
- Mass is fundamental
* Weight is derived
what is volume?
Volume is a measure of space
how many ml are in a cubic cm?
1 mL = 1cm^3
how many L are equal to a cubic meter?
1000 L = 1 m^3
how many ml are in a L?
1L = 1000 mL
how many cubic cm are in a L?
1L = 1000cm^3
what do extensive properties rely on?
Extensive = value depends on quantity
what do intensive properties rely on?
value is independent of quantity of matter
• Used to identify type of matter
• Identical intensive properties = same material
does density have derived units or fundamental? what is density?
derived
ratio of mass to volume (m/v)
• g/L (gas), g/cm^2 (solid), g/mL (liquid)
what is percent composition?
alternate way to describe a mixture
% by volume formula
volume of component A/ total vol of mixture X 100%
% by mass formula
- % mass - mass of component A/total mass of mixture X100%
in a mixture what does A + B = ?
100%
how are small numbers dealt with?
prefix multipliers (ie mg), scientific notation
what is precision?
- Precision: how close replicated measurements are to one another (random error)
- One way to quantify is to calculate the standard of deviation of replicated measurements (smaller = more accurate)
what is accuracy?
• Accuracy is the agreement of a measured value with the true/accepted value (systematic error)
describe use of sig figs. what digits are included?
• All measurements have an amount of uncertainty
• Sig figs include all digits (certain) including the first uncertain digit
• When publishing results we must report all data to the corrects sig figs
Thus # of sigfigs is an indication of the instruments finest graduation (ie sensitivity limit)
what is the number of sig figs an indicator of?
the number of significant figures is understood
to be an indication of the instruments finest graduation
(i.e. its sensitivity limit).
which digit is uncertain?
• In any measurement each digit we include is certain,
except the last, which is an estimate
• The number of sig figs indicates the precision of an
instrument
how is measurement precision last digit assumed?
assumed to be ±1 in the last digit
• The more digits an instrument provides the higher the
precision
- this also means a measurement has a smaller range of
expected values
rules for adding and subtracting
Addition and Subtraction: The answer has the
same number of decimal places as there are in the
measurement with the fewest decimal places
rules for multiplying and dividing
Multiplication and Division: The answer contains
the same number of sig figs as there are in the
measurement with the fewest significant figures
rules for mixed operations
Follow order of operations. Carry out the operations
within the brackets first; retain a few extra digits to
prevent rounding errors; round the final answer to the
correct number of significant figures
what is an exact number?
A number whose value is known with complete certainty
is exact
• from counting individual objects
• from defined quantities
• Exact numbers have an unlimited number of significant
figures
