Exam #2 Flashcards
What types of errors cause uncertainty in measurements?
- instrument error
- human error
- method error
example of an instrument error
not calibrated, broken, missing an increment
example of human error
reading a measurement incorrectly/not reporting data to the correct uncertain digit
example of method error
not reading meniscus properly, not using standard method
what is the difference between accuracy and precision?
accuracy is how reliable the measurements are and precision is how finely the measurements are made
what are significant figures?
all the certain numbers plus one uncertain digit
what is the purpose of significant figures?
they help to determine the uncertainty of a measuring instrument which allows you to determine the precision of the instrument
how do you determine precision of a lab instrument?
the lower the amount of uncertainty the greater the relative precision
what does the SI system stand for?
international system of units
who uses the SI system and why?
the scientific community, provides a standard comparison for measurement when conducting research/ allows the community to share research without needing conversions and errors
what 2 advantages does the SI system have when doing calculations?
- it is based on the power of 10 so conversions are easier (moving decimal place)
- measurements are in decimal form so calculations are easier
What are the 4 fundamental SI base units and their symbols for mass, length, time and temperature?
mass- kilogram (kg)
length- meter (m)
time- seconds (s)
temp.- Kelvin (K)
what is the difference between heat and temperature?
temp. -measures the kinetic energy of a sample and does not rely on the samples mass
heat- refers to the total amount of energy in a sample available to transfer from an object with a higher temp to an object with a lower temp., (KE and PE), depends on the mass of the sample
what instrument is used to measure temp.?
thermometer, lab unit is celsius
what instrument is used to measure heat?
a calorimeter, SI unit- joules , non-SI- calories
what does density depend on?
temp. and pressure (gases only)
why is water the exception of density?
particles in the solid phase of water are in a fixed position so positives arent next to positives and negatives arent next to negatives, H2O molecules are spread farther apart in the solid state than the liquid state, water expands as it freezes
why is density usually D(s)-D(l)-D(g)?
as heat energy is input into a phase to change it, the particles increase in kinetic energy which increases the temp. up until the melting/boiling point where the particles will increase in potential energy and increase the distance between them. Dependent on how close the particles are packed together in a certain volume
