CHemistry chapter 2 2
Terms
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- scientific method
- a logical approac to solving problemsby observing and collectiong data, formulating and testing hypothesis, and formulating theories that are supported by data.
- observing
- the use of senses to obtain information it involves measurements and collecting data.
- Qualative vs. quantitative information
- Qualative is descriptive and quantitative is numerical
- a system is a
- a apecific protion of matter ina given region of space that has been selected for study during an experiment.
- hypothesis
- a testable statement
- model
- used to represent ideas which cannot be easily viewed
- theory
- broad generalizations used to explain observations.
- quantity
- something that has magnitude, size or amount
- SI system
- the system internationale which includes 7 base units, also known as the metric system
- measurement standard
-
an object or natureal ohenomena that is of constant balue, easy to preserve and reproduce, and pratical in size
-a means of comparison -
length
mass
time
temperature
amount of substance
electric current
luminous intensity
energy -
meter
kilogram
second
kelvin
mole
ampere
candela
jule - Celsius to Kelvin
- degree C + 273 =K
- king henry died (monday)(laughing) (greedy) drinking chocolate milk
-
km-hm-dam-m-dm-cm-mm
kl-hl-dal-l-dl-cl-ml
kg-hg-dag-g-dg-cg-mg - dimensional analysis or factor label method
- method of solving problems based on cancellation of units
- formula for density
-
D=m/v
density equals mass divided by volume - how do you find the volume of irregularly shaped objects
- water displacement
- volume of cylinders
- V= pi(r)2(h)
- what is accuracy
- closeness to the read value
- what is precision
- repeatability of a measurement, how many times you come close.
- percent error is calculated by
- value (accepted)- value(experimental)/ value(accepted) x 100.
- significant figures are
- valid figures actually obtained form a measurement.
- what are the rules for determining the number of significant figures.
-
- all nonzero digits are significant
-leading zeros are not significant
-captive zeros are significant
-trailing zeros may or may not be significant - exact and perfect numbers
- measurements or counting and are infinite number of solutions.
- what is a graph
- a picture of data
- rules for making a good graph are
-
-you label each axis with a unit and a description
-divide each axis evenly
-plot and circle data points
-draw a best fit line between data points - how do you find the slope
- rise over run
- direct and indirect proportions
-
direct- when one goes up the other quantity goes up too
indirect- when one goes up the other goes down.(hyperbola) - conversion factor
- a ratio derived from the equality between two different units that can be used to convert from one unit to the other.