Quiz 1 Flashcards
Hypothesis
a tentative explanation or prediction concerning some phenomenon
Scientific Law
a summary of observed patterns in large collections of data (often expressed mathematically)
Theory
provides explanations of observed natural phenomena and predictions that can be tested by further experiments
Qualitative
Descriptive
Quantitative
Measurements
kilo-
10^3
centi-
10^-2
milli-
10^-3
nano-
10^-9
micro-
10^-6
Volume
l x w x h = cm^3
Intensive Properties
Independent of sample size
- temperature
- melting point
- density
Extensive Properties
Dependent of sample size
- volume
- length
- mass
Density
the mass per unit volume of a substance
dependent on temperature
equation
d=m/v
units of density for chemistry
- solids g/cm^3
- liquids g/mL
- gases g/L
Energy
ability to cause a change in a physical system
accuracy
how close to the true value a given measurement
-percent error
[(average exp value - true value) / true value] x 100
precision
how well a number of independent measurements agree with each other
(characterized by standard deviation)
Significant Figures
- zeros between two other significant digits are significant ( 107 / 1.209 x 10^-7)
- a lone zero proceeding a decimal point is not significant (0.749)
- zeros between the decimal point and the first non-zero digit are not significant (0.03739)
Significant Figure Rules
- zeros between two other significant digits are significant ( 107 / 1.209 x 10^-7)
- a lone zero proceeding a decimal point is not significant (0.749)
- zeros between the decimal point and the first non-zero digit are not significant (0.03739)
- zeros at the end of a number are significant if they are to the right of the decimal point (0.37390)
- zeros at the end of a number may be significant if the number is written without a decimal point (100)
Calculations with Sig Figs.
multiplication or division: answer can’t have more sig figs than any of the original numbers
addition or subtraction: answer can’t have more digits to the right of the decimal point than any of the original numbers
Rounding: at the end of the calculation
Significant Figures
- digits in a number that are known with certainty plus the first uncertain digit
- more significant digits = more precise
- sig figs apply only to measurements
- exact values - unlimited number of sig figs (pi)
Dimensional Analysis
method that uses conversion factor to convert a quantity expressed in 1 unit to an equivalent quality in a different units
