Two Key Concepts
Matter is made of various kinds of atoms
Chemical changes occur when atoms
1.2 Scientific Process
Ex. Pb(NO3)2 + NaI
Hypothesis- possible explanation for observation
Model/Theory- tested hypothesis; gives
explanation to natural phenomenon.
Law- Observed behavior; summary of what
Law of conservation of mass
1.5 Rules for Significant Figures
Non zero integers always count
Zeros – there are three classes
Leading Zeros – these do not count
Captive Zeros – these always count
Trailing Zeros – They are only significant if
the number has a decimal point.
These do not limit the number of
Rules for Mathematical
For multiplication and division the number
of significant figures is the same as the
least precise number
For addition and subtraction the result has
the same number of decimal places as
the least precise measurement.
Rules for Rounding
In a series of calculations carry the extra
digits through to the final result, then
If the digit is to be removed is less that 5
the preceding digit remains the same.
If the digit is equal to or greater than 5 the
preceding digit is increased by one.
Round the following to 3
1.6 Dimensional Analysis
Line the various numbers up with their
units and cancel out units. If the unit of
the final answer is correct then you
mathematical answer should be correct.