4 Summary
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Review Module 1 Material
Scientific Measurement
Accuracy: 
How close a measured value is to the accepted or real value. 
Precision: 
The degree of reproducibility of a measured quantity; how close a series of measurements of the same quantity are to one other. 
Volume: 
Volume is a measure of space. It is a unit of length raised to the third power. The SI unit of length is the meter. One meter cubed is equivalent to 1000 L. Litres, which are a convenient unit for scientific measurements, are a more common measurement unit than meters cubed.

Density: 
A ratio of mass (m) to volume (V) of a substance. 
SI Base Units
Click on the following units of measurement to reveal their definition.
Note: Precise definitions of the SI units are not necessary to memorize. Rather, the relationships between the units and how to use them are the important parts to know.
SI Prefixes: Units of Measure for All Sizes
Multipliers that change unit values by multiples of ten.
Presenting Chemical Data
Significant Figures
An accepted method for preserving the precision of a measurement when recording data or doing calculations.
1.  2.  3.  4. 
Nonzero digits are significant.  Exact numbers are significant.  Contained zeros are significant.  Leading zeros are not significant. 
5.  
Trailing zeros have significance as follows:  
a.  b.  c. 
After a decimal point, significant  After a nonzero number and before a decimal point, significant  After a nonzero number that in not a decimal number, generally a place holder 
For an even more detailed breakdown on significant figures click the link below to view.
Scientific Notation
A notation for expressing large and small numbers as a small decimal between one and ten multiplied by a power of ten.
How to write using scientific notation:
1. 
2. 
2a. 
2a. 
Move the decimal point to the left or right to reach a decimal number between one and ten.  Write the number obtained in step 1 multiplied by 10 raised to the number of places the decimal point was moved. 
If the decimal is moved to the left, the power is positive. Example: 
If the decimal is moved to the right, the power is negative. Example: 
Chemical Problem Solving Strategies
Unit Analysis and Problem Solving
A ‘bookkeeping’ method for units in a calculation 
Over all method of “unit analysis”: 
Indicates errors in a multistep calculation
Provides the units for the final answer 
1) Write the units with every number you include in a series of calculations 2) String your calculations together as a series of multiplications or divisions before doing any math 3) Cancel your units to see the calculation evolve 
Calculations: Converting from One Unit to Another 

Unit analysis: 
Conversion factor: 
A method that uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit. 
States the relationship between two different units. 
original quantity x conversion factor = equivalent quantity
For example converting between length units
Given that 1 meter = 39.37 inches
Conversion factors or
The same relationship, just invert as necessary to give you the units you need!
Problem Solving Examples
How many moles of oxygen atoms are there in a 10 mL volume of water?
What is being asked? 
What data is provided? 
What do I need to know? 
How do I need to state the answer? 
Given a volume can you calculate a number of atoms?  Data: 10 mL of water  Need to know: water is , density of water, molecular weight of water  Answer in moles of oxygen O 
Convert volume of water to moles of oxygen:
Calculation is: Volume of mass of mols of mols of
= There are 0.55 moles of oxygen atoms.
Always Check Units!