# Important Things to Remember about Logs (or else...)

Logs make it easier to compare measurements that vary by many orders of magnitude.

Positive logs mean big numbers – bigger than one.
To find the approximate log, simply count the number of digits AFTER the first digit.

Negative logs mean small numbers – between zero and one.
To find the approximate log, count the decimal point plus number of zero's UNTIL the first non-zero digit.

Logs are the same as the exponent you would need to put on a "10" in order to get your original measurement: in other words, The Log is the Power.

Going UP BY ONE on a log scale is always the same as multiplying by 10. Going DOWN BY ONE on a log scale is always the same as dividing by 10.

You can recover the original measurement by raising 10 to the log ( or "10^___ =" on Google).

The pH scale is based on the NEGATIVE log of concentration of H+ ions.

The Richter scale is based on the log of energy released.

If you want a printer-friendly version of this module, you can find it here in a Microsoft Word document. This printer-friendly version should be used only to review, as it does not contain any of the interactive material, and only a skeletal version of problems solved in the module.