SIGNIFICANT FIGURES AN EASY METHOD TO AVOID PRODUCING MISLEADING RESULTS

IT’S EASY! IT’S FAST! Two Rules are used: One for Adding & Subtracting One for Multiplying & Dividing

When adding or subtracting Note accuracy of measurements (nearest.1?.01?.001?) Answer can be no more accurate than the LEAST accurate number that was used to calculate it.

For Example: 5.50 grams grams grams

OR ml ml ml --> 2.4 ml

When multiplying or dividing You must COUNT significant figures The answer can have only AS MANY significant figures as the LEAST of the numbers used to get it

Here is a one sentence rule for counting sig figs: All digits ARE significant except Zeros preceding a decimal fraction and Zeros at the end of a number containing NO decimal point

For Example:.0045 has 2 significant figures but has 5 significant figures

AND has 4 signifcant figures while has 6 sig figs and.0005 has only 1 sig fig

Numbers with no decimal are ambiguous... Does 5000 ml mean exactly 5000? Maybe.... Maybe Not! So 5000, 500, 50, and 5 are all assumed to have 1 significant figure If a writer means exactly 5000, he/she must write or x 10 3

How many sig figs in each #?

Now let’s do some math..... (round answers to correct sig figs!) g g answer: 6.55 g Did you need to count sig figs? NO!

Try this one ml ml answer: 4.80 ml (one might say.0015 is insignificant COMPARED TO 4.80)

Now try these g / 5.0 ml answer: 1.0 g/ml Did you have to count sig figs? YES!

Here’s a tougher one C/s x 60 s/min x 60 min/hr = answer: C/hr --> C/hr Note: standard conversion factors never limit significant figures-- instruments and equipment do.

THAT’S ALL THERE IS TO IT! Use least accurate measurement when adding and subtracting Count sig figs when multiplying and dividing