3.1

SIGNIFICANT

FIGURES The Concepts

Significant figures pertain toMEASUREMENTS

PRECISION VS ACCURACYPRECISION IS _____________________a set of measurements are to each other

ACCURACY IS _____________________a measurement is to the

_________________________________ of what is being measured

SIGNIFICANT FIGURES are….All of the digits (numbers) in a

_______________________ that can be

known ___________________ plus one

______________________ digit.

Your very first apartment….

Rulers #1 and #2 – Line A

Ruler #3 – Line A

PART 2 CONCEPTS OF SIGNIFICANT FIGURES

The number of significant figures that a measurement has is determined by

________________________________

________________________________

The MORE LESS precisea measurement is, the

MORE LESS significant figures it has.

They are DIRECTLY INVERSELYrelated.

Why would you ever use rulers #1 and #2,

if #3 is available??

Think about the balances we use in class…

Precision Cost:(grams) in dollars

0.10.010.0010.0001

What you buy depends on what you need it for……..

Factors to consider when buying a measuring tool:

How much ___________________ do you need?

How much can you _________________________?

Which is ____________________________ to use?

Equipment with greater precision requires

more _______________________________ to use

and more _________________________________

Another example: beakers vs volumetric flasks

If you use a costly measuring device, that gets many significant

figures, your measurement is more

PRECISE.Is it also more

ACCURATE?

You worked SO HARD, and you’reSO PROUD!

Does your balance need calibration?

Has the concentrationof yoursolutionchanged?

A type of measurement you’ll soon be doing in the lab…What is a meniscus?

Another concept……

EXACT NUMBERS are…

numbers by _________________ &

numbers by ___________________

They have ____________________significant figures

Some examples ofNUMBERS BY DEFINITION

1 foot = EXACTLY 12 inches

1 kg = EXACTLY 1000 g

1 a.m.u. = EXACTLY 1/12th the mass of 1 atom of carbon-12

FINAL CONCEPT:

ZEROES TO THE RIGHT OF A NUMBER

(where there is a decimal point)

Ruler #3 – Line B

Ruler #3 – Line C

Zeroes to the right of a number(where there is a decimal point)

ARE AREN’Tsignificant, because they indicate that

PART 3 THE RULES OF SIGNIFICANT FIGURES

will be found in our textbook.