3.1 SIGNIFICANT FIGURES The Concepts. Significant figures pertain to MEASUREMENTS.

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Chapter 2 – Scientific Measurement

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Presentation transcript:

3.1 SIGNIFICANT FIGURES The Concepts

Significant figures pertain to MEASUREMENTS

PRECISION VS ACCURACY PRECISION 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 precise a measurement is, the MORE LESS significant figures it has. They are DIRECTLY INVERSELY related.

Why would you ever use rulers #1 and #2, if #3 is available? ?

Think about the balances we use in class…

PrecisionCost: (grams)in dollars

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’re SO PROUD!

Does your balance need calibration?

Has the concentration of your solution changed?

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 of NUMBERS BY DEFINITION 1 foot = EXACTLY 12 inches 1 kg = EXACTLY 1000 g 1 a.m.u. = EXACTLY 1/12 th 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’T significant, because they indicate that

PART 3 THE RULES OF SIGNIFICANT FIGURES will be found in our textbook.