Significant Figures: Precision and Accuracy in Measurement in a dartboardPublic Domainview termsPublic Domain PeterPan23PeterPan iki/File%3AGlass_graduated_cy linders-set.jpgBy Lilly_M [GFDL ( html) or CC-BY-SA ( nses/by-sa/3.0)], via Wikimedia Commons g_scale#mediaviewer/File:Balance_Ker n.jpgBalance KernPublic DomainPublic Domain KareljKarelj - Own work

Target Practice You have 5 arrows. Mime shooting the bow. Be sure to make a “thwack” sound each time you shoot. Good luck!

Simple Bow

gBy Caiguanhao [GFDL ( or CC-BY-SA ( via Wikimedia Commons

Was the shooter accurate? Was the shooter precise? Why or why not?

Compound Bow

gBy Caiguanhao [GFDL ( or CC-BY-SA ( via Wikimedia Commons

Was the shooter accurate? Was the shooter precise? Why or why not?

Cross Bow

gBy Caiguanhao [GFDL ( or CC-BY-SA ( via Wikimedia Commons

Was the shooter accurate? Was the shooter precise? Why or why not?

Which is Accurate? Which is Precise? Which are neither accurate nor precise? is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License,GNU Free Documentation License

So, what do precision and accuracy mean in your labs? Precision is how close your lab measurements are to each other Accuracy is how close your measurements are to the correct value. ns.wikimedia.org/wiki/File %3A25_Met er_Precision _and_50_M eter_Pistol_ Target.svgB y Caiguanhao [GFDL ( gnu.org/copy left/fdl.html) or CC-BY- SA ( ecommons.o rg/licenses/b y-sa/3.0)], via Wikimedia Commons

How do we express accuracy in measurement? We record the measurement according to the accuracy of the equipment used plus one estimated digit. Pleple2000 (Own work) [GFDL ( or CC-BY-SA ( via Wikimedia Commons ance_electronique%281%29.JPGBalance electronique(1)Domaine publicDomaine public

Remember: Estimate one digit between the lines. What is the correct reading for the cylinder? Meniscus Answer: 100. mL Lucasbosch (Own work) [CC-BY-SA-3.0 ( via Wikimedia Commons Read the bottom of the meniscus.

Least accurate Most accurate 665 mL mL s#mediaviewer/File:Meniscus.jpgMe niscusCC BY-SA 3.0CC BY-SA 3.0 PRHaneyPRHaney - Own work uated_cylinder-1000ml.jpgBy Lilly_M [GFDL ( or CC-BY-SA ( sa/3.0)], via Wikimedia Commons Read the graduated cylinders correctly. Which cylinder is the

Which balance is more accurate? Estimated digit e:Analytical_balance_mettler_ae-260.jpgAnalytical balance mettler ae-260Public Domainview termsPublic Domain Stan Zurek (Own work) [GFDL ( CC-BY-SA-3.0 ( or CC-BY-SA ( via Wikimedia Commons

Rules for Significant Figures

Rule 1: Nonzeros are always signficant. Examples: ,526 3 SF 2 SF 5 SF

Zeros are the problem!! There are 3 kinds of zeros: –CAPTURED: in the middle –PRECEDING: on the left –TRAILING: on the right

Rule 2: CAPTURED zeros are ALWAYS significant. Examples: , SF 6 SF 4 SF

Rule 3: PRECEDING zeros are NEVER significant. Examples: SF 6 SF 4 SF

Rule 4: TRAILING zeros are significant WITH A DECIMAL present. Examples: SF 3 SF 4 SF 8 SF Challenge: Write one hundred in 2 SF.

Significant Figures in Calculations 84_Plus_series#mediaviewer/File:TI- 84_Plus_Silver_Edition.JPGTI-84 Plus Silver EditionPublic DomainPublic Domain

Multiplying and Dividing Rule 5: When multiplying or dividing the answer will have the same SF as the least accurate measurement. Example: m = g V = 10.1 mL D = m/V = 9.567g/10.1 mL = = g/mL g/mL Note the use of Given, Formula, Substitute, Solve 3 SF m/royalty-free-stock- photos-icon-multiply- divide-image

Rule 6: Counted, known, and accepted values DO NOT affect significant figures. Example: (20 students)(68.18 kg avg. mass) = kg Round answer to 4 sig figs. = 1364 Kg Least accurate measurement Counted value has no affect

Adding and Subtracting Rule 7: When adding and subtracting, the answer is rounded to most accurate decimal place shared by all the measurements. Example:209.7cm 8.004cm cm cm Tenths column is the most accurate decimal place shared by all the measurements, so round to tenths. Final answer: cm

…for now… _The_End_(67).pngBy Dorothy Sherrill (Internet Archive) [Public domain or Public domain], via Wikimedia Commons