Estimates, Averages, and Sig Figs October 6, 2015 (2.2 in your books)

Meme Moment

Scientist of the Day

Jonas Salk Invented polio vaccine people used to get polio in the US each year o 1/3 of them ended up partially paralyzed o Iron lung Funded by March of Dimes Refused to patent invention Polio now gone in all but 3 countries

Percent Error

Range Range: the spread of data Math: biggest # - smallest # In high school/college you might have a different definition, but use this one for now. 8 th grade

Anomalous Data Sometimes you make a data set and one number looks really weird This is anomalous data Anomalous data is useful – it can tell you if your equipment isn’t working right, or maybe you forgot to control for a variable If your averages and percent error are strange, look for anomalous data

Significant Figures Significant figures = sig figs How scientists tell each other how precise a number is. Sig figs are made up of all the measured values (increments) + one that we estimate o Like how we measured volume in a beaker, then estimated in between the smallest marks From now on, all answers must be in sig figs ! Sig the Fig

Zeroes in Sig Figs A number that isn’t zero always counts Zeroes in the middle always count Zeroes at the start don’t count Zeroes at the end don’t count unless there’s a decimal NumberSignificant Parts# Sig Figs

More Sig Figs! NumberSignificant Parts# Sig Figs

Adding/Subtracting Sig Figs Use the smallest number of decimal places (or tens, hundreds, thousands, etc) Round to that number!

Multiplying/Dividing Sig Figs Use the smallest number of sig figs Round to that number!

More Stuff If you are using a conversion factor like “1000 g/ 1 kg” you have unlimited sig figs If you are using a counting number like “2 people,” you have unlimited sig figs

Homework Worksheet! It’s double-sided and due Friday. All answers must be in sig figs. Worksheet covers 2.1 and 2.2.

Questions Any questions about the slides? Any new questions?