Scientific Conventions and Mathematical Procedures Accuracy, precision, significant figures, scientific notation, conversions, dimensional analysis

FRIDAY we talked about – Accuracy and Precision Closeness to the true value Requires a tool that is calibrated and used properly Repeatable measurements How close do the measurements agree with each other

Added and subtracted #s column “mass of Water” Multiply and divide Density

Significant digits Significant digits are used to convey information about the precision of measurement. When using measured quantities in calculations the following rules should be applied to express significant figures correctly. In addition or subtraction, express the answer with the same number of decimal places as the quantity having the fewest decimal places. 14.25g + 12.25g =26.50g 15.23g – 10.1g = 5.1g In multiplication or division calculations express the answer with the same number of significant figures as the quantity having the fewest number of significant figures 20.01 x 16.15 = 323.1 13 cm x 5.10 cm= 66 cm2

Significant Digits All non-zero digits are significant All “captured zeros” are significant In numbers that DO NOT have a decimal final zeros are not significant In numbers that have a decimal Leading zeros are not significant Final zeros are significant Special Rules All digits are significant in correct scientific notation A decimal can be added to make digits significant

Scientific Notation using the powers of ten to express very large and very small numbers To add and subtract scientific notation you must convert the numbers to the same exponent To multiply you must add the exponents To divide you must subtract the exponents

TO AVOID ERRORS LEARN TO USE THE CALCULATOR- TODAY There is a button that says EE, it will save you lots of time, confusion and give us time to focus on higher level chemistry concepts