Unit 3 Measurements & Calculations

Scientific Notation: Used to write very large or very small numbers Expressed as the product of 2 factors Mantissa: Express the significant digits as a number between 1 and 10, but not 10. Power of 10

Examples of use The mass of one proton is x g or g The number of copper atoms in one mole of copper is 6.02 x atoms or 602,000,000,000,000,000,000,000 atoms

532 = 20,120 = = = 5.32 x x x x 10 -3

Uncertainty in Measurements When making measurements, record all the certain numbers plus the first uncertain number.

50 mL beaker 25 mL graduated cylinder 10 mL volumetric pipet

Significant Digits are all digits which are certain, plus one uncertain digit. 0.3 zero for cosmetic is NOT significant 250. or.0025 zero to locate the decimal is NOT significant 102 or zero between non-zero numbers is significant zero to the right of decimal is significant

How many significant digits? 7.5 x ,

Multiple or division: answer has same number of significant figures as least precise measurement used in calculation Addition or subtraction: answer has same number of decimal places as least precise measurement used in calculation In a series of calculation, carry the extra digits through to the final result, then round!

Metric System: System international Measurement system based on 10. Length: meter The distance light travels in a vacuum in 1 / 299,792,458 s Volume: liter A cube that is 10 cm per side. 1 cm 3 = 1 mL Mass: kilogram 1 gram is the mass of 1 mL of H 2 O at 4 o C Time: second Temperature: Celsius or Kelvin

Metric Prefixes You need to know these and how to convert between them!

Dimensional Analysis Process used to convert from one unit of measurement to another unit of measurement. Multiply by a fraction equal to 1, which will eliminate one unit and substitute another unit. Convert 581 cm to m 581 cm 1 x 1 m 100 cm =5.81 m

Precision The reproducibility in measurements. Coming up with similar results again and again. Accuracy The closeness of measurements to the accepted true value.

Temperature Conversions O C = K O C = 5 / 9 ( o F – 32 ) O F = 9 / 5 o C + 32

Density = mass / volume ( grams / mL ) Hydrogen = g / mL Maplewood = 0.7 Glass = 2.6 Gold = 19.3 Diamond = 3.5 Osmium = 22.5 Silver = 10.5 Ice H 2 O = 0.9 Lead = 11.4Liquid H 2 O = 1.0 Mercury = 13.6

A crown supposedly made of pure gold has a mass of 1,650 g, and a volume of 180 mL. What is the density? Is it pure gold? Density of gold = 19.3 g / mL

Density = mass / volume (units of g / mL or g / cm 3 ) Example: A block of wood has a mass of 2.52 Kg. What is the density of the wood? 51 mm 6.2 cm 1.08 m

Review 1. a) 2,560 mL b).0936 Kg c).7139 m g / mL 2. a)1.1 x Volume = cm 3 b)4.31 x density = 1.04 g / cm 3 3. See notes on drawings No, it will not float! 4. a) 22 o C b) 288 K c) 20 o C