Chapter 2Sig figs and math

Be sure to write all notes from class and problems -

Metric SystemKing Henry Died –drinking choc milk

Kilo-k— 1000x Hecta-h- 100x Deka- da- 10X Deci-d- 1/10 Centi – c- 1/100 Milli- m - 1/1000 Micro- u - 1/1000000

International System of Units SI is the abbreviation Based on standards that never change

LengthUses the meterSymbol mBased on the distance that light travels in a vacuum during a timed interval

*2.54 cm = inch 1.6 km = mile

Mass Uses kilogram (we will use grams) Symbol kg Based on a Pt-Ir cylinder 2.2 lb = kg mass=amount of matter Weight- gravitation pull on an object

Time Uses second Abbreviation s ( or sec) Based on the radiation emitted by a Cs-

133 sample 60 s = min 60 min= hour

Derived units A combination of base units Density= mass / volume Volume = length x width x height cm3 = mL Water only density is equal to 1.00

g/mL

Bouyant- float- density is less than 1.0g/ml

Sink- density is greater than 1.0g/mL

Meniscus- curve of the liquid– read the bottom for water

Temperature and Heat Heat is the total Kinetic energy and is

dependent upon mass- Measured in Joules

Temperature is the average Kinetic energy- uses a temperature scale

Temperature Measure in celcius Kelvin- based on absolute zero (particles

are motionless) Convert to Kelvin

C + 273 = kelvinK- 273 = C

Energy Energy is measured in Joules 4.184 Joules = calorie 1000 calories = 1 Calorie Calorie is the unit used in food

descriptions

Specific Heat Specific Heat is the heat needed to raise

1 gram of a substance 1 degree C Formula: C- Specific Heat Capacity

m- mass t – change in temperature

Accuracy and Precision Precision- value repeats Accuracy- closeness to accepted value

Percent error= Exp- theoretical x 100

Theoretical

Accuracy and PrecisionProblems The product had a mass of .125g. The

known value was .130g. What is the %error? (must write formula)

Significant Figures sig figs All certain digits and 1 estimated (Under the files on my website are some

rules if needed)

Significant Figures Pacific/Atlantic Rule

Decimal point PRESENT? Start from the PACIFIC!

Begin counting on the left hand (Pacific) side of the number. Move toward the right and start with the first non zero digit.

306.4000 = 7 significant figures

1200. = 4 significant figures

0.00004 = 1 significant figure

0.000040 = 2 significant figures

Decimal point ABSENT? Start from the ATLANTIC!

Begin counting on the right hand (Atlantic) side of the number. Move toward the left and start with the first non zero digit.

1200 = 2 significant figures

1207 = 4 significant figures

Pacific Atlantic

Conversion factors are NOT considered when determining the number of sig figs

Multiply or Divide The answer should contain the lowest

number of sig figs in the problem

Add or Sub The final digit is in the same place as

the left most sig fig

Scientific notation We reviewed this in class- come by if

you need help

Factor Label Conversion factors are used to change from one

unit to another. Ex- dozen=12

foot=12 inches2 pints = quart2.54 cm = inch2.2 pounds=kilogram1.6 Km = mile5280ft=mile

mole Mole is a counting unit used in

chemistry Mole = 6.02 x 1023 atoms, particlesA mole allows for comparisons to be made between elements or compounds.