The Uses of Numbers

Chemistry is a quantitative science. *It is all about the quantity* NUMBERS!!!! *It is all about the quantity* NUMBERS!!!!

Qualitative Data can also be identified. *This is quality* NO NUMBERS INVOLVED! *This is quality* NO NUMBERS INVOLVED!

Le Systeme International d’Unites (SI) - The Metric System A modernized form of the metric system adopted in 1960 and is used by scientists in every nation This system has a small number of base units from which all other necessary units are derived. A modernized form of the metric system adopted in 1960 and is used by scientists in every nation This system has a small number of base units from which all other necessary units are derived.

METRIC UNITS QUANTITYUNITABBREV. MASSkilogramkg LENGTHmeterm TIMEseconds TEMPERATURE KelvinK AMOUNTmoleMol

What about really little, or really big stuff? these units are useful, but many times we wish to measure things that are either much larger or much smaller

To handle this, we use prefixes PREFIX ABBR.MEANING EXAMPLE MEGAM MEGABYTE = BYTES KILOk KILOGRAM = GRAMS DECId DECILITER=0.1 L CENTIc CENTIMETER = 0.01 M MILLIm MILLIMETER= M MICRO  MICROGRAM = G NANOn NANOLITER = PICOp PICOMETER = M

SO WHICH UNIT WOULD YOU USE? The length of an eyelash mm The height of a flagpole m The length of a strand of spaghetti cm The distance from Dallas to Austin km The length of an eyelash mm The height of a flagpole m The length of a strand of spaghetti cm The distance from Dallas to Austin km

The reliability of a measurement has two components: PRECISION – How close together were the numbers? How consistent were the numbers? ACCURACY-How well measurements agree with the accepted value PRECISION – How close together were the numbers? How consistent were the numbers? ACCURACY-How well measurements agree with the accepted value

Precision

accuracy

Precision and accuracy

Data Table: Boiling Point of Water ReadingThermometer 1Thermometer 2Thermometer 3Thermometer °C97.5°C98.3°C97.5°C °C102.3°C98.5°C99.7°C °C 99.7°C 98.4°C96.2°C °C100.9°C98.7°C94.4°C Average °C 100.1°C 98.5°C 97.0°C Range Accurate? Precise?

Scientific Notation In chemistry, we deal with very large and very small numbers For example, there are approximately 602,000,000,000,000,000,000,000 molecules of water in one mouthful! In chemistry, we deal with very large and very small numbers For example, there are approximately 602,000,000,000,000,000,000,000 molecules of water in one mouthful!

one electron weighs about kilograms!

Try these! Change 5.3 x to standard notation. Change 6.03 x 10 7 to standard notation. Change 5.3 x to standard notation. Change 6.03 x 10 7 to standard notation.

So, 602,000,000,000,000,000,000,000 would be written as 6.02 X because there are 23 zeros to the left of the decimal would be written as 1.19 x because there are 32 spaces to the right of the decimal point So, 602,000,000,000,000,000,000,000 would be written as 6.02 X because there are 23 zeros to the left of the decimal would be written as 1.19 x because there are 32 spaces to the right of the decimal point

Try these! Change to scientific notation Change to standard notation Change to scientific notation Change to standard notation

Significant Figure Rules!!! 1. All digits 1-9 are siignificant 2. Zeros between significant digits are always significant 3. Trailing zeros in a number are significant only if the number contains a decimal point. 4. Zeros in the beginning of a number whose only function is to place the decimal point are not significant 5. Zeros following a decimal significant figure are significant. 1. All digits 1-9 are siignificant 2. Zeros between significant digits are always significant 3. Trailing zeros in a number are significant only if the number contains a decimal point. 4. Zeros in the beginning of a number whose only function is to place the decimal point are not significant 5. Zeros following a decimal significant figure are significant.

Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

00100 Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

5009 Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

9000 Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

3.60 Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere

123,680 Numbers 1-9 are significant Leading zeroes do not count Numbers with a decimal become significant only if the number follows a number 1-9 Zeroes that are sandwiched in by significant numbers are significant Lagging zeroes do not count unless there is a decimal somewhere