chem chapter 3

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experimental value

the value measure in the lab

cubic centimeter cm^3=1 mL; cube of sugar =1 cm^3

...

1 atom of gold

.000000000000000000000327 grams

kilometer (km)

1 km = 10^3; length of a bout 5 city blocks

3 temperature scales

1) celcius- based on the freezing point of water (0 degrees celcius) boiling point of water (100 degrees celcuis) conversion = degrees celcius = (degrees farenheit - 32) / 1.8

rules for sig figs in measurement

1) every non-zero digit in a measurement is significant i.e. 24.7 L, .31286 kg, 952 173 mm 2) zeroes between non-zero digits are significant i.e. 7003-4, 40.792-5 3) leftmost zeroes in front of a non zero digit are NOT significant (they are only place holders); when reading left to right, nothing is significant until the first non-zero digit i.e.-.00632-3 0.42-2 4) zeroes at the end of a number that are after a decimal point are significant i.e. 43.00-4 1.010- 4 5) zeroes at the rightmost end of a number but before an understood decimal are NOT significant i.e. 300 km - 1 70 000-1 275 410-5 6) there are 2 situations when numbers have an unlimited/infinite number of sig figs -1) counting numbers of items i.e. 24 crayons in a box, 16 people in the room -2) conversion factors i.e. 60 mins/1 hour=1 hour/60 mins

si temp

Kelvin

decimeter (dm)

10^1 dm=1 m; diameter of a large orange

centimeter (cm)

10^2=1 m; diameter of a shirt button

millimeter (mm)

10^3 mm=1m ; thickness of a dime

millilter mL

10^3mL=1L; 10 drops of water= 1 mL

microliter (mL)

10^6 ML=1 L; crystal of table salt = 1ML

macrometer (Mm)

10^6 Mm=1 m'diameter of a bacterial cell

nanometer (nm)

10^9 nm=1m thickness of RNA molecules

1 atom of gold

3.27 x 10^-23

1 gram of hydrogen (scientific notation)

6.02 x 10^23

1 gram of hydrogen

602000000000000000000000 atoms

sig figs

all of the digits known in a measurement plus one estimated digit

if converting a prefix to a prefix

always go through the base

si electric current

ampere

meter (m)

base unit; height of doorkob from the floor

LITER

base unit; quart of milk

Kelvins (K)

based on the concept of absolute zero (0 Kelvin, all molecular movement has stopped) conversion: K = degrees celcius +273 * note a change of 1 degree celcius is equivalent to a change of 1 K

farenheit scale

based on the freezing point of water (32 degrees f) and boiling point of water (212 degrees f) conversion: farenheit= 1.8 degrees celcius + 32

si luminous intensity

candela

energy

capacity to do work or produce heat, called a joule (J), common non-SI unit is calorie (cal) 1 cal is the quantity of heat that riases the temperature of one gram of pure water by 1 degrees celcius 1 Joule=.2390 cal 1 cal = 4.184 J

m temperature

celcius

accepted value

correct value for the measurements based on reliable references

division in scientific notation

divide the coeffecients and subtract the exponent in the denominator from the exponent in the numerator

equation for percent error

divide the error by the accepted value and multiply by 100

decimeter

equal to 10 cm, so 1L = 1 dm^3, 1000 mL = 1L and 1000 cm^3 = 1L so 1 mL=1 cm^3

equation to calculate error

error = experimental value-accepted value (EV-AV)

what are measurements fundamentalt to?

experimental science

addition and subtraction

exponents have to be the same

sig figs w/ multiplication and division

for calculators involving multiplication and divison the answer to the same number of sig figs as the measurement with the least number of sig figs

how does heat travel

from a warmer body of matter to a colder body of matter

positive powers of 10

go with base unit

negative power of 10

goes with prefix

m mass

gram

scientific notation

helps us write numbers faster and easier, has 2 parts- coefficient and power

accuracy

how close a measurement is to the actual or true value, to evaluate the accuracy of a measurement, it must be compared to the actual value

precision

how close a series of measurements are to each other, irrespective of the actual value, to evaluate precision of a measurement, you must compare the values of 2 or more of these repeated measurements

sig figs in calculators

in general a calculated answer cannot be more precise than the least precise measurement from which it was calculated i.e. a room was measured and reported to have the dimensions 7.7 meters (2 sig figs) by 5.4 meters (2 sf), calc area = 7.7m x 5.4m=41.6 m^2

negative integer

indicates number in standard form is <1

positive integer

indicates the number in standard from is >1

error

individual measurements can be accurate or inaccurate

what type of property is density

intensive

SI units

international system of units, a revised version of the metric system, 7 SI base units, 5 of which are most chommonly used by chemists (all other units can be derived from these), all measured quantities can be reported in SI units although sometimes it is more convenient or practical to use non-SI we use both, chemists treat Liter (L) as an SI even though its not, "unofficial

si mass

kilogram

see notes for metric prefixes and SI units

l.lsdjfoaids

volume m

liters

Mass

mass is not weight, weight is a force that measures the pull on a given mass by gravity (mass is the measure of the amount of matter), kilogram (kg) 1 kg=10^3 g; small textbook gram (g): metric base; dollar bill milligram (mg): 10^3 mg=1g; 10 grains of salt microgram (Mg) 10^6Mg= 1 g; particle of baking powder

m length

meter

si length

meter

si amount of substance

mole

liter

more convenient unit of volume and is equal to the amoundt of space by a cube that measure 1000 cm^3 = 1 L

multiplication in scientific notation

multiphy numbers in scientific notation, multiply the coefficients and add the exponents i.e. (3x10^4) x (2x10^2) = (3x2) x 10^4+2 = 6x10^6

power

multiply by 10 raised to a power where the power is an integer

coefficient

number between 1 and 10

measurements

quantities that include both a number and a unit, fundamental to experimental science, it is important to make measurements as well as decide they are correct and reasonable, encounter numbers that are very large or very small

si time

seconds

sig figs with addition and subtraction

should be rounded to the same number of decimal digits (NOT total digits) as the measurement with the least number of decimal digits ex. 31.5m+862.391m+100.26=994.151m=994.2, 9.942x10^2m

percent error

should be within .1 or 10% to be accurate, do not take the absolute value (this is different than the book)

metric system

simple and easy to use, based on multiples of 10, making it easy to convert between units

temperature scales

temperature is the measure of how hot or cold a body of matter is, heat only travels from a warmer body of matter to a colder body of matter, most substances expand when heated and contract when cooled, one important exception is water- water expands when it is freezes (so ice is less dense than liquid water which is why ice floats)

error

the difference between the experimental and accepted values

rounding

to round a number, one must first decide how many sig figs the answer should have; then look only at the digit to the right of the last sig fig, if the digit is <5, drop it and if the digit is > or = to 5, then you round up i.e. 87.073=87.1 m=8.71 x 10^1m

volume

v=lxwxh, SI unit is amount of space occupied by a cube that measures 1m^3

steps for converting between units its the metric system

we will use

steps for converting between units in the metric system

we will use FLM and no negative exponents during the problem (only at the end, if necessary, for the answer) 1) start with what you are given 2) if you are given a base unit or converting to a base unit the prpocess will be only one step, the power of 10 will go with the small unit or the lower one of the chart (see examples in good notes)


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