Chapter 2 Matter and NRG

Chapter 2Measurements and Calculations

2.1 Scientific Method

scientific method logical, flexible, problem solving approachdefine problemdevelop a questiongather information or researchredefine problem or question develop a hypothesisprediction or testable statement

experiment or test hypothesiscollect datavariables factors that can affect experimentindependent variable value or variable being manipulatedx-axis on graphdependent variable the value being measured or caused by the change in the independent variabley-axis on graphcontrol condition that remains constant thru-out experiment possibly develop a theory or a lawtheory explains what, how or whylaw statement of fact

(1) Collect data.(2) Analyze the data, looking for a trend. (If found, the trend is a "Natural Law*.")(3) Hypothesize a reason for the trend.(4) Test the hypothesis. If it fails, repeat (3) as many times as necessary.(5) If the scientific community agrees, the hypothesis is accepted as a theory (with your name on it, if you are lucky).*A Natural Law does not need an explanation. You can create a cuckoo clock driven by a falling weight without knowing anything about Newton's Theory of Gravitation.

different theories and lawsT or L - Big BangT or L - InertiaT or L - Dinosaur extinctionT or L - structure of an atomT or L - evolutionT or L - conservation of NRGT or L - Boyles press & temp directly relatedTheoryTheoryTheoryTheoryLawLawLaw2.2 Units of Measurement

qualitative descriptors describe how the object feels/looks/tastes,light, heavy, sour, sweet, shiny, dull,not very useful in science

quantitative descriptors describe the object with measurements10.5 grams, 47.85 milliliters, 1.43 grams/literuseful to compare objects to one another

fundamental units - those measurements that can be found directlylength, mass, temperature, time

derived units - measurements that can be calculated from other measurescombinations of SI unitsvolume = L x W x Hspeed = length/timedensity = mass/volumeSI units - international system of measuremetrics

Countries that still use the lame English measures

jerseylicious video(link)

fundamental SI unitslength meter(m) ~ 1 yardmass kilogram(kg)~ 2.2 lbstime second(s)temperature kelvin(1 K= 1oC)amount of a substance mole(mol) 1 mole = 6.023 x 1023electrical current ampereluminosity candela

measuring fractions w/ OCC

other metric unitsvolume amount of space occupiedm3 = SI derived unitliter(L) ~ 1 quart1 cm3= 1 mLdensity ratio of mass to volumekg/m3 = SI derived unitg/mL, g/Lwater has density of 1 g/mLenergy joules, calorie4.19 joules = 1 calorie

metrics/SI system uses base 10prefixes following base 10giga G= 1 000 000 000 base unitsmega M= 1 000 000 base unitskilo k= 1 000 base unitshecto h= 100 base unitsdeka dk= 10 base unitsbase unit= 1 base unitdeci d= 0.1 base unitscenti c= 0.01 base unitsmilli m= 0.001 base unitsmicro - = 0.000 001 base unitsnano n= 0.000 000 001 base unitsking henry died __by__ drinking chocolate milk

convert the following 1 meter = _______ cm

10 kg = ________ g

175.5 mL = ___________ L

27.75 mg = _____________ kg

10010 0000.175 50.000 027 75

scientific notationa shorthand method of writing very large or very small numbers1 000 000 = 1 x 106602 200 000 000 000 000 000 000 = 6.022 x 10230.000 001 = 1 x 10-60.000 000 004 5 = 4.5 x 10-9 4 270 000 =0.000 000 340 =

4.27 x 106 3.40 x 10-7 Practical use of SI units and scientific notation(link)2.3 Using Scientific Measurements

accuracy proximity of a measurement to an accepted valueexample measured density of lead to the accepted density of lead

accepted values found in CRC, online, textbook,calculate accuracy = % error%error = (exp. value accepted value)/accepted value x 100

precision the proximity of several(3 or more) measurements to one anotherno accepted valueexample - % of Cl in dive tank at Mandan Poolexample - temp of Missouri River water on Jan. 3rd example:

calculate precision = % deviationcalc. mean of all trials(3 trials minimum)calc. absolute deviationabs. dev. = (trial mean)calc. mean of abs. dev.calc. % deviation% deviation = mean abs. dev./mean of all trialssignificant figuressig figs, sig digs,a uniform method of representing accurate measurements and answers represents the exact measure + 1 digit as an estimateexample

Determining Sig Figs - see rules on page 47, table 5

exact numbers have an infinite # of SFsexample 100 cm = 1 mexample 60 s = 1 min

Pacific OceanAtlantic OceanPresentAbsent

how many SFs in the following #s????30450 = ________32.0500 = _________2.00 = __________0.000310 = _________3.010 x 10-4 = _________5.000 x 1011 = _________500 000 000 000 = ________4633441Calculations using SFsmultiplication and division w/ SFsthe answer contains same number of SFs as the least that was mult. or div. 48.2x 9.233445.0306

2371005421103 sf4 sf3 sf= 0.43736511 4 sf 5 sf 4 sf445= 0.4374

calc. using SFs (cont.)adding and subtracting w/ SFsthe answer of any add. or sub. will have the last SF in the highest place value of the last SF which has been added or subtracted

235.320+ 12.4247.720

65.73- 3.2654162.46459last sf is in the thousandths place valuelast sf is in the tenths place valuelast sf is in the tenths place valuelast sf is in the hundredths place valuelast sf is in the hundred thousandths place valuelast sf is in the hundredths place value247.762.46dimensional analysisunit cancellation, label division,problem solving technique that uses fractions and labels to determine the steps to solveconversion factors

ENERGYenergy(NRG) capacity to do workmoving an objectcreating new compoundcreating light or electricityNRG change always accompanies physical or chemical changewhen ice melts, NRG is added to the icewhen water freezes, NRG is given up by the waterwhen vinegar is added to baking soda, NRG is released when bubbles of gas form

law of conservation of NRGNRG can not be created or destroyedchanged/transfered from one form to anotherexample gasoline, wind turbines,

NRG transfer involvessystem the substance or matter being observedsurrounding everything else around the systemexample glass of cold water = systemsurrounding = air, hand, countertop,exothermic a process(chemical or physical) in which NRG is released from the system to the surroundingresulting substance has less NRG than starting substancefeels hot you are absorbing some of the NRG being releasedbon fire, hand warmer, your body in a cold lake

endothermic a process(chemical or physical) in which NRG is absorbed by the system from the surroundingresulting substance has more NRG than starting substancefeels cold to touchyou are losing NRG to the system/substancechunk of ice in your hand, photosynthesis

heat = NRG NRG that is transferred between objects of different temperaturerelated to temperaturemeasured in joules(J)calorie amount of NRG needed to raise the temp of 1 gram of water by 1oC1 cal = 4.19 Jtemperature measure of the average kinetic NRG of a systemmeasures how much the particles are movingkinetic NRG NRG of motionrolling carflowing watermotion of particlespotiential NRG NRG of positiona car on top of a hillwater behind a damchemical NRG stored in bondstemperature = the avg. KE of a system o C , K, (o F) Temperature conversions:conversion from Co to Fo Fo = ((Co +40)x 9/5)-40

conversion from Fo to Co Co = ((Fo +40)x 5/9)-40

conversion from Co to KK = Co + 273

conversion from K to Co Co = K - 273