measurement & atomic theory · 2019-09-03 · idea of the atom around 430 b.c.e. • dalton...

MEASUREMENT & ATOMIC THEORYHonors Chemistry Unit 1

MEASUREMENT

TYPES OF DATA

• Qualitative• Words and Descriptions• EX: red truck, large pizza, soft

puppy• Quantitative

• Numbers and Measurements• EX: 1.4 g, 0.052 mL, 524 cm

Example: Marcus caught a large red octopus off the Pacific coast of South America. It was a strange octopus because it only had seven legs and weighed 18.4 kg. After Marcus got it on the boat, it broke free and ate 4 smelly, dead fish before jumping back into the dark blue sea.

SCIENTIFIC MEASUREMENTS:

• Benefits of SI measurement system• To improve communication• Convenience• Diminish likelihood of errors

SI BASE UNIT USE IN CHEMISTRY

Quality Unit Name Abbreviation Tool to MeasureLength Meter M Ruler/Meter stickMass Kilogram Kg BalanceTime Second S Clock/StopwatchTemperature Kelvin K ThermometerAmount ofSubstance

Mole Mol ---

SCIENTIFIC MEASUREMENTS:

• Derived Unit• Combination of basic SI units• EX: Density (mass/volume) etc.

• Purpose of SI prefixes• Easy conversion between

magnitudes of numbers • Based on powers of 10

METRIC PREFIXES - MEMORIZE

WARM UP – 1/23

• Where is the fire extinguisher?• What do you do if you get something in your eye?

• Which is larger a mL or a ML? What about a cg of a ng?

MEASUREMENT AND UNCERTAINTY

• Measurement: something with a magnitude and a unit that is compared to a standard

• Why uncertain?• Smallest (last) digit is always

estimated by the human or the instrument

MEASUREMENT VOCAB

• Accuracy: how close measurement is to “true” value• Precision: how close measurements are to one another (consistent,

reproducible)• Percent Error: % off the experimental result was from the “true” value

• % 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑉𝑉𝑇𝑇𝑇𝑇𝑉𝑉𝑇𝑇 −𝐸𝐸𝐸𝐸𝐸𝐸𝑇𝑇𝑇𝑇𝑇𝑇𝐸𝐸𝑇𝑇𝐸𝐸𝑇𝑇𝑇𝑇𝑇𝑇 𝑉𝑉𝑇𝑇𝑇𝑇𝑉𝑉𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑉𝑉𝑇𝑇𝑇𝑇𝑉𝑉𝑇𝑇

× 100

ACCURACY AND PRECISION EXAMPLES

ESTIMATED DIGITS

• How we determine where to round the last digit.

• You must use these in EVERY lab and all equipment

• Triple Beam Balances• Thermometers• Rulers• Graduated Cylinders

EXAMPLE

EXAMPLE

EXAMPLE

SIGNIFICANT FIGURES

Name Does it Count? ExampleNon zero number Always 147 cm (3 SF)Leading zeros Never 0.0092 L (2 SF)Middle zeros Always 2008 years (4 SF)Trailing zeros Only if decimal in # 400 g (1 SF) 400. g (3 SF)

MATH WITH SIGNIFICANT FIGURES

Addition or Subtraction• Keep same number of decimal

places as the one with the fewest

• 123.25 mL46.0 mL

+ 86.257 mL255.507 mL

• The rounded answer is 255.5 mL

Multiplication or Division• Keep same number of sig. figs.

As the one with the fewest• 23.0 cm

432 cmx 19 cm188,784 cm3

• The rounded answer is 190,000 cm3

WARM UP – 1/24

• How many significant figures are in the following numbers?• 0.00100• 70400• 1.00090• 1200

• Complete the following mathematical operation and round your answer to the correct number of significant figures.

• 12.00 + 1.987 = • 202 / 2.0 = • 18.39175 * 6 =

GRAPHS AND TABLES

• Almost always use LINE GRAPHS• Tables and Graphs should always

have the following (if applicable)• Labeled axis with units• Even scales of axis• Titles• Headings on columns and rows

GRAPH RELATIONSHIPS

Direct Inverse (Indirect)

DIMENSIONAL ANALYSIS (SORRY THIS DIDN’T MAKE IT INTO THE ONLINE PPT)

• You MUST learn this method. (Even though there are other ways to do it)

• BOX method• How many seconds are in 4.16 hours?

EXAMPLE

• Convert 4.5 ng to mg

EXAMPLE

• Convert 1.5 dm to hm

YOUR TURN

• How many seconds old were you on your last birthday?

MAKE IT HARDER!

• Convert 72.26 mph to meters/second

WARM UP - 1/28

Study for your quiz!!!

ATOMIC THEORY

MATTER

Pure Substances• Elements• Compounds: atoms of two or

more elements chemically combined

• Smallest unit of an element is an ATOM

Mixtures• Heterogeneous: different

throughout• Homogeneous: same throughout

SUBATOMIC PARTICLESParticle Symbol Relative

ChargeRelative Mass

Location in atom

Proton P+ or 11𝐻𝐻+1 1 Nucleus

Neutron 10n 0 1 Nucleus

Electron e-1 or 0−1e -1 0 Electron Cloud (Not the Nucleus)

SUBATOMIC PARTICLES

• The atom consists of three subatomic particles,

• Proton• Neutron• Electron

VOCAB• Nucleons: Particles in the nucleus

(protons and neutrons)• Atomic Number: The number of protons

in the atom. Identifies the element• Mass Number: The number of protons +

neutrons in the nucleus (a whole number)

• Atomic Mass: AVERAGE atomic mass of all of the isotopes (a decimal)

• Isotopes: Atoms of the same element with varying numbers of neutrons

MORE VOCAB

• Nuclide: Any specific isotope of an element

• EX Carbon – 12 Uranium – 235

• Ion: atom with a charge (# e-

not equal to # p+)• + ion (cation) lost e-

• - ion (anion) gained e-

ISOTOPE NOTATION

• Atomic Number ______________

• Mass Number ________________

• # protons ____________________

• # electrons __________________

• # neutrons ___________________ 1327𝐴𝐴𝐴𝐴+3

ATOMIC MASS• All atomic masses

based on mass of Carbon -12

• Unit is AMU or U (atomic mass unit)

AVERAGE ATOMIC MASS

• Weighted average of all of the isotopes in a sample of an element

• ∑ % 𝑖𝑖𝑖𝑖 𝑑𝑑𝑒𝑒𝑑𝑑𝑖𝑖𝑑𝑑𝑑𝑑𝐴𝐴 𝑓𝑓𝑒𝑒𝑒𝑒𝑑𝑑 × (𝑀𝑀𝑑𝑑𝑀𝑀𝑀𝑀 𝑒𝑒𝑓𝑓 𝑖𝑖𝑀𝑀𝑒𝑒𝑖𝑖𝑒𝑒𝑖𝑖𝑒𝑒)

• EX: Calculate the average atomic mass of boron if a sample contains…19.78 % boron-10 (atomic mass = 10.013 u)80.22% boron-11 (atomic mass = 11.009 u)

WARM UP – 1/29

• What is the average atomic mass of element X. 92.23 % exists as X-28, 4.67% exists as X-29, and 3.10% exists and X-30..

• Determine the number of each subatomic particle in• Chlorine – 36

• 1940𝐾𝐾+1

ATOMIC HISTORY

• Democritus proposed the first idea of the atom around 430 B.C.E.

• Dalton proposed the first atomic theory in 1805

• Dalton’s Atomic Theory• All matter is made of

indivisible atoms• Atoms of the same element

are the same• Atoms of different elements

are different• Atoms combine in whole

number ratios

BEFORE DALTON…

• Antoine Lavosier (1794)• Law of Conservation of Mass:

Matter can’t be created or destroyed, only rearranged

• Joseph Proust (1797)• Law of Definite Proportions:

elements for compounds in the same proportions EVERY TIME

• EX H2O is always 2 H and 1 O

• Dalton combined these to make the Law of Multiple Proportions• Elements combine in whole number ratios to make different

compounds• EX: CuCl and CuCl2 CO and CO2

DALTON’S THEORY SUPPORTED BY

• Gay-Lussac (1808)• Law of Combining Volumes

• At constant temperature and pressure, volumes of reacting gases and gaseous products are in the ratio of small whole numbers

• Amadeo Avogadro (1811)• Avogadro’s Hypothesis

• Equal volumes of gases, under the same conditions have the same number of particles

• Avogadro’s number = 6.022 x 1023

• Avogadro’s number is the number of particles in 1 mole

DISCOVERING SUBATOMIC PARTICLES

• J.J. Thomson: discovered the electron with the cathode ray tube experiment

• Modified rays were used to discover protons as well

• Called the plum pudding model

DISCOVERING SUBATOMIC PARTICLES

• Robert Millikan (1911)• Oil Drop Experiment

determined the charge on the electron

DISCOVERING SUBATOMIC PARTICLES

• James Chadwick (1932)• Discovered the neutron by

bombarding beryllium atoms with radioactive particles which produced carbon and a high energy neutral particle – the neutron

REVISIONS TO DALTON’S ATOMIC THEORY

• Describe Dalton’s Atomic Theory:• All matter is made of atoms

that are indivisible• Atoms of the same element

are the same• Atoms of different elements

are different• Atoms combine in whole

number ratios to make compounds

• Atoms can be divided • subatomic particles

• Atoms of one element are not identical

• isotopes and ions• DO have the same number of

protons

THE NUCLEUS

• Ernest Rutherford (1911)• Discovered the nucleus

through the gold foil experiment

STUDY TOPICS• SI Units• Metric Conversions• Dimensional Analysis• Significant Figures• Calculations with Sig Figs• Atomic Theory

• Scientists• Experiments• Conclusions• Models

• Metric Prefixes• Percent Error

• Vocab & Definitions• P+, n, e-, Z, A• Scientific Notation• Average atomic mass

calculations• Safety• Reading equipment• Graphing• Types of data• Density• Using the reference packet