AP CHEMISTRY Chapter 1 Chemical Foundations
Review • Scientific method • SI system -know prefixes inblueon pg 9 • Mass vs weight-an object’s mass reflects the amount of matter it contains. An object’s weight is the pull of gravity on that matter.
Uncertainty Measurements should include all certain digits plus the first uncertain digit. Ex. Reading thermometer, buret, balance, etc. (On digital devices, the last digit shown is uncertain) So what is the reading from this graduated cylinder? How many decimals are acceptable here? The reading should be 52.8 ml where the 8 is the estimated digit.
Accuracy and Precision Which is which??
How Many Significant figures? _____ 7.0023 _____ 4.00 _____ 0.03000 _____ 0.009 _____ 1,000 5 3 4 1 1
Significant Figures in Calculations: • A Review: • When adding and subtracting, use the smallest number of decimal places. • Ex. 3.0 + 6.00 = 9.0 • When multiplying or dividing, use the smallest total number of significant figures. • Ex. 3.0 x 6.00 = 18 • Exact numbers like constants have unlimited significant figures and should not be used to determine the significant figures in a calculation.
Know the differences in temperature scales and know how to convert between each. Tc = (5/9)*(Tf-32) Tf = (9/5)*Tc+32 0°C = 273.15K
Review: • Density D = m/v • Classifications of matter • Separation of mixtures -distillation -filtration -chromatography
AP CHEMISTRY CHAPTER 2 ATOMS, MOLECULES, AND IONS Revealing the hidden atom in graphite with AFM showing all atoms within the hexagonal graphite unit cells. Image size 2×2 nm2.
The Greeks • In 400 BC, the Greek Aristotle determined that there were four fundamental substances (earth, air, fire and water). • The Greeks were unable to test these theories. • Democritus- stated that matter was composed of small indivisible particles called "atomos” -tom = to divide atom = can't be divided
The Alchemists • Over the next 2000 years, Aristotle’s works influenced a branch of science called alchemy that was focused on trying to turn cheap materials into gold. • Thisled to the discovery of some elements and compounds like HNO3, H2SO4, HCl, and aqua regia (HNO3 and HCl). • Also, some scientific procedures were developed.
Robert Boyle -1600's • First person to perform quantitative experiments with a focus on gases • Wrote a book called "The Skeptical Chymist" • His research destroyed the notion of only four elements
Phlogiston theory- (John Becher & George Stahl) postulated that a substance called phlogiston flowed out of burning material during combustion and that materials stopped burning when the phlogiston level became too high. J.J. Becher
Joseph Priestly -1700's -credited with discovery of oxygen (called it dephlogisticated air) Priestly’s equipment used to test “airs”.
-He determined the nature of combustion with careful quantitative procedures. -He developed the law of conservation of mass (mass is neither created nor destroyed) -Disproved the phlogiston theory and named oxygen -Wrote first chemistry textbook (Elementary Treatise on Chemistry) -Was executed by guillotine during French Revolution Antoine Lavoisier
Proust- 1800's -Law of definite proportion- a given compound always contains exactly the same proportion of elements by weight. If we chance the amounts, it changes the identity of the compound. -matter is discrete, or particulate, not continuous
John Dalton -Law of multiple proportion When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small, whole numbers.
Law of Multiple Proportions -can't deduce absolute formulas -shows that each element consists of a certain type of atom and that compounds were formed from specific combinations of atoms.
Dalton’s Atomic Theory (1808) Each element is made up of tiny particles called atoms. The atoms of a given element are identical -the atoms of different elements are different in some fundamental way or ways.
Dalton’s Atomic Theory(continued) Chemical compounds are formed when atoms combine with each other.A given compound always has the same relative numbers and types of atoms. Chemical reactions involve reorganization of the atoms- changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.
Avogadro's Hypothesis- Gay Lussac and Avogadro studied the volumes of combining gases. This allowed them to determine correct formulas. • At the same temperature and pressure, equal volumes of different gases contain the same number of particles. • It was then determined that various gases are diatomic and correct atomic weights were calculated for them by comparing volumes of reacting gases.
Gay-Lussac's Law- when gases are involved in chemical reactions, they always react or appear in small whole-number ratios by volume as long as the temperature and pressure remain the same.
JJ Thomson 1898-1903 -discovered electrons -used cathode ray tube (see diagram) -ray is produced at the negative electrode and is repelled by a negative field.
-Thompson assumed that the ray was a stream of negative particles -He measured the amount of deflection of the beam by a magnetic field and determined the charge-to-mass ratio of an electron.
-Thompson also found that electrodes made from any metal produced cathode rays so he assumed that all atoms contain electrons -He knew that the atom was neutral, so the rest must be positive -From this he devised the Plum Pudding Model
Robert Millican -1909 -determined the mass of an electron through the use of charged oil droplets. He found the charge of an electron and used this, along with the charge/mass ratio to find the mass.
Becquerel -1896 • -discovered radioactivity • -studies found 3 types of emissions: • gamma -high energy light • (no charge) • beta - high speed electron • (1- charge) • alpha -helium nucleus • (2+ charge)
Rutherford's Gold Foil Experiment -1911 -shot alpha particles through gold foil. Most went straight through, a few were deflected This showed that the atom was mostly empty space with a dense, positively charged center.
Nucleus (protons and neutrons) -very tiny Electrons -determine chemical behavior Isotope - atom with the same number of protons but different number of neutrons
The mass number is the number of protons + the number of neutrons “A” is the mass number of the element E A Z “E” is the symbol of the element “Z” is the atomic number of the element The atomic number is the number of protons. In a neutral atom, this is also the number of electrons.
Review: • covalent bonds • Molecule • Formation of ions • ionic bonds • periodic table A bond between two nonmetals in which electrons are shared. A chemical compound made up of nonmetals. Occurs when an atom gains (becomes positive or cation) or loses e- (becomes negative or anion). A bond between a cation and an anion. A chart of all of the elements.
CuI copper(I) iodide or cuprous iodide
NaHCO3 sodium hydrogen carbonate or sodium bicarbonate
HClO2 chlorous acid
selenium tetrabromide SeBr4
hypochlorous acid HClO
K2C2O4 potassium oxalate