Physical • Physical properties can be observed without changing the substance into a different substance. • Color • Shape • Mass • Density • A physical change can be determined without altering the chemical makeup of the material. The identity of the substance is not changed. • Any phase change like melting ice, freezing water • Sharpening pencil • Squashing a bug
Physical Methods of Separation • Chromatography- separation of compounds, usually dyes. The more soluble a compound is in the carrier solvent the further it will travel on the paper. • Fractional Distillation- separation of miscible liquids. The solution is heated until boiling. As liquids have different boiling points the one with the lower BP will go out first into a separate container to be cooled and condensed as pure.
Physical Methods of Separation • Distillation- heating of a liquid with a soluble solid in it. Heat until boiling, it moves through • Evaporation- used to separate solid from liquid. Heat until the liquid evaporates off leaving the solid behind. • Filtration- used to separate insoluble solid from a liquid. Solid remains on the filter paper while the liquid is pulled through.
Chemical • Chemical properties can be observed only when a substance is changed into a different substance. • Ability to burn • Ability to rot • Ability to grow • A chemical change can often be detected by observing the formation of a solid material, a color change, a change in the surface of a solid material, formation of bubbles, or a temperature change (indicating that heat has been absorbed or given off.) • Burning pencil • Bug decaying after squashing • Metal rusting
STP vs SATP • STP – standard temperature and pressure • 0.00˚C or 273 K • 1 atm= 760 mmHg = 760 torr = 101 kPa • SATP – standard ambient temperature and pressure • 25.0 ˚C or 298 K • 1 atm = 760 mmHg = 760 torr = 101 kPa
Isotopes • Atoms with the same number of protons and electrons but differing numbers of neutrons. • Percent abundance of isotopes: • Be able to calculate percent abundance • Deals with fraction math • The whole is 1 or 100 (decimal or percent) • X + Y = 1 solve for Y Y = 1-X • Average atomic mass = mass A (x) + mass B (1-x) • Be able to average atomic mass
Isotope Example The element, europium, exist in nature as two isotopes: Eu-151 which has a mass of 150.9196 amu and Eu-153 which has a mass of 152.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the abundances of the two isotopes.
Limiting Reactant Step 1: write out balanced equation. Step 2: convert each reactant to mass of product Step 3: the reactant that makes the LEAST amount of product is the limiting reactant.
What mass of Ag₂S is produced from a mixture of 2.0 g Ag and 2.0 g S ? Step 1: 16 Ag + S₈ 8Ag₂S
Formulas • The empirical formula of a chemical compound indicates the simplest whole number ratio of the different kinds of atoms that make up that compound. • A molecular formula indicates the exact number of each type of atom that makes up a particular compound. • Often, compounds may share the same empirical formula but have different molecular formulas because they have different multiples of the empirical formula.
% mass mass moles ÷ by small X ‘til whole
Empirical FormulaSample Problem • The percent composition by mass of a compound is 56.6 % potassium, 8.7 % carbon, and 34.7 % oxygen. Determine its empirical formula.
Red Flag Numbers 0.25 0.33 0.5 0.67 0.75 Multiply by: 4 3 2 3 4
Molecular FormulaSample Problem Analysis of a compound indicated that its empirical formula is C2H4O and its molar mass was 176.0 grams/mole. What is the molecular formula of this compound?
Energy, Wavelength, and Frequency • Two formulas: • E = hν E= energy h = 6.63 x 10 ^-34 J s Plank’s constant ν = frequency • c= λν c= 3.0 x 10^8 m/s speed of light λ = wavelength ν = frequency
Last Bit • Be able to convert between moles, molecules, and grams • Be able to name ionic compounds, covalent compounds, and acids • Combustion problems • Polyatomic ions