It matters how much matter matters.

Review Matter is made up of either elements or compounds. Elements are pure substances made of one kind of atom. They cannot be broken down into simpler chemical substances. Compounds are two or more elements chemically combined into an unchangeable proportion. They can be broken down into simpler substances. A Chemical formula indicates how many of each element is in the compound The amount of matter is often measured in 3 ways Mass in grams (100 grams of potato chips) Volume in liters (2-liter bottle of soda) By count (12 eggs)

Chemical Quantities Measuring by Count: Atoms in a sugar molecule Demonstration: Sugar & Sulfuric Acid (draw in your notes & make 3 observations) Sugar is made from carbon, hydrogen and oxygen. The addition of sulfuric acid causes bonds to break (absorb energy), form new bonds (release energy) and produces carbon and water Formula for sugar: C 12 H 22 O Carbon 22 Hydrogen 11 Oxygen

Elements & Compounds Which element is most abundant in a sugar molecule; carbon, hydrogen, or oxygen? Hydrogen has the most atoms in the molecule, but only makes up 6.49% in terms of mass Oxygen has the fewest but makes up 51.41% of the mass of sugar. How is that possible? Oxygen is much more massive. In fact, it has 16 times the mass of hydrogen.

Elements & Compounds Atomic Mass: The weighted average of the masses of all the isotopes of an element. Found on the Periodic Table Measured in amu (atomic mass units) Atomic masses on the P.T. are not exact masses but are averages of all the isotopes multiplied by their abundance in real life. Examples: Atomic mass ofcarbon hydrogen oxygen = amu = amu = 1.01 amu

Elements & Compounds Formula Mass: the sum of the atomic masses of all the atoms in a chemical formula. Examples:C 12 H 22 O 11 carbon:12.01amu x12 atoms= hydrogen: 1.01amu x22 atoms= oxygen:16.00amu x11 atoms= For sig. figs, assume the atomic masses in the P.T. are measurements amu 22.22amu amu amu Find the formula masses for: H 2 O CO 2 Na 2 SO 4 CH 2 O Fe 2 O 3 C 6 H 12 O 6

Percent Composition  Percent composition: percent by mass of a element that is contained in a compound  total mass of the element divided by the total mass of the compound, multiplied by 100.  Example: What percent does hydrogen make up in Sucrose, C 12 H 22 O 11 ? Carbon:12 atoms x 12.01amu = Hydrogen:22 atoms x 1.01amu = Oxygen: 11 atoms x 16.00amu = amu amu amu amu % comp = 22.22amu amu x100 % comp = 6.49% } the part } the whole

Percent Composition  % composition formula works with mass in grams too Example: 200.grams of sugar was decomposed into 84.5grams of carbon. What percent is carbon in the sucrose? 84.5g carbon 200.g sucrose % mass of carbon = x 100 % mass of carbon =42.25%

Hydrates Hydrate – a substance that has a specific number of water molecules bonded to each of its formula units. Most often a salt Example: sodium carbonate decahydrate: Na 2 CO 3 ∙10H 2 O The dot represents a loose bond between Na 2 CO 3 and H 2 O Coefficient shows how many water molecules are in the formula What percent of water (H 2 O) is in the hydrate Na 2 CO 3 ∙10H 2 O? Use % composition formula Na: 22.99amux 2 atoms : C: 12.01amux 1 atom : O: 16.00amux 3 atoms : H: 1.008amux 20 atoms: O: 16.00amux 10 atoms: 45.98amu 12.01amu 48.00amu 20.16amu amu amu } the part } the whole % comp = (20.16amu amu) x amu % comp = %

Empirical Formula ● Chemical (molecular) formula tells us the precise number of atoms in a compound ● Empirical formula – the simplest ratio of atoms in a compound ● Ex. glucose: C 6 H 12 O 6 ● ratio is 6:12:6, which can be reduced to 1:2:1 ● therefore, the empirical formula for glucose is CH 2 O ● Ex:N 2 H 4 → C3H6→C3H6→ Na 2 CO 3 → NH 2 CH 2 Na 2 CO 3

Empirical Formula Molecular Formula from Empirical Formula · Determine the molecular formula for hydrazine if the empirical formula is NH 2 and the formula mass is 32.06amu. Step 1: Find the empirical formula mass. nitrogen:1 atomx14.01amu= hydrogen:2 atomsx 1.01amu= Step 2: Divide the formula mass given by the empirical formula mass. Step 3: Take the result and multiply it the number of atoms in the empirical formula 14.01amu +2.02amu 16.03amu formula mass:32.06amu empirical formula mass:16.03amu = 2 N (1x2) H (2x2) =N 2 H 4

Density ●Review: ●Mass – the amount of matter in a given object ●Measured in grams & kilograms ●Volume – the amount of space an object takes up ●Measured in liters or cm 3 (cubic centimeters) ● Mass and volume are extensive properties- properties that depend on how much of it one has ●Density- the amount of mass per unit volume of a substance. ●how much stuff is in a particular substance ●intensive property- physical properties that do not rely on the amount ●for pure substances, density does not change whether one has 1 gram of a substance for 1,000,000 grams. ●Densities of several substances are found on the R.T. ●Formula: Unit is either g/mL or g/cm 3 Density = mass volume

Density ● What is the density of grams of water that is contained in a 100.0mL graduated cylinder? What is the volume in milliliters of 75 grams of corn oil that has a density of 1.15 g/mL? What would the volume be for 200. grams of aluminum(Aluminum density is listed on Pg.1 of NC R.T.) ?