Transcript Ch8 Sec2
CHAPTER 8 Compounds and Molecules 8.2 Molecular Compounds In early chapters we discussed physical and chemical properties ‹#› In later chapters we discussed atom structures and chemical bonding 8.2 Molecular Compounds Physical and chemical properties ‹#› Atom structures and chemical bonding 8.2 Molecular Compounds Ionic compounds (like table salt, NaCl) Physical and chemical properties ‹#› First we addressed ionic compounds Atom structures and chemical bonding 8.2 Molecular Compounds Now we will address molecular compounds which are held together by covalent bonds. Physical and chemical properties ‹#› Molecular compounds (like DNA) Atom structures and chemical bonding 8.2 Molecular Compounds Properties of molecular compounds vary widely Hardness Some are hard and brittle; some are flexible, soft or mushy ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Hardness Some are hard and brittle; some are flexible, soft or mushy State of matter They can be solid, liquid or gas at room temperature ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Hardness Some are hard and brittle; some are flexible, soft or mushy State of matter They can be solid, liquid or gas at room temperature Boiling points Their boiling points can vary from –253oC to over 1,000oC ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Hardness Some are hard and brittle; some are flexible, soft or mushy State of matter They can be solid, liquid or gas at room temperature Boiling points Their boiling points can vary from –253oC to over 1,000oC Ability to conduct electricity Most do not conduct electricity well ‹#› 8.2 Molecular Compounds Water Water is a covalent compound About eight million billion billion (1024) water molecules make up this cup of water Properties of molecular substances depend on: - the structure of the individual molecule - the attractions between molecules ‹#› 8.2 Molecular Compounds Molecules can be classified into different categories Small Caffeine, found in tea, coffee, and soda ‹#› Medium Wax, one of the main hydrocarbons in beeswax 8.2 Molecular Compounds Molecules can be classified into different categories Large: polymer Protein, molecule on the right shows a thick line tracing the linear chain with red and blue marking either end ‹#› Large: network Graphene, layers of which make graphite 8.2 Molecular Compounds Small molecules Most small molecules (no more than a dozen atoms) are liquids or gases at room temperature Some of the most important molecules related to our ecosystem are small molecules ‹#› Acetaminophen (Tylenol) is a liquid at room temperature 8.2 Molecular Compounds Most small molecules (no more than a dozen atoms) are liquids or gases at room temperature Some of the most important molecules related to our ecosystem are small molecules ‹#› If ice did not float, ponds would freeze from the bottom up, killing everything inside. Water 8.2 Molecular Compounds Small molecules Ethene (or ethylene) Ethanol Nonpolar (gas at room temperature) Boiling point = –103.7oC Polar (liquid at room temperature) Boiling point = 78.4oC ‹#› 8.2 Molecular Compounds Medium-sized molecules Medium-sized molecules (no more than 100 atoms) tend to be liquids or soft solids at room temperature. They are often long-chain hydrocarbons or lipids Candle wax is a mixture of medium-sized hydrocarbons hydrocarbon: a molecule made entirely from carbon and hydrogen atoms. ‹#› 8.2 Molecular Compounds Medium-sized molecules Lipids are typically fats or steroids Fats are nonpolar and insoluble in water Linoleic acid, a major component of vegetable oil ‹#› 8.2 Molecular Compounds Medium-sized molecules Most steroids have four rings of carbon atoms. 3 1 They can act as hormones, drugs, vitamins, or poisons 4 2 Testosterone (a steroid) ‹#› 8.2 Molecular Compounds Polymers Polyvinyl chloride (PVC) is made by bonding many vinyl chloride monomers together A single monomer of vinyl chloride A single polymer chain typically contains hundreds to thousands of atoms ‹#› 8.2 Molecular Compounds Polymers Recycling symbols and polymer codes Polyvinyl chloride polymer: a long chain molecule formed by connecting small repeating units with covalent bonds. monomer: a small molecule that is a building block of larger molecules called polymers. ‹#› 8.2 Molecular Compounds Polymers Starch fragment found in food (bread, pasta…) Glucose a natural monomer ‹#› 8.2 Molecular Compounds Polymers Starch fragment found in food (bread, pasta…) Glucose a natural monomer Cellulose fragment makes up wood, paper… ‹#› 8.2 Molecular Compounds Polymers Starch fragment Homopolymers are made from only one type of monomer Glucose a natural monomer Cellulose fragment ‹#› 8.2 Molecular Compounds Polymers Copolymers are made from more than one type of monomer adenine thymine guanine cytosine sugarphosphate backbone nucleotides DNA fragment a heteropolymer ‹#› 8.2 Molecular Compounds Polymers Most proteins are made from up to 20 different monomers called amino acids ‹#› 8.2 Molecular Compounds Polymers Most proteins are made from up to 20 different monomers called amino acids Four of these bind together to form hemoglobin, the protein complex in blood cells that transports oxygen ‹#› 8.2 Molecular Compounds Networks Silicon dioxide (or quartz) is a mineral in sand Since every atom in quartz is covalently bonded together, the entire grain can be considered a single network. network covalent: a type of large structure, usually made from hundreds to billions of atoms, in which each atom is covalently bonded to multiple neighboring atoms, forming a web of connections. ‹#› 8.2 Molecular Compounds Networks Carbon forms many types of network covalent substances Diamond Buckyballs Carbon nanotubes Graphite ‹#› 8.2 Molecular Compounds Chemical formulas Use the empirical formula to describe the simplest ratio of elements of that substance A sample of ionic or network covalent substance is a single bonded unit of material ‹#› 8.2 Molecular Compounds Chemical formulas Use the empirical formula to describe the simplest ratio of elements of that substance a molecule of water A sample of ionic or network covalent substance is a single bonded unit of material ‹#› Use the molecular formula to indicate the exact type and number of each atom in a single molecule of that substance 8.2 Molecular Compounds Chemical formulas a molecule of water Benzene Empirical formula: CH Molecular formula: C6H6 ‹#› Use the molecular formula to indicate the exact type and number of each atom in a single molecule of that substance 8.2 Molecular Compounds Chemical formulas Write the molecular formula for each of the following molecules: ‹#› 8.2 Molecular Compounds Chemical formulas Write the molecular formula for each of the following molecules: ‹#› Asked: The molecular formula Relationships: The formula should reflect the exact number and type of atoms in an individual molecule of the substance. 8.2 Molecular Compounds Chemical formulas Write the molecular formula for each of the following molecules: ‹#› Asked: The molecular formula Relationships: The formula should reflect the exact number and type of atoms in an individual molecule of the substance. Solve: A. C2H2 8.2 Molecular Compounds Chemical formulas Write the molecular formula for each of the following molecules: ‹#› Asked: The molecular formula Relationships: The formula should reflect the exact number and type of atoms in an individual molecule of the substance. Solve: A. C2H2 B. NH3 8.2 Molecular Compounds Chemical formulas Write the molecular formula for each of the following molecules: ‹#› Asked: The molecular formula Relationships: The formula should reflect the exact number and type of atoms in an individual molecule of the substance. Solve: A. C2H2 B. NH3 C. C2H5O 8.2 Molecular Compounds Naming simple molecular compounds Naming organic molecules can be complex Binary molecular compounds have simpler names Carbon dioxide 2-benzyl-1,1-dichlorocyclobutane ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Consider the following molecular compound: P2S3 two phosphorous atoms with three sulfur atoms diphosphorous trisulfide ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Consider the following molecular compound: H2O two hydrogen atoms with one oxygen atom ? ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Consider the following molecular compound: H2O two hydrogen atoms with one oxygen atom dihydrogen monoxide (another name for water) ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Consider the following molecular compound: CO Drop “mono” for the first element ‹#› one carbon atom with one oxygen atom carbon monoxide 8.2 Molecular Compounds Naming simple molecular compounds Write the name for each of the following formulas: N2O4, S2F10, and SO3. ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Write the name for each of the following formulas: N2O4, S2F10, and SO3. ‹#› Asked: Names of the formulas Given: Three formulas and a table of prefix names Relationships: The name of the formula is constructed from the simple ionic name with prefixes before each element, indicating the number of each atom. 8.2 Molecular Compounds Naming simple molecular compounds Write the name for each of the following formulas: N2O4, S2F10, and SO3. ‹#› Asked: Names of the formulas Given: Three formulas and a table of prefix names Relationships: The name of the formula is constructed from the simple ionic name with prefixes before each element, indicating the number of each atom. Solve: N2O4 is dinitrogen tetraoxide. 8.2 Molecular Compounds Naming simple molecular compounds Write the name for each of the following formulas: N2O4, S2F10, and SO3. Asked: Names of the formulas Given: Three formulas and a table of prefix names Relationships: The name of the formula is constructed from the simple ionic name with prefixes before each element, indicating the number of each atom. Solve: N2O4 is dinitrogen tetraoxide. S2F10 is disulfur decafluoride. ‹#› 8.2 Molecular Compounds Naming simple molecular compounds Write the name for each of the following formulas: N2O4, S2F10, and SO3. Asked: Names of the formulas Given: Three formulas and a table of prefix names Relationships: The name of the formula is constructed from the simple ionic name with prefixes before each element, indicating the number of each atom. Solve: N2O4 is dinitrogen tetraoxide. S2F10 is disulfur decafluoride. SO3 is sulfur trioxide. ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Hardness Some are hard and brittle; some are flexible, soft or mushy State of matter They can be solid, liquid or gas at room temperature Boiling points Their boiling points can vary from –253oC to over 1,000oC Ability to conduct electricity Most do not conduct electricity well ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Small molecules Ethene (or ethylene) helps fruits to ripen Nonpolar (gas at room temperature) Boiling point = –103.7oC ‹#› Acetaminophen (Tylenol) Ethanol (or ethyl alcohol) Polar (liquid at room temperature) Boiling point = 78.4oC 8.2 Molecular Compounds Properties of molecular compounds vary widely Small molecules Medium-sized molecules They are often long-chain hydrocarbons or lipids Lipids are typically fats or steroids Candle wax (a mixture of medium-sized hydrocarbons) ‹#› Testosterone 8.2 Molecular Compounds Properties of molecular compounds vary widely Small molecules polymerization n Medium-sized molecules Large molecules Polymer ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Small molecules polymerization n Medium-sized molecules Large molecules Polymer Network Covalent networks ‹#› 8.2 Molecular Compounds Properties of molecular compounds vary widely Small molecules Medium-sized molecules Large molecules Polymer Network P2S3 two phosphorous atoms with three sulfur atoms Naming simple molecular compounds diphosphorous trisulfide ‹#› 8.2 Molecular Compounds