Ch 5.4 Structure and Properties of Materials

Created by

Eden

Cards (51)

What is malleable?
able to be bent or flattened into a thin sheet
What is ductile?
pulled into a wire without breaking
Why are metals malleable and ductile?
"sea of delocalised electrons" continue to hold metal ions together unless much greater force is applied
What happens when pure metals have enough force applied on them and why?
-layers of atoms slide over one another easily
-because pure metals have regular structure
Why are alloys stronger and harder than pure metals? 
-irregular lattice arrangement due to different atom sizes
-due to alloys made up of different elements
-> hence LAYERS slide over one another less easily
Why do pure metals have high melting and boiling points? 
-atoms held together in lattice by strong metallic bonds
-> strong electrostatic forces of attraction
-large amount of thermal energy needed to overcome forces of attraction
Do alloys have a fixed melting point/boiling point? 
No -> melt over a range of temperatures
-> alloys are mixtures
Why are alloys and metals good conductors of heat? 
-delocalised valence electrons collide into each other
-allow efficient transfer of thermal energy throughout giant metallic lattice
Why are alloys and metals good electrical conductors? 
-sea of delocalised electrons able to carry electric charge
-allows electric current to flow
Which has stronger metallic bonding? Sodium or Magnesium?
-Magnesium -> electronic configuration: 2, 8, 2
-has more valence electrons in atom => more delocalised electrons
-> stronger mutual electrostatic forces of attraction
What are some common alloys and their purpose?
-Bronze (copper and tin) -> high hardness and strength
-Brass (copper and zinc) -> high hardness and strength*
-Steel (iron and carbon) -> high hardness *
-Solder (tin and lead) -> low melting point
-Rose gold (copper and gold) -> improve appearance to create new colours
-purple gold (aluminium and gold) -> improve appearance to create new colours
-stainless steel (iron, carbon, chromium, nickel) -> high resistance to corrosion
What are the structural properties of simple covalent molecules?
-atoms in molecule are held by strong covalent bonds
-molecules held together by weak intermolecular forces of attraction
at a low temperature, some simple covalent molecules form a lattice
What kind of melting point or boiling point do simple covalent molecules have?
-low melting point / boiling point
-> weak intermolecular forces of attraction between molecules are easily overcome with a small amount of energy
-some are volatile -> evaporate easily
-exist mostly as a gas / liquid at room temperature
What happens when a simple covalent molecule gets larger?
-molecule gets larger, intermolecular forces of attraction becomes stronger
-> melting point / boiling point is higher
What is the solubility of simple covalent molecules?
-most are insoluble in water
-soluble in organic solvents
Are simple covalent molecules conductors of electricity?
simple covalent molecules exist as neutral molecules
-> do not have any mobile charge carriers to conduct electricity
some simple covalent molecules dissociate in water
-> resulting solution can conduct electricity
What are allotropes?
-different forms of the same element
-same number of protons, different nucleon number
-different structural arrangement of atoms
What is the structure of giant covalent structures?
-almost always in solid state
-consist of many atoms all connected to one another by numerous strong covalent bonds
-> makes them very rigid
-> able to withstand large forces
What is the structure of graphite?
-giant molecular structure
-graphite layers are easily separated from each other due to weak intermolecular forces of attraction exist between layers
-each layer is hard to break apart due to strong covalent bonds found within each layer
What is the hardness of diamond? ( giant covalent structure )
-diamond is hard
-structure is made up of only strong covalent bonds
-large amount of energy is needed to break structure apart / break strong covalent bonds
What is the hardness of graphite?
-graphite is soft and slippery
-small amount of energy is needed to overcome weak intermolecular forces of attraction between layers of carbon atoms
-> layers of carbon atoms can slide over each other easily
graphite is an element
What kind of melting point / boiling point do giant covalent structures have?
-very high melting point / boiling point
-> solids at room temperature
-giant covalent structures are very resistant to heat
-> large number of bonds in network
-large amount of energy is required to break strong covalent bonds between atoms
What kind of solubility does giant molecular structures have?
-most are insoluble in water
-insoluble in organic solvent
Can most giant covalent structures conduct electricity?
giant covalent structures with no electrons do not conduct electricity
Can graphite conduct electricity?
-Yes -> each carbon atom is bonded to 3 other carbon atoms
-> 1 unbonded electron per carbon atom, free and mobile to conduct electricity
What are macromolecules?
another group of covalent substances
What are polymers?
-polymers are macromolecules
-1 polymer consists of many covalent molecules joined together into chains of much larger molecules
What are some examples of natural polymers?
silk, wool, starch, rubber
What are some examples of man-made polymers?
polyester, nylon, polystyrene, other plastics
What are the structural properties of polymers?
-vary greatly in hardness and flexibility
-> exist in so many different combinations of atoms
-made into many different products
What kind of melting point / boiling point do polymers have?
-polymer may be formed by molecules of a range of sizes
-> do not have fixed melting points / boiling points
-large size of polymers -> stronger intermolecular forces of attraction -> solids at room temperature
-polymers typically soften over a range of temperature when weak intermolecular forces of attraction overcome by molecular vibrations with higher kinetic energy
What kind of melting point / boiling point do poly(ethene) have?
-poly(ethene) is a polymer with weak intermolecular forces of attraction between molecules
-melting point / boiling point are low
What kind of solubility do polymers have?
-most macromolecules insoluble in water
-soluble in organic solvents
Can polymers conduct electricity?
-macromolecules unable to conduct elecricity in any state as they do not have mobile ions / electrons
anything in aqueous state can conduct electricity
Does pure liquid oxygen conduct electricity? Why?
-No
-There are no free-moving charged particles
What allows compounds/molecules to conduct electricity?
free-moving charged particles
Does pure liquid water conduct electricity? Why?
-No
-There are no free-moving charged particles