Chap 5 Chem Flashcards
Ionic substances properties
-giant ionic crystal lattice structures
-strong electrostatic forces of attraction
-hard but brittle
-high melting and boiling point (solids at room temp)
-conduct electricity in molten state
-soluble in water, insoluble in organic solvents
Properties of simple covalent molecules
-strong covalent bonds
-weak intermolecular forces of attraction (between molecules)
-change of state in substance during boiling or melting
(breaks weak intermolecular forces of attraction NOT strong covalent bonds)
-low melting and boiling point (affected by size)
-volatile
-insoluble in water, soluble in organic solvent
-cannot conduct electricity (all states)
Allotropes
Different forms of the same element with different structural arrangement of atoms
Giant covalent substances
-hardness (diamond)
very hard (diamond and silicon dioxide)
graphite: layers slide, soft and slippery
-high melting and boiling point
-insoluble in water & organic substances
- cannot conduct electricity: diamond, graphite
can conduct electricity: graphite
Macromolecules physical properties
Most are solids @ room temp (large size)
No fixed bp and mp
Usually soften over range of temp
Insoluble in water, soluble in organic solvents
Do not conduct electricity
Why ionic compounds are hard but brittle (not so impt?)
Hard- attractive forces cause ions to resist motion
Brittle- when force is applied, ions of same charge approach each other, Repulsive forces between ions of the same charge becomes larger than attractive forces -> shatters lattice
Why ionic substances cannot conduct electricity in solid state but can in liquid/aqueous/molten state
Solid- ions not free to move abt, vibrate about fixed positions cannot conduct
Liquid- ions mobile, can conduct
Diff structures of covalent substances
Simple molecular
Giant molecular
Macromolecular
Relationship between Mr/size and intermolecular forces of attraction and mp bp
Larger Mr -> stronger … attraction -> higher mp, bp
Can simple covalent molecules conduct electricity and why
No
Absence of mobile charge carriers/ no free moving ions/electrons
(exception, HCL which dissociates in water and has mobile ions)
Why are allotropes usually in solid state
Many atoms connected by strong covalent bonds
Why giant covalent structures have high mp and bp
Large amt of energy needed to break strong covalent bonds within molecule
Electrical conductivity in giant covalent substances
No - diamond, silicon dioxide (no mobile electrons)
Yes- graphite (free and mobile electrons (delocalised electrons in each layer of carbon atoms))
Why are macromolecules usually in solid state at room temp
Large size of polymers-> strong intermolecular forces of attraction
Why do macromolecules usually soften over range of temp
Weaker intermolecular forces of attraction overcome by molecular vibrations with higher KE
Why do polymers melt and boil over a range of temp
Diff sizes of molecules/monomers
What are alloys
Mixture of metal with one/more elements
Properties of pure metals
-malleable
-ductile
-high mp and bp
-good electrical conductor (sea of delocalised electrons)
-layers of atoms slide over one another easily
Properties of alloys
-less malleable
-less ductile
-harder and stronger than pure metals
-melt over a range of temp (mixture, irregular lattice arrangement)
-good electrical conductor
-larger force needed to make layers slide over one another
Malleable
Ability to be hammered into different shapes
Ductile
Ability to be pulled into wires without breaking
Explain why alloys are harder than pure metals
Alloys contain atoms of diff sizes
Disrupts the regular and orderly arrangement of pure metals
Layers of atoms cannot slide over one another easily
Thus Alloys are harder and stronger than pure metals
Explain mp and bp of ionic compounds
High mp and bp, solids at room temp
Strong electrostatic forces of attraction between oppositely charged ions -> large amt of energy needed to overcome these forces
