bonding, structure and the properties of matter Flashcards
process from solid to gas and vice versa
sublimation
difference between evaporation and boiling
evaporation - particles leave liquid from surface only
boiling - bubbles of gas form throughout liquid
what is stronger, ionic bonds or bonds between simple molecules
ionic bonds
2 limitations of the particle model
- particles mostly empty space
- not spherical
how is an ionic bond formed
when a metal and a non-metal react with each other
what is an ionic lattice
the regular arrangement of irons in an ionic substance
how are ionic lattices held together
with strong electrostatic forces
which direction do forces of attraction from ions act in
all directions
why do ionic compounds have high boiling and melting points
because of their strong electrostatic forces of attraction
what do strength of ionic bonds depend on
the charge of ions, higher charge will have stronger forces
when can a substance conduct electricity
- if it contains charged particles such as ions
- can move place to place
when can an ionic compound conduct electricity
- when it’s melted to form a liquid
- dissolved in liquid to form aqueous solution
where does covalent bonding mostly occure
in non-metal elements
what is a double and triple bond in covalent bonding
double - 2 shared pairs of electrons
triple - 3 shared pairs of electrons
why do small molecular substances have low melting and boiling points
they have weak intermolecular forces in comparison to the covalent bonds in the molecules
how to change strength of intermolecular forces
bigger the molecule, stronger the intermolecular force
can covalent bonds conduct electricity
no
what happens to covalent bonds when substances melt or boil
they don’t change
what are melting and boiling points on giant covalent structures
very high, large amounts of energy needed to overcome strong covalent bonds
can giant covalent structures conduct electricity
no except for graphite
how is diamond structured
- each carbon atom joined to four others by strong covalent bonds
- repeating tetrahedal structure
- no free electrons
how is graphite structured
- each carbon atom jointed to 3 others by strong covalent bonds
- carbon atoms form layers of hexagonal rings
- no bonds between layers
- one delocalised electron from each atom
why is graphite good as a lubricant
it’s slippery as the forces between layers are weak so easily slip off
why does graphite conduct electricity
has delocalised electrons that are free to move between layers
properties of graphene
- very high melting point
- very strong
uses of graphene
electronics because delocalised electrons can move freely
what are fullerenes
molecules of carbon atoms with hollow shapes
what is buckminsterfullerene
molecules made of 60 carbon atoms which are spherical
why is buckminsterfullerene slippery
weak intermolecular forces between each molecule that need little energy to overcome, also has low melting point
what is a nanotube
like a layer of graphene rolled into a cylinder
properties of nanotubes
- strong in tension resist being stretched
- conduct electricity
uses of nanotubes
nanotechnology and electronics
what is a polymer
a large molecule formed by many smaller molecules known as monomers
what are the intermolecular forces between polymer molecules
strong compared to forces between small molecules, high melting and boiling point solid at room temp
what is metallic bonding
giant structure of metal atoms and delocalised electrons moving between them
why are metals good conductors of thermal energy
delocalised electrons transfer their energy
why do metals have high melting and boiling points
large amounts of energy are needed to overcome metalling bonds in melting and boiling
what is an alloy
a mixture of two or more elements where at least one is a metal
why are alloys formed
many pure metals are too soft so combining with another makes it harder
why is an alloy stronger than a pure metal
atoms of different sizes, distort the layers of atoms, greater force required for layers to slide, alloy is harder and stronger
what is nanoscience
study of structures between 1 and 100nm in size (nanoparticles)
what is a substance made of nanoparticles called
nanoparticulate
uses of nanoparticulates
zinc oxide is invisible when a nanoparticulate used in suncream, rather than white when in bulk
why are nanoparticulates used as catalysts
they have a large surface area to volume ratio
- more efficient
- catalyse different reactions producing different products
possible risks of nanoparticles
- small size makes it easy to breathe in
- can catalyse harmful reactions in body
- toxic substances can bind because of large SA:VOL ratio
