principles of chem Flashcards
solid
- close
- regular arrangements
- vibrate in fixed position
- strong force of attraction
- fixed definite shape
liquid
– Close together
– a regular movement
– able to move/flow past each other
– fixed – take shape of container
gas
– Spreadout – far apart – irregular – free to move randomly – weak force attraction – not fixed – expands to fill container
increase in temp.
– Gaining kinetic energy – move more
– energy is used to overcome force attraction between particles
– change in arrangement
evaporation vs. boiling
- any temp.
- slow
- occurs at surface
- certain temp.
- fast
- occurs throughout
- bubbles
gas diffusion bromine gas
- red brown vapour spreads throughout both gas jars (spread out so less concentrated)
liquid diffusion potassium magnate
Purple crystal dissolves and diffuses Slower in liquids than gases – particles have more energy – move faster or more spread – last trailer parks – less collisions If you increase the temperature diffusion happen faster – particles have more KE
gas diffusion ammonia + hydrogen chloride gas
it’s a solid ammonium chloride form when gases meet
it’s not formed in the middle ( closer to HCl because NH three diffuse faster as it has smaller mass)
larger mass = slower diffusion
solute
solid that is dissolved in a solvent e.g. salt
solvent
Liquid the solute is dissolved in eg water
solution
mixture of solute + solvent eg salt water
saturated solution
when no more solute can dissolve in the solvent
insoluble
incapable of being dissolved in the solvent
solubility
A measure of how much solute can dissolve in a given volume of solvent at a given temperature measured in solute per 100 g of solvent
atom
smallest part of an element - cannot be broken down
molecule
two or more atoms chemically bonded together
giant lattice
A regular repeating arrangement of atoms or ions in a giant structure
element
pure substance made of only one kind of atom
- fixed melting / boiling point
compound
A pure substance that contains two or more types of atoms chemically bonded together
– fixed melting/boiling point
mixture
A substance that contains two or more types of elements/compounds not chemically bonded
– may melt/boil over a range of temperatures
metal + non metal >
__ _ide
metal + non metal + oxygen >
_ _ate
non metal + non metal >
_ _ide
ammonia
NH3
methane
CH4
distillation
soluble solid and solvent - keep both
– water boils leaving a soluble solid
– water vapour condenses because of cold water in condenser
– water is collected
fractional distillation
Mixture of miscible liquids with different boiling points – keep both
– heat to liquid1 boiling point
– mixture of liquid1 and some liquid2 water vapour rises + Condenses on beats hitting them up to boiling point1
- liquid1 no longer condenses only liquid2 does so liquid1 goes to condenser + drips into beaker
filtration
separate insoluble solid + solvent - keep both
residue left in filter paper - filtrate goes through to beaker
crystallisation
soluble solid and solvent – only keep solid
– heat until 2/3 as water is gone (saturated solution)
– test using glass rod (crystals form on rod)
- Cool and filter crystals
chromatography
mixture of different solutes - draw pencil origin line + put dot of substance on - add solvent below base line - remove before water reaches top - let it fry result = chromatogram
Rf
Distance solute travelled/distance solvent travelled (baseline –> solvent front)
proton
mass 1
charge 1+
in nucleus
neutron
mass 1
charge 0
in nucleus
electron
mass 1/1800
charge 1-
in shells
mass no
The sum of the number of neutrons and protons in an atomic nucleus
atomic number
The number of protons in the nucleus of an atom (equal to the number of electrons)
Identity of an atom
isotopes
atoms of the same element that have the same no. protons but a diff. no. neutrons
relative atomic mass Ar
weighted average mass of one atom of an element relative to 1/12th of the mass of a C-12 atom
how to work out Ar
(mass no. isotope1 x abundance1) + (mass no. isotope2 x abundance2)/ abundanec1 + abundance2
ions
charged atoms – form when atoms lose or gain electrons to get a full outer shell
cations
positive ions
anions
negative ions
silver ions
Ag +
lead ion
Pb 2+
zinc ion
Zn 2+
hydroxide ion
OH-
nitrate ion
NO3 -
sulphate ion
SO4 2-
carbonate ion
CO3 2-
ammonium ion
NH4 +
ionic bond
The electrostatic attraction between positive and negative ions
ionic bonding
Metal and nonmetal
Gain/loss of electrons
Giant ionic lattice
Formula = ratio of anions to cations in the lattice
physical properties of ionic compounds
- High melting/boiling point – strong electrostatic attraction between anions and cations which requires lots of energy to break
– poor conductor (solid) –ions can’t move - good conductor when molten or aqueous – has charged ions that can move
why some ionic compounds have diff. melting points
The higher the charge of ions and the smaller the ions the stronger the electrostatic attraction between the ions
covalent bond
electrostatic attraction
between the positive nuclei and shared pair of electrons
H- H
covalent bonding
non metal + non metal
sharing of electrons
simple molecular or giant covalent structur
simple molecular structure
atoms bonded covalently with weak intermolecular forces between molecules
physical properties of simple molecular compounds
- Low melting point – weak intermolecular forces are easy to overcome
- Doesn’t conduct electricity – no charged ions/delocalised electrons – molecules are neutral
– formula tells you how many atoms in each molecule
why simple molecular covalent compounds change in melting point
melting points increase as the relative molecular mass of the molecules increase
– bigger RMM = stronger intermolecular forces between molecules
– more energy needed to overcome them
fullerenes
Allotropes of carbon
– have spherical or cylindrical hollow shapes with rings of carbon atoms
– have simple molecular structure
E.g. buckminsterfullerene C60
Have low melting points/boiling point – weak intermolecular forces are easy to overcome
giant covalent compounds
giant lattice structure
consisting of millions of atoms with strong covalent bonds between them
eg diamond graphite silicon dioxide
diamond properties (like most others)
– Hard – strong covalent bonds between atoms
– very high mtp. – lots of energy needed to break strong covalent bonds
– don’t conduct electricity – no ions/delocalised electrons – neutral charged
– uses – drill heads/jewellery
graphite properties
- soft - Exists in layers that can slide over each other – weak forces between layers
– very high mtp. – lots of energy needed to break strong covalent bonds
– good conductors of electricity – contain delocalised electrons that can move throughout structure
– uses – pencils/lubricant
metallic bond
the strong attraction between positive ions and negative delocalised electrons
metallic bonding
metal only
giant metallic lattice
physical properties of metallic compounds
- hi mtp. /bp. – lots of energy needed to overcome strong electrostatic attraction between cations and delocalised electrons
– malleable and ductile – layers of irons can slide over each other
– good conductors of electricity/heat –have delocalised electrons that are free to move throughout the structure

why metallic compounds change in melting point
the higher the ions charge the more delocalised electrons and the stronger the electrostatic force which takes more energy to overcome
