chemistry
UNIT 3
UNI 4
UNIT 1
Solids
Liquids
gases
tight compact arrangement
loose arrangments
losse but still touching arrangments
Relative atomic mass
Isotopes
Different form of elements with the same number of protons but different number of neutrons
Sum of (isotope abundance + isotope mass) ÷ 100
highest energy
medium energy
lowest energy
Changes of state
Atoms
Elements
Compounds
The smallest particle of an element
2 or more substances chemically combined
Element made of one type of atom
Mixtures
not chemically joined substances but can be seperated
seperation techniques
Solubility
How much a substance will dissolve in a given volume of a solvent
surface area of solute
increase rate of stirring
Diffusion
The net movement of particles from an area of low concentration to high concentration
increase conc. gradient
larger surface area
Exothermic
Endothermic
heat exiting
heat entering
Increase temperature
Solvent
Solute
solution
saturated solution
substance that boils over a range of temps will be a mixture not a pure compound
factional distillation
components of a chemical mixture is separated in fractions by their different boiling/ melting points
crystalisation
the solidification of a liquid substance (must add heat)
simple distillation
purifying a liquid compound by heating into vapour then condensed back into a liquid
temperature of solvent
rf values
distance travelled by pigment ÷ distance travelled by solvent
chemical substance that dissolves a solute = solution
substance being dissolved
homogeneous solution of 2 or more substances (can exist in any phase)
maximum amount of solute that dissolves in a solvent (crystals may form)
vibrate against each other
slide around each other
move and collide with each other
UNIT 2
atomic structure
protons
neutrons
electrons
-1 charge
+1 charge
0 charge
1/2000
1 (mass)
1 (mass)
Alkali metals
lithium
sodium
Potassium
- floats on surface + bubbles
melts into sphere + moves on surface quickly + bubbles
lilac flame + floated rapidly
They all turn universal indicator blue
reactivity
reactivity increases as you go down group 1 because the electrons are arranged so there is one extra electron on the outermost shell. This makes it reactive. as the distance from the nucleus to the single electron increases, the reactivity does as well
positive always attract negatives
the attraction between the positively charged nucleus ad the outermost electrons get weaker as the atom size increases. it makes it easier to lose the outer electron
noble gases
not reactive because already have complete outer shell
isotopes
atoms of the same element but with different number of neutrons but same number of protons
electrons determine the chemical behaviour
relative atomic mass
average mass of all the different isotopes
ionic bonding
electrostatic attraction between oppositely charged ions in a chemical compound.
covalent bonding
formed between atoms when pairs of electrons are shared
molecular ions
electrostatic force of attraction between positively charged ions. (very strong and need stronger input of energy to overcome
ionic compounds have high melting points
electrostatic attraction between a shared pair of electrons and the nuclei on two atoms (very strong)
covalent molecules have low melting and boiling points
weak electrostatic forces between molecules (weak amount of energy to overcome)
non metal + non metal
non metal + metal
rates of reactions
for particles to react, they must have sufficient amount of activation energy to react with each other
catalyst
temperature
surface area
as the temperature increases, the rate of reaction also increases since the particles have more kinetic energy making them move around faster which results in more successful collisons per unit time.
pressure
a catalyst is a substance that is added to a chemical to speed up the reaction. catalyst will lower the activation energy and allow a new pathway for the particles to bond. this will increase the rate of reaction and form more successful collisions per unit time
the rate of reaction will increase with a larger surface area because more particles are exposed to the reactant meaning there will be more successful collisions per unit time.
concentration
at a higher concentration, the rate of reaction will be quicker because there will be more reactant particles in a set volume.
As the pressure increases so does the rate of reaction. Increased pressure is when particles are pushed together in an area so there will be smaller amount of space to move around. this means there will be more chance of successful collisions per unit time
rate of reaction = change in reactant / time
activation energy is the minimum amount of energy for the reaction to start happening and to provide energy for the particles to start moving
ion
atom or a group of atoms with one or more positively or negatively charged electron
molecules
a group of atoms bonded together
unit 6