What is the difference between a mixture and a compound
A compound is a substance that contains two or more different types of atomschemically bonded and a mixture consists of different substances which aren't chemically bonded
What is filtration?
The separation technique which removes large insoluble particles from a liquid
e.g sand from water
What is the process of evaporation and crystallisation?
Leaves behind the solute, solvent is evaporated and dissolved substance is left and if heated gently crystallisation occurs
Define distillation
Involves condensing the evaporated solvent and collecting it
What is fractional distillation?
The process of separating two liquids due to their different boiling points
Chromatography
process for separating components of a mixture
What is the mobile phase in chromatography?
The solvent e.g water
What is the stationary phase in chromatography?
The chromatography paper
Why is the starting line always drawn in pencil
So it won't move
it is also just above the water line
How to calculate Rf value?
distance substance moved/ distance mobile stage moved
Describe the arrangement of particles in a solid (3)
-particles in regular arrangement
-vibrate about fixed positions
-cannot be compressed
describe the arrangement of particles in a liquid (3)
particles have no regular arrangement
particles are able to move past each other
cannot be compressed
Describe the arrangement of particles in a gas (3)
particles are far apart
move randomly at fast speeds
can be compressed
What did John Dalton think of matter?
they were made of indivisible particles
Who created the plum pudding model?
JJ Thomson
What did Rutherford discover and how?
The nucleus is small and positively charged by finding most alpha particles went straight through the gold layer
What did Bohr discover?
Electrons exist in shells
What did Chadwick determine?
The nucleus contained NEUTRONS as well as protons
What is an atomic number?
The number of protons present in the nucleus (smaller number)
What is the mass number?
The amount of protons and neutrons present in the nucleus
Define an isotope
The same element with different numbers of neutrons
Electron shells fill up:
2,8,8,2
Group 1 (3)
Alkali metals (1+)
More reactive as you go down the group
React with water to produce an alkali
Group 7 (4)
Halogens (1- ions)
Less reactive down the group
Boiling point increases down the group
non-metals
accept 1 electron to achieve a full outer shell
Group 8/0 (2)
Noble gases
Very unreactive
What is special about transition metals?
They can donate different numbers of electrons
What is metallic bonding?
The strong electrostatic attraction between the sea of negative delocalisedelectrons and positive metal ions
Ionic Bonding
When metal atoms donate electrons to non-metals to form ions
Ionic bonding
This process can be displayed through a dot and cross diagram
Why can ions only conduct electricity when molten or dissolved?
Because the ions are free to move in there states, carrying charge
Ionic substances (3)
high melting/ boiling points due to strong ionic bonds
ion have strong electrostatic forces between them
arranged in a lattice of repeating units of positive and negative ions
What are the names of positive ions and negative ions?
positive ions are known as cations
negative ions are known as anions
What is covalent bonding? (3)
Non-metals bond to each other
The atoms share electrons to achieve full outer shell
They have low boiling points due to weak intermolecular forces that need to be overcome
Diamond (3)
One of the hardest known substances due to very strong bonds
Each carbon atom is joined to four other carbon atoms
Giantcovalent structure
All giant covalent structures have...
very high melting points as you would have to break the covalent bonds
Graphite
Delocalisedelectrons form weak bonds between layers
Can conduct electricity as the electrons can move
Layers can slide past each other
What is an allotrope?
Structures made of the same element but arranged differently
Use of fullerenes/ nanotubes
Used for electronics, medical purposes
What are moles used for?
To compare quantities of substances
What is the relative formula mass?
the sum of relative atomic masses of the atoms shown