Chemistry Summary
Chapter 1: The Particulate Nature of Matter
2.1
Solids: 1.) strong forces (because of lattice arrangement) 2.)particles don’t move or flow(definite
shape and volume) 3.) particles vibrate (the hotter they are, the more they vibrate, causing solids to
expand slightly when heated).
Liquids: 1.)weak force of attraction 2.)random arrangement of particles. 3.) Definite volume, but no
definite shape (since can flow to fill the bottom of container). 4.) particles constantly moving with
random motion, the hotter they are, the faster liquids move, which causes liquids to expand slightly
when heated.
Gases: 1.)force of attraction very weak- so particles free to move. Particles in gases travel in straight
lines. 2.) No definite shape or volume, always fill container. 3.) particles move constantly with random
motion, the hotter they are, the faster the gas particles move. Gases either expand when heated or
their pressure increases. 4.) easily compressed.
Changes of state: S-L (melting), L-G (boiling or evaporation), S-G (sublimating-sublimation), G-L
(condensation), L-S (freezing)
Differences between boiling and evaporation: 1.)evaporation can happen at any temperature. 2.)
Boiling happens when a liquid is heated to its boiling point-all liquid evaporates, whereas evaporation
only causes particles with more kinetic energy near the surface of the liquid to evaporate.
2.2
Rate of diffusion depends on: molecular mass of liquid- the larger the molecular mass, the higher rate
of diffusion.
Chapter 2: Experimental Techniques
2.1
Measuring liquids: 1.)Pipettes (suck up an accurate volume of liquid). 2.) Burettes (measure from top
to bottom and have a tap at the bottom. Take initial reading and final reading (difference between the
reading tells you how much liquid you used). 3.) Measuring cylinders (different sizes, the right size
reduces possibilities of error).
Measuring solids: balance (using a container).
Collecting Gases: 1.) Using a gas syringe 2.) By displacing water from a measuring cylinder (-fill
measuring cylinder with water, place it upside down in a water bath. Record initial level of water in
measuring cylinder. - place a delivery tube coming from the reaction vessel inside the measuring
cylinder ( difference in level of water in the measuring cylinder = gas produced).
Measure temperature accurately: thermometer 1.)make sure the bulb of the thermometer is
completely submerged in mixture, but not touching the inside of container. 2.) for initial temperature
wait for temperature to stabilise first. 3.)Read measurement off the scale at eye level to make sure it’s
correct.
Measuring time: stopwatch.
2.2
Pure substance: made up of a single element or compound.
Mixture: more than one compound present, or different elements that aren’t all part of a single
compound.
Testing for purity using melting points: pure substances have specific, sharp melting and boiling
points. You can use this by comparing the actual melting point of a sample to its expected value.
a mixture(impure substances) will melt gradually over a range of temperatures. Impurities will
usually decrease the melting point and increase the boiling point of a substance.
2.3
Chromatography: a method used to separate a mixture of soluble substances and identify them.
,How to draw a chromatogram: 1.)a spot of the test substance is put on the baseline (drawn in pencil)
of a chromatography paper. 2.)End of paper is placed in a solvent, with the solvent just below the
baseline.3.)Solvent travels up the paper through capillary action and carries the test substance with it.
The furthest point the solvent reaches is called the solvent front.4.)The higher the solubility of the
substance in the t.s., the more the substance will travel.
Rf value= distance travelled by substance / distance travelled by solvent
2.4
Distillation: method used to separate mixtures which contain liquids. The method separates out a
liquid from a solution to obtain the liquid.
Distillation method: 1.) solution is heated. 2.) substance of solution with lowest boiling point
evaporates. 3.) vapour is then condensed when it passes through the condenser and is collected in a
beaker as a distillate. 4.)The rest of the solution is left behind in the flask.
Problem of simple distillation: can only be used to separate substances with very different boiling
points; fractional distillation solves this.
2.5
Fractional distillation: same as simple distillation, but can separate liquid substances in mixtures with
similar boiling points.
Fractional distillation method: 1.)put mixture in a flask and stick a fractionating column on top(using a
bung) and then heat it. 2.)The different liquids will have different boiling points, so they will evaporate
at different temperatures. 3.) Liquid with lowest boiling point will evaporate first and rise to the top of
the column, whereas liquid with highest boiling point will also start to evaporate and remain at the
bottom of the column. This is because as the gas goes up the column, the cooler the column gets,
meaning that liquids with high boiling points condense quickly at the bottom. Some don’t even
evaporate in the first place. 4.)Condensed liquids go down the delivery tube to get to the flask.5.)
When the first liquid has been collected, you increase the temperature until the next one reaches the
top.
Boiling points: ethanol: 78ºC, water: 100ºC
Filtration: 1.) Used to separate an insoluble solid from a liquid.2.)Liquid obtained in flask: filtrate,
insoluble solid obtained in filter paper: residue. 3.) Equipment: conical flask, funnel and filter paper.
Crystallisation: 1.) Separates a soluble solid from a solution. 2.)Pour solution into evaporating dish
and heat solution. 3.) When you see crystals starting to form (point of crystallisation) remove dish from
heat and leave the solution to cool. 4.) The salt should form more crystals as it becomes insoluble in
the cold, saturated solution. 4.) Filter crystals out of solution, rinse them with distilled water to remove
any impurities and leave them in a warm place to dry (you could also use a drying oven or a
desiccator-remove water).
Using Solubility to separate substances: 1.) Some substances dissolve better in organic solvents(e.g.
hexane) and others dissolve better in inorganic solvents (e.g. water). 2.) If you have 2 substances
dissolved in water, one of which is more soluble in organic solvents, you can separate them by adding
an organic solvent and shaking the mixture. The second substance will dissolve into the organic
solvent instead. 3.) Organic and inorganic solvents are immiscible, so they will form 2 layers of
solutions that can be separated using a separating funnel or by decantation.
Chapter 3: Atoms, Elements and Compounds
3.1 Atoms
Subatomic particles: Protons: (Relative mass:1, Relative charge: +1), Neutrons: (RM:1, RC:0),
Electrons: (RM:0.0005, RC: -1).
The nucleus: middle of atom,positive, almost whole mass of atom, tiny compared to overall size atom.
, The electrons: The size of their orbitals determines the size of the atom.
Atomic (proton) number: the number of protons/electrons in the nucleus of an atom.
Mass (nucleon)number: the total number of protons and neutrons in the nucleus of an atom.
Isotopes: atoms of the same element which have the same atomic number but a different mass
number.
1.)Some isotopes are stable, but others are unstable and will undergo radioactive decay. 2.)
As these atoms decay, they release energy and small particles until they become stable. 3.)Some
radioactive isotopes are used for medicine(e.g. radiotherapy) and can be used in industry (e.g.
scanning metal machinery).
Electron shell rules: 1.)1st shell: 2 e., 2nd shell: 8 e., 3rd shell: 8 e. 2.)Outer shell reacts to form bonds
with other atoms. 3.) The number of shells in an atom of an element = the period of the element. 4.)
The group number tells you how many electrons are in the outer shell of the element.
3.2 The Periodic Table
- Laid out so elements with similar chemical properties form columns called groups.(Group 1:
alkali metals, Group 2: alkaline earth metals,Group 7: The halogens, Group 8: The noble
gases).
- The rows are called periods.
3.3
Elements: Consist of one type of atom only.
Compounds: 1.) made up of 2 or more different elements chemically bonded together. 2.) Very difficult
to separate the two original elements out again. 3.) Different properties to original elements.
Mixtures: 1.) made up of 2 or more elements/compounds which are not chemically bonded together.
2.)The elements/compounds can be separated out by physical methods (e.g. distillation).3.)
Chemically impure.
Metals:1.) Located on the left side of zigzag (which starts at the left of boron). 2.)Conduct electricity.
3.) Are basic, so can neutralise acids. 4.)Shiny 5.)High melting points.
Non-metals: 1.) Located on the right of the zigzag. 2.) Poor conductors of electricity. 3.) Non-metal
oxides are acidic, so can neutralise bases. 4.) Non-metals that can dissolve in water will form
solutions with a pH of less than 7. 5.) Generally dull and low melting points.
Alloys: a mixture of a metal with other elements. (E.g. brass-> copper and zinc, used in plumbing,
musical instruments, steel-> iron and carbon). (ALERT:alloys don't share the same properties as their
pure metal.)
Ion: a charged particle. It can be either positively or negatively charged.
3.4
Ionic compound: The reaction between a metal and a non-metal to form a salt. The metal atom loses
electrons to form a positive ion (cation) and the non-metal gains these electrons to form a negative ion
(anion).
1.) Lattice structure, which are giant ionic structures. 2.)ions are held together in a closely packed
3D lattice structure by the attraction between oppositely charged molecules (strong
intramolecular forces), so high melting & boiling points, not volatile. .3.) Regular arrangement
of alternating positive and negative ions. 4.) dissolve in water. 5.)Don't conduct electricity
When solid, but do conduct when they are molten or in solution because ions are free to
move and carry electric charge.
3.5
