Section 1 - Particles and Matter Flashcards
solids
- strong forces of attraction between particles
- holds particles close together in fixed positions
- solids have definite shape and volume and don’t flow because particles don’t move
- particles vibrate. hotter = more vibrate (causing solids to expand slightly when heated
liquids
- weak force of attraction between particles arranged randomly free to move but tending to stay closer together
- definite volume but not definite shape and will flow to fill bottom of container
- particles are constantly randomly moving hotter = more vibrate (causing liquids to expand slightly when heated
gases
- force of attraction between particles is very weak, they’re free to move and far apart the particles travel in straight lines
- don’t have definite shape or volume and flow to fill container particles move constantly with random motion ( hotter = faster so when heated a gas can either expand or increase pressure)
physical changes of states
(solid) - melt - (liquid) - evaporating - (gas)
(gas) - condensing - (liquid) - freezing - (solid)
(solid) - subliming - (gas)
melting
1) when a solid is heated its particles gain more energy
2) this makes particles vibrate more, weakening the forces that hold the solid together making it expand
3) at a certain temperature particles have enough energy to break free from their positions solid turns to liquid
evaporation
1) when liquid is heated particles get energy
2) this makes particles move faster which weakens and breaks bonds holding liquid together
3) at a certain temp the particles have enough energy to break their bonds. this is called evaporating and liquid turns into a gas
solution
a mixture of a solute and a solvent that does not separate out
solute
the substance being disolved
solvent
the liquid the substance is dissolving into
saturated solution
a solution where the maximum amount of solute has been dissolved and no more solute will dissolve into the solution
atoms
made up of three subatomic partcles
- protons (heavy and positively charged)
- neutrons (heavy and neutral)
- electrons ( hardly any mass and negatively charged )the
the nucleous of an atom
1) its in the middle
2) contains protons and neutrons
3) has a positive charge (because of the protons)
4) almost whole mass of atom is concentrated in nucleus
5) compared to overall size of atom nucleolus is tiny
facts ab the
the electrons
of an atom
- move around nucleus in energy levels called shells
- negitavely charged
- tiny but orbitals cover a lot of space
- size of orbitals determine size of atom
- electrons have virtually no mass
electons and protons in an atom
number of electrons = number of protons
- neutral atoms have no overall charge, but if electrons are added or removed the atom becomes charged and is now an ion
on the periodic table
atomic number - tells you how many protons
- same elements have same number of protons
- mass number = total of protons and neutrons so to get number of neutrons subtract atomic number from mass number
molecules
atoms join together to from molecules. Thy can be made from one or more elements (H2 or H20)
isotopes
isotopes are different atomic forms of the same element, which have the same number of protons but different numbers of neutrons
ie carbon-12 and carbon-13
relative atomic mass (Ar)
its the average mass of all the isotopes of an element according to their relative abundance (which can be ratio fraction or percentage)
Calculate:
- multiply the mass of each isotope by its relative abundance, add those together and divide by the sum of the relative abundace
elements contain atoms
of only one type
compouds
- two or more different elements chemically bonded together
- very difficult to separate them
- properties are totally different to properties of original elements
mixtures characteristics
- no chemical bond and can be separated by physical methods
- properties are a mixture of properties of separate parts
pure substances
- if they are made up completely of a sigle element or compound
- every pure substance has a specific sharp melting and boiling points
- mixture isn’t pure so it will boiL/ melt over a rage of temperatures
crystallisation
separates a soluble solid from a solution
- pour solution into an evaporation dish and gently heat solution, some water will evaporate and solution will get more concentrated
- once all the water has evaporated or when you start seeing crystals form (point of crystaillisation) remove dish and let solution cool
- salt will start to form crystals as it becomes insoluble in the cold, highly concentrated solution
- filter crystals out of the solution and leave in a warm place to dry. You can use a drying oven or desiccator to remove exccess water
filtration
if the product of a reaction is an insolube solid you can use filtration to separate it from the liquid reaction mixture
- it can be used in purification , for example solid impurities can be separated out of a reaction mixture using filtration
- you have to put some filter paper into a funnel and pour the mixture. The liquid runs through paper leaving behind a solid residue
rock salt separation
rock salt is a mixture of salt and sand (salt is soluble and sand is not) to separate them:
- first grind them up with pestle and mortar
- then dissolve
- then filter to separate the insoluble sand from the salt dissolved in the water
- then crystalise to separate salt from water
how cromatography separates mixtures
- different dyes move up paper at different speeds because some stick to paper while others dissolve in the solvent and travel quicker. The distace they travel depeds on solvent and paper you use
Rf value
= distance travelled by solute / distance travelled by solvent
- measure from baseline to centre of spot
- chromatography is often carried out to see if a certain substance is present in a mixture. if samples have same rf value they are likely to be the same
SRMs
chemists use samples of pure sustances called standard reference materials next to a mixture to check the identities of components, as they have controlled concentrations and purities
