Section 11 & 12 Flashcards
States of matter
Solids – strong forces of attraction between particles, regular lattice arrangement, particles don’t have much energy, have definite shape/volume
Liquids – some force of attraction, free to move past each other, same volume, some energy, hotter they get faster they move
Gases – No force of attraction, have energy, hotter they get faster they move
Changing of states
Gas to liquid = condensing Liquid to gas = evaporating Liquid to solid = freezing Solid to liquid = melting Solid to gas = subliming
Purity
A pure substance is a substance of single elements or compounds
Pure substances have specific melting and boiling points
Distillation
Used to separate liquids from the solution
1. Heat solution
2. Water vapour calls in condenser and drips into beaker
3. Water condenses and is separated
Fractional distillation – separates mixture of liquid, different liquids have different boiling points, lowest boiling point of evaporates first (goes to top of common)
Filtration and crystallisation
Filtration - separates insoluble solids from liquids, use filter paper and a funnel
Crystallisation – separates soluble solid from a solution – solution goes in evaporating dish
Chromatography
The components in the mixture separate out as mobile phase moves over stationary phase, end up in different places in stationary phase
Mobile phase – where the molecules can move (always a liquid or gas)
Stationary phase – where the molecules can’t move (solid or really thick liquid)
Rf value= distance travelled by salute ÷ distance travelled by solvent
Water treatment
Surface water – lakes, rivers
Ground water – aqua-fires (rocks the trap water underground)
Waste water – water that’s been contaminated
How water is purified in a treatment plants – Filtration – wire mesh stops large objects, sedimentation – iron/aluminium sulphate added to water (particles clump and settle to bottom)
Chlorination – chlorine gas kills bacteria
Acids and bases
Acids form H+ ions in water
Acids and bases neutralise each other
Litmus is red in acid, blue in alkali
A base is a substance that reacts with an acid to produce salt and water
Acids
Changing the concentration of an acid affects its pH
Strong acids – ionise almost completely in water
Weak acid – do not fully ionise in solution
Ionisation of a week acid is a reversible reaction
Reactions of acids
hydrogen - squeaky pop test Chlorine gas – red litmus goes white blue litmus goes red then white Oxygen – re-lights a glowing splint Carbon dioxide – limewater turns cloudy Salts form when acids react with bases
Reaction of acids equations
Acid + metal = salt + hydrogen
Acid + metal oxide = salt + water
Acid + metal carbonate = salt + water + carbon dioxide
Acid + metal hydroxide = salt + water
Making insoluble salts
Precipitation reactions - make pure dry sample of an insoluble salt - react 2 soluble salts together
Method- dissolve each salt separately in water, mix them together, filter, leave to dry
Making soluble salts
Make a soluble salt by reacting n acid containing one of the ions you want in the salt with an insoluble base that contains the other ions
You can also make them using acid/alkali reactions (do a titration)
Methord- heat acid, add base to acid, filter, heat gently in water
Rules of solubility
Nitrates = soluble
Common sulphates = soluble
Common chloride = soluble
Common salts of potassium sodium and ammonium = soluble
Common carbonates and hydroxide = insoluble
Electrolysis
Positive ions (cations) go to cathode
Negative ions (anions) go to anode
Involves oxidation and reduction
It’s the breaking down of substances using electricity
Electrolyte must be molten or dissolved as ions need to be free to move
